diff --git a/Core/StandardSamples/BoxCompositionBuilder.cpp b/Core/StandardSamples/BoxCompositionBuilder.cpp
index bcb488c463e95d179d919ec2b11bbde03a2364f9..d51e29018c50fcb42abb13a8946d509dd028fe96 100644
--- a/Core/StandardSamples/BoxCompositionBuilder.cpp
+++ b/Core/StandardSamples/BoxCompositionBuilder.cpp
@@ -35,13 +35,13 @@ MultiLayer* finalizeMultiLayer(const ParticleComposition& composition)
     ParticleLayout layout;
     layout.addParticle(composition);
 
-    Layer air_layer(refMat::Air);
+    Layer vacuum_layer(refMat::Vacuum);
     Layer middle_layer(refMat::Teflon, layer_thickness);
     middle_layer.addLayout(layout);
     Layer substrate(refMat::Substrate2);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(middle_layer);
     multi_layer->addLayer(substrate);
     return multi_layer;
diff --git a/Core/StandardSamples/BoxesSquareLatticeBuilder.cpp b/Core/StandardSamples/BoxesSquareLatticeBuilder.cpp
index 5b0722a9b4187b5adb68b1b9e4adcdacc60adf65..ae2fc01d9e8f68d915880d2b2acf41d46ec44ebf 100644
--- a/Core/StandardSamples/BoxesSquareLatticeBuilder.cpp
+++ b/Core/StandardSamples/BoxesSquareLatticeBuilder.cpp
@@ -27,7 +27,7 @@ MultiLayer* BoxesSquareLatticeBuilder::buildSample() const
     const double length = 5 * Units::nanometer;
     const double height = 10 * Units::nanometer;
 
-    Layer air_layer(refMat::Air);
+    Layer vacuum_layer(refMat::Vacuum);
     Layer substrate_layer(refMat::Substrate);
 
     std::unique_ptr<InterferenceFunction2DLattice> P_interference_function(
@@ -44,10 +44,10 @@ MultiLayer* BoxesSquareLatticeBuilder::buildSample() const
 
     particle_layout.setInterferenceFunction(*P_interference_function);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
diff --git a/Core/StandardSamples/CoreShellParticleBuilder.cpp b/Core/StandardSamples/CoreShellParticleBuilder.cpp
index cb9921012bf3af06b9297ae14f537ce2c7acbd5d..00eb213bd7e08602d680fed350d4a6c3112adf40 100644
--- a/Core/StandardSamples/CoreShellParticleBuilder.cpp
+++ b/Core/StandardSamples/CoreShellParticleBuilder.cpp
@@ -33,7 +33,7 @@ MultiLayer* CoreShellParticleBuilder::buildSample() const
     Material shell_material = HomogeneousMaterial("Shell", n_particle_shell);
     Material core_material = HomogeneousMaterial("Core", n_particle_core);
 
-    Layer air_layer(refMat::Air);
+    Layer vacuum_layer(refMat::Vacuum);
 
     FormFactorBox ff_box1(16 * Units::nanometer, 16 * Units::nanometer, 8 * Units::nanometer);
     Particle shell_particle(shell_material, ff_box1);
@@ -45,10 +45,10 @@ MultiLayer* CoreShellParticleBuilder::buildSample() const
     ParticleCoreShell particle(shell_particle, core_particle, core_position);
     ParticleLayout particle_layout(particle);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     return multi_layer;
 }
 
@@ -77,13 +77,13 @@ MultiLayer* CoreShellBoxRotateZandYBuilder::buildSample() const
     ParticleLayout layout;
     layout.addParticle(coreshell);
 
-    Layer air_layer(refMat::Air);
+    Layer vacuum_layer(refMat::Vacuum);
     Layer middle_layer(refMat::Teflon, layer_thickness);
     middle_layer.addLayout(layout);
     Layer substrate(refMat::Substrate2);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(middle_layer);
     multi_layer->addLayer(substrate);
 
diff --git a/Core/StandardSamples/CustomMorphologyBuilder.cpp b/Core/StandardSamples/CustomMorphologyBuilder.cpp
index 1a729c5a1b04ed4f7d21a1e3ad34d0d51893575f..6b9f8107fc6c60013e7f05884b143e24490f4251 100644
--- a/Core/StandardSamples/CustomMorphologyBuilder.cpp
+++ b/Core/StandardSamples/CustomMorphologyBuilder.cpp
@@ -23,7 +23,7 @@
 
 MultiLayer* CustomMorphologyBuilder::buildSample() const
 {
-    Layer air_layer(refMat::Air);
+    Layer vacuum_layer(refMat::Vacuum);
 
     ParticleLayout particle_layout;
 
@@ -97,9 +97,9 @@ MultiLayer* CustomMorphologyBuilder::buildSample() const
     p10.setPosition(pos10);
     particle_layout.addParticle(p10, 0.5);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     return multi_layer;
 }
diff --git a/Core/StandardSamples/CylindersAndPrismsBuilder.cpp b/Core/StandardSamples/CylindersAndPrismsBuilder.cpp
index e54ef4218d50fb2effaea14971f9cef46e47dc8e..8df92dba88ebd770e45c44fe9cbe4bf00793265d 100644
--- a/Core/StandardSamples/CylindersAndPrismsBuilder.cpp
+++ b/Core/StandardSamples/CylindersAndPrismsBuilder.cpp
@@ -26,7 +26,7 @@ MultiLayer* CylindersAndPrismsBuilder::buildSample() const
 {
     MultiLayer* multi_layer = new MultiLayer();
 
-    Layer air_layer(refMat::Air);
+    Layer vacuum_layer(refMat::Vacuum);
     Layer substrate_layer(refMat::Substrate);
 
     ParticleLayout particle_layout;
@@ -40,9 +40,9 @@ MultiLayer* CylindersAndPrismsBuilder::buildSample() const
     particle_layout.addParticle(cylinder, 0.5);
     particle_layout.addParticle(prism3, 0.5);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
diff --git a/Core/StandardSamples/CylindersBuilder.cpp b/Core/StandardSamples/CylindersBuilder.cpp
index e691cbf7646de3dce2abeda23d9fa872346d0fd9..d4f0897ded8b33446ab85f67e3a1018edca1a782 100644
--- a/Core/StandardSamples/CylindersBuilder.cpp
+++ b/Core/StandardSamples/CylindersBuilder.cpp
@@ -33,7 +33,7 @@ CylindersInDWBABuilder::CylindersInDWBABuilder()
 
 MultiLayer* CylindersInDWBABuilder::buildSample() const
 {
-    Layer air_layer(refMat::Air);
+    Layer vacuum_layer(refMat::Vacuum);
     Layer substrate_layer(refMat::Substrate);
 
     FormFactorCylinder ff_cylinder(m_radius, m_height);
@@ -41,10 +41,10 @@ MultiLayer* CylindersInDWBABuilder::buildSample() const
     Particle particle(refMat::Particle, ff_cylinder);
     ParticleLayout particle_layout(particle);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
@@ -61,17 +61,17 @@ CylindersInBABuilder::CylindersInBABuilder()
 
 MultiLayer* CylindersInBABuilder::buildSample() const
 {
-    Layer air_layer(refMat::Air);
+    Layer vacuum_layer(refMat::Vacuum);
 
     FormFactorCylinder ff_cylinder(m_radius, m_height);
     Particle cylinder(refMat::Particle, ff_cylinder);
 
     ParticleLayout particle_layout(cylinder);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     return multi_layer;
 }
 
@@ -85,7 +85,7 @@ LargeCylindersInDWBABuilder::LargeCylindersInDWBABuilder()
 
 MultiLayer* LargeCylindersInDWBABuilder::buildSample() const
 {
-    Layer air_layer(refMat::Air);
+    Layer vacuum_layer(refMat::Vacuum);
     Layer substrate_layer(refMat::Substrate);
 
     FormFactorCylinder ff_cylinder(m_radius, m_height);
@@ -93,10 +93,10 @@ MultiLayer* LargeCylindersInDWBABuilder::buildSample() const
     Particle particle(refMat::Particle, ff_cylinder);
     ParticleLayout particle_layout(particle);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
@@ -117,12 +117,12 @@ MultiLayer* RotatedCylindersBuilder::buildSample() const
     ParticleLayout particle_layout;
     particle_layout.addParticle(particle, 1.0, kvector_t(), RotationY(M_PI));
 
-    Layer air_layer(refMat::Air);
+    Layer vacuum_layer(refMat::Vacuum);
     Layer substrate_layer(refMat::Substrate);
     substrate_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
diff --git a/Core/StandardSamples/LatticeBuilder.cpp b/Core/StandardSamples/LatticeBuilder.cpp
index 53b83f6a8a41a71beea70c448bece19e8707588b..8e81ef4a3d2fe4a152ede3be97ff8e07c7e3a1ee 100644
--- a/Core/StandardSamples/LatticeBuilder.cpp
+++ b/Core/StandardSamples/LatticeBuilder.cpp
@@ -32,7 +32,7 @@ MultiLayer* Lattice1DBuilder::buildSample() const
     const double cylinder_height(5 * Units::nanometer);
     const double cylinder_radius(5 * Units::nanometer);
 
-    Layer air_layer(refMat::Air);
+    Layer vacuum_layer(refMat::Vacuum);
     Layer substrate_layer(refMat::Substrate);
 
     InterferenceFunction1DLattice interference_function(length, xi);
@@ -45,10 +45,10 @@ MultiLayer* Lattice1DBuilder::buildSample() const
     ParticleLayout particle_layout(cylinder);
     particle_layout.setInterferenceFunction(interference_function);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
diff --git a/Core/StandardSamples/LayersWithAbsorptionBuilder.cpp b/Core/StandardSamples/LayersWithAbsorptionBuilder.cpp
index fd114124aedf7ee0003c781d997b9feb502d729a..6184e7269266f8571fbce84a0cc3915d614d02ce 100644
--- a/Core/StandardSamples/LayersWithAbsorptionBuilder.cpp
+++ b/Core/StandardSamples/LayersWithAbsorptionBuilder.cpp
@@ -50,14 +50,14 @@ MultiLayer* LayersWithAbsorptionBuilder::buildSample() const
     ParticleLayout layout;
     layout.addParticle(particle);
 
-    Layer air_layer(refMat::Air);
+    Layer vacuum_layer(refMat::Vacuum);
     Layer middle_layer(refMat::Teflon, middle_layer_thickness);
     Layer substrate(refMat::Substrate2);
 
     middle_layer.addLayout(layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(middle_layer);
     multi_layer->addLayer(substrate);
     return multi_layer;
diff --git a/Core/StandardSamples/LayersWithAbsorptionBySLDBuilder.cpp b/Core/StandardSamples/LayersWithAbsorptionBySLDBuilder.cpp
index e78c7a1839d936a6537347ddd86e5de9194fc4bc..b5800890a83d8001975f14161c96d3c84914d0dc 100644
--- a/Core/StandardSamples/LayersWithAbsorptionBySLDBuilder.cpp
+++ b/Core/StandardSamples/LayersWithAbsorptionBySLDBuilder.cpp
@@ -25,7 +25,7 @@ const double middle_layer_thickness(60.0 * Units::nanometer);
 
 MultiLayer* LayersWithAbsorptionBySLDBuilder::buildSample() const
 {
-    Material ambience_mat = MaterialBySLD("Air", 0.0, 0.0);
+    Material ambience_mat = MaterialBySLD("Vacuum", 0.0, 0.0);
     Material middle_mat = MaterialBySLD("Teflon", 4.7573e-6, 1.6724e-12);
     Material substrate_mat = MaterialBySLD("Substrate", 2.0728e-06, 2.3747e-11);
     Material particle_mat = MaterialBySLD("Ag", 3.4682e-06, 1.0309e-08);
@@ -41,14 +41,14 @@ MultiLayer* LayersWithAbsorptionBySLDBuilder::buildSample() const
     ParticleLayout layout;
     layout.addParticle(particle);
 
-    Layer air_layer(ambience_mat);
+    Layer vacuum_layer(ambience_mat);
     Layer middle_layer(middle_mat, middle_layer_thickness);
     Layer substrate(substrate_mat);
 
     middle_layer.addLayout(layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(middle_layer);
     multi_layer->addLayer(substrate);
     return multi_layer;
diff --git a/Core/StandardSamples/MagneticLayersBuilder.cpp b/Core/StandardSamples/MagneticLayersBuilder.cpp
index 7013eb9c6aecbca80d3166dc7a658d465ba480be..b67b733c812665beb0472cde94e9c19ef6afcf7c 100644
--- a/Core/StandardSamples/MagneticLayersBuilder.cpp
+++ b/Core/StandardSamples/MagneticLayersBuilder.cpp
@@ -34,7 +34,7 @@ MultiLayer* MagneticSubstrateZeroFieldBuilder::buildSample() const
 {
     kvector_t substr_field(0.0, 0.0, 0.0);
     kvector_t particle_field(0.1, 0.0, 0.0);
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material substrate_material = HomogeneousMaterial("Substrate", 7e-6, 2e-8, substr_field);
     Material particle_material = HomogeneousMaterial("MagParticle", 6e-4, 2e-8, particle_field);
 
@@ -44,12 +44,12 @@ MultiLayer* MagneticSubstrateZeroFieldBuilder::buildSample() const
     Particle particle(particle_material, ff_sphere);
     particle_layout.addParticle(particle, 1.0, position);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer substrate_layer(substrate_material);
     substrate_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
@@ -59,15 +59,15 @@ MultiLayer* SimpleMagneticLayerBuilder::buildSample() const
     MultiLayer* multi_layer = new MultiLayer();
 
     kvector_t layer_field = kvector_t(0.0, 1e8, 0.0);
-    Material air_material = MaterialBySLD("Air", 0.0, 0.0);
+    Material vacuum_material = MaterialBySLD("Vacuum", 0.0, 0.0);
     Material layer_material = MaterialBySLD("MagLayer", 1e-4, 1e-8, layer_field);
     Material substrate_material = MaterialBySLD("Substrate", 7e-5, 2e-6);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer intermediate_layer(layer_material, 10.0); // 10 nm layer thickness
     Layer substrate_layer(substrate_material);
 
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(intermediate_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
@@ -79,8 +79,8 @@ MultiLayer* MagneticLayerBuilder::buildSample() const
 
     kvector_t layer_field = kvector_t(0.0, 0.0, 1e6);
     kvector_t particle_field(1e6, 0.0, 0.0);
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
-    Material layer_material = HomogeneousMaterial("Air", 0.0, 0.0, layer_field);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
+    Material layer_material = HomogeneousMaterial("Vacuum", 0.0, 0.0, layer_field);
     Material substrate_material = HomogeneousMaterial("Substrate", 7e-6, 2e-8);
     Material particle_material = HomogeneousMaterial("MagParticle", 6e-4, 2e-8, particle_field);
 
@@ -89,12 +89,12 @@ MultiLayer* MagneticLayerBuilder::buildSample() const
     Particle particle(particle_material, ff_sphere);
     particle_layout.addParticle(particle, 1.0);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer intermediate_layer(layer_material);
     intermediate_layer.addLayout(particle_layout);
     Layer substrate_layer(substrate_material);
 
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(intermediate_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
@@ -112,17 +112,17 @@ MultiLayer* SimpleMagneticRotationBuilder::builder(double sigmaRoughness,
 
     kvector_t substr_field = kvector_t(0.0, 1e6, 0.0);
     kvector_t layer_field = kvector_t(1e6, 1e6, 0.0);
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material substrate_material = HomogeneousMaterial("Substrate", 7e-6, 2e-8, substr_field);
     Material layer_material = HomogeneousMaterial("MagLayer", 6e-4, 2e-8, layer_field);
 
     auto roughness = LayerRoughness();
     roughness.setSigma(sigmaRoughness * Units::angstrom);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer substrate_layer(substrate_material);
     Layer layer(layer_material, 200 * Units::angstrom);
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayerWithTopRoughness(layer, roughness);
     multi_layer->addLayerWithTopRoughness(substrate_layer, roughness);
     multi_layer->setRoughnessModel(roughnessModel);
@@ -160,7 +160,7 @@ MultiLayer* MagneticRotationBuilder::buildSample() const
 
     kvector_t substr_field = kvector_t(0.0, 1e6, 0.0);
     kvector_t particle_field(1e6, 0.0, 0.0);
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material substrate_material = HomogeneousMaterial("Substrate", 7e-6, 2e-8, substr_field);
     Material particle_material = HomogeneousMaterial("MagParticle", 6e-4, 2e-8, particle_field);
 
@@ -171,11 +171,11 @@ MultiLayer* MagneticRotationBuilder::buildSample() const
     RotationZ rot_z(90 * Units::deg);
     particle_layout.addParticle(particle, 1.0, position, rot_z);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer substrate_layer(substrate_material);
     substrate_layer.addLayout(particle_layout);
 
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
diff --git a/Core/StandardSamples/MagneticParticlesBuilder.cpp b/Core/StandardSamples/MagneticParticlesBuilder.cpp
index 5d0b90dbf377e6e26fb58e024c34b740f332535d..87a2148d58b32e6399a9feaa1b7cb459b6386c01 100644
--- a/Core/StandardSamples/MagneticParticlesBuilder.cpp
+++ b/Core/StandardSamples/MagneticParticlesBuilder.cpp
@@ -33,12 +33,12 @@ MultiLayer* MagneticParticleZeroFieldBuilder::buildSample() const
     const double m_cylinder_radius(5 * Units::nanometer);
     const double m_cylinder_height(5 * Units::nanometer);
 
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material substrate_material = HomogeneousMaterial("Substrate", 6e-6, 2e-8);
     kvector_t magnetic_field(0.0, 0.0, 0.0);
     Material particle_material = HomogeneousMaterial("MagParticle", 6e-4, 2e-8, magnetic_field);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer substrate_layer(substrate_material);
 
     FormFactorCylinder ff_cylinder(m_cylinder_radius, m_cylinder_height);
@@ -46,10 +46,10 @@ MultiLayer* MagneticParticleZeroFieldBuilder::buildSample() const
     Particle particle(particle_material, ff_cylinder);
     ParticleLayout particle_layout(particle);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
@@ -63,12 +63,12 @@ MultiLayer* MagneticCylindersBuilder::buildSample() const
     const double m_cylinder_radius(5 * Units::nanometer);
     const double m_cylinder_height(5 * Units::nanometer);
 
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material substrate_material = HomogeneousMaterial("Substrate", 15e-6, 0.0);
     kvector_t magnetization(0.0, 1e6, 0.0);
     Material particle_material = HomogeneousMaterial("MagParticle2", 5e-6, 0.0, magnetization);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer substrate_layer(substrate_material);
 
     FormFactorCylinder ff_cylinder(m_cylinder_radius, m_cylinder_height);
@@ -76,10 +76,10 @@ MultiLayer* MagneticCylindersBuilder::buildSample() const
     Particle particle(particle_material, ff_cylinder);
     ParticleLayout particle_layout(particle);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
@@ -94,7 +94,7 @@ MultiLayer* MagneticSpheresBuilder::buildSample() const
 
     kvector_t magnetization(0.0, 0.0, 1e7);
     Material particle_material = HomogeneousMaterial("Particle", 2e-5, 4e-7, magnetization);
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material substrate_material = HomogeneousMaterial("Substrate", 7e-6, 1.8e-7);
 
     FormFactorFullSphere ff_sphere(m_sphere_radius);
@@ -104,12 +104,12 @@ MultiLayer* MagneticSpheresBuilder::buildSample() const
     ParticleLayout particle_layout;
     particle_layout.addParticle(particle, 1.0, position);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer substrate_layer(substrate_material);
     substrate_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
diff --git a/Core/StandardSamples/MesoCrystalBuilder.cpp b/Core/StandardSamples/MesoCrystalBuilder.cpp
index 17ed0649dc8f115bf7d463dc61638b310f69e1e3..4b5c959e050b4c13a94ace71d9dc3063d5ea36fd 100644
--- a/Core/StandardSamples/MesoCrystalBuilder.cpp
+++ b/Core/StandardSamples/MesoCrystalBuilder.cpp
@@ -46,12 +46,12 @@ MultiLayer* MesoCrystalBuilder::buildSample() const
     ParticleLayout particle_layout;
     particle_layout.addParticle(meso);
 
-    Layer air_layer(refMat::Air);
-    air_layer.addLayout(particle_layout);
+    Layer vacuum_layer(refMat::Vacuum);
+    vacuum_layer.addLayout(particle_layout);
     Layer substrate_layer(refMat::Substrate);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
diff --git a/Core/StandardSamples/MultiLayerWithRoughnessBuilder.cpp b/Core/StandardSamples/MultiLayerWithRoughnessBuilder.cpp
index e275672595ff541a3909848cd06569468b0ae331..28fcc32a19689f7d4d1a56bc9b3f5ef9492cbb14 100644
--- a/Core/StandardSamples/MultiLayerWithRoughnessBuilder.cpp
+++ b/Core/StandardSamples/MultiLayerWithRoughnessBuilder.cpp
@@ -28,12 +28,12 @@ MultiLayer* MultiLayerWithRoughnessBuilder::buildSample() const
     const double lateralCorrLength(5.0 * Units::nanometer);
     const double crossCorrLength(10.0 * Units::nanometer);
 
-    Material air_material = HomogeneousMaterial("Air", 0., 0.);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0., 0.);
     Material substrate_material = HomogeneousMaterial("Substrate", 15e-6, 0.0);
     Material part_a_material = HomogeneousMaterial("PartA", 5e-6, 0.0);
     Material part_b_material = HomogeneousMaterial("PartB", 10e-6, 0.0);
 
-    Layer air_layer(air_material, 0);
+    Layer vacuum_layer(vacuum_material, 0);
     Layer partA_layer(part_a_material, thicknessA);
     Layer partB_layer(part_b_material, thicknessB);
     Layer substrate_layer(substrate_material, 0);
@@ -41,7 +41,7 @@ MultiLayer* MultiLayerWithRoughnessBuilder::buildSample() const
     LayerRoughness roughness(sigma, hurst, lateralCorrLength);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     for (int i = 0; i < 5; ++i) {
         multi_layer->addLayerWithTopRoughness(partA_layer, roughness);
         multi_layer->addLayerWithTopRoughness(partB_layer, roughness);
diff --git a/Core/StandardSamples/MultipleLayoutBuilder.cpp b/Core/StandardSamples/MultipleLayoutBuilder.cpp
index 279e477be01d6265803f41089ae017357a4c935c..4e68ea1cbdcbf06936f625985bf3e444eba93277 100644
--- a/Core/StandardSamples/MultipleLayoutBuilder.cpp
+++ b/Core/StandardSamples/MultipleLayoutBuilder.cpp
@@ -30,7 +30,7 @@ MultiLayer* MultipleLayoutBuilder::buildSample() const
     const double prislength(10 * Units::nanometer);
     const double cylinder_weight(0.5);
 
-    Layer air_layer(refMat::Air);
+    Layer vacuum_layer(refMat::Vacuum);
     Layer substrate_layer(refMat::Substrate);
 
     ParticleLayout particle_layout_1;
@@ -45,11 +45,11 @@ MultiLayer* MultipleLayoutBuilder::buildSample() const
     particle_layout_1.addParticle(cylinder, cylinder_weight);
     particle_layout_2.addParticle(prism3, 1.0 - cylinder_weight);
 
-    air_layer.addLayout(particle_layout_1);
-    air_layer.addLayout(particle_layout_2);
+    vacuum_layer.addLayout(particle_layout_1);
+    vacuum_layer.addLayout(particle_layout_2);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
diff --git a/Core/StandardSamples/ParaCrystalBuilder.cpp b/Core/StandardSamples/ParaCrystalBuilder.cpp
index d44e395e738ba5724960a900eaf401cc3f04f81f..3b910b7085aa0eb81f2b64b95a8a1540934e6305 100644
--- a/Core/StandardSamples/ParaCrystalBuilder.cpp
+++ b/Core/StandardSamples/ParaCrystalBuilder.cpp
@@ -34,7 +34,7 @@ MultiLayer* RadialParaCrystalBuilder::buildSample() const
     const double m_cylinder_height(5 * Units::nanometer);
     const double m_cylinder_radius(5 * Units::nanometer);
 
-    Layer air_layer(refMat::Air);
+    Layer vacuum_layer(refMat::Vacuum);
     Layer substrate_layer(refMat::Substrate);
 
     InterferenceFunctionRadialParaCrystal interference_function(m_corr_peak_distance,
@@ -47,10 +47,10 @@ MultiLayer* RadialParaCrystalBuilder::buildSample() const
     ParticleLayout particle_layout(particle);
     particle_layout.setInterferenceFunction(interference_function);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
@@ -69,7 +69,7 @@ Basic2DParaCrystalBuilder::~Basic2DParaCrystalBuilder() = default;
 
 MultiLayer* Basic2DParaCrystalBuilder::buildSample() const
 {
-    Layer air_layer(refMat::Air);
+    Layer vacuum_layer(refMat::Vacuum);
     Layer substrate_layer(refMat::Substrate);
 
     InterferenceFunction2DParaCrystal interference_function(
@@ -86,10 +86,10 @@ MultiLayer* Basic2DParaCrystalBuilder::buildSample() const
     ParticleLayout particle_layout(particle);
     particle_layout.setInterferenceFunction(interference_function);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
@@ -119,7 +119,7 @@ MultiLayer* HexParaCrystalBuilder::buildSample() const
     const double m_cylinder_height(5 * Units::nanometer);
     const double m_cylinder_radius(5 * Units::nanometer);
 
-    Layer air_layer(refMat::Air);
+    Layer vacuum_layer(refMat::Vacuum);
     Layer substrate_layer(refMat::Substrate);
 
     std::unique_ptr<InterferenceFunction2DParaCrystal> P_interference_function{
@@ -134,10 +134,10 @@ MultiLayer* HexParaCrystalBuilder::buildSample() const
     ParticleLayout particle_layout(cylinder);
     particle_layout.setInterferenceFunction(*P_interference_function);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
@@ -148,7 +148,7 @@ MultiLayer* HexParaCrystalBuilder::buildSample() const
 
 MultiLayer* RectParaCrystalBuilder::buildSample() const
 {
-    Layer air_layer(refMat::Air);
+    Layer vacuum_layer(refMat::Vacuum);
     Layer substrate_layer(refMat::Substrate);
 
     std::unique_ptr<InterferenceFunction2DParaCrystal> P_interference_function{
@@ -166,10 +166,10 @@ MultiLayer* RectParaCrystalBuilder::buildSample() const
     ParticleLayout particle_layout(particle);
     particle_layout.setInterferenceFunction(*P_interference_function);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
diff --git a/Core/StandardSamples/ParticleCompositionBuilder.cpp b/Core/StandardSamples/ParticleCompositionBuilder.cpp
index fbd543ce02bacdefb73cca33aa810f854a2ee55b..b6096bdfe97b4b0c6e62399ce22b5b4014b16f69 100644
--- a/Core/StandardSamples/ParticleCompositionBuilder.cpp
+++ b/Core/StandardSamples/ParticleCompositionBuilder.cpp
@@ -27,11 +27,11 @@
 
 MultiLayer* ParticleCompositionBuilder::buildSample() const
 {
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material substrate_material = HomogeneousMaterial("Substrate", 6e-6, 2e-8);
     Material particle_material = HomogeneousMaterial("Particle", 6e-4, 2e-8);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer substrate_layer(substrate_material);
 
     double radius(10.0 * Units::nanometer);
@@ -55,10 +55,10 @@ MultiLayer* ParticleCompositionBuilder::buildSample() const
 
     particle_layout.setInterferenceFunction(*P_interference);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
diff --git a/Core/StandardSamples/ParticleDistributionsBuilder.cpp b/Core/StandardSamples/ParticleDistributionsBuilder.cpp
index 6e74aad2eb1de1ba077d4b0bb1a5e1d01a99d6d4..cddfcef431676f21c9cd5276766ec83d1ebabdcd 100644
--- a/Core/StandardSamples/ParticleDistributionsBuilder.cpp
+++ b/Core/StandardSamples/ParticleDistributionsBuilder.cpp
@@ -34,10 +34,10 @@ MultiLayer* CylindersWithSizeDistributionBuilder::buildSample() const
     const double height(5 * Units::nanometer);
     const double radius(5 * Units::nanometer);
 
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material particle_material = HomogeneousMaterial("Particle", 6e-4, 2e-8);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
 
     ParticleLayout particle_layout;
     // preparing prototype of nano particle
@@ -56,10 +56,10 @@ MultiLayer* CylindersWithSizeDistributionBuilder::buildSample() const
     ParticleDistribution particle_collection(nano_particle, par_distr);
     particle_layout.addParticle(particle_collection);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     return multi_layer;
 }
 
@@ -77,10 +77,10 @@ TwoTypesCylindersDistributionBuilder::TwoTypesCylindersDistributionBuilder()
 MultiLayer* TwoTypesCylindersDistributionBuilder::buildSample() const
 {
 
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material particle_material = HomogeneousMaterial("Particle", 6e-4, 2e-8);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
 
     ParticleLayout particle_layout;
 
@@ -113,10 +113,10 @@ MultiLayer* TwoTypesCylindersDistributionBuilder::buildSample() const
     ParticleDistribution particle_collection2(cylinder2, par_distr2);
     particle_layout.addParticle(particle_collection2, 0.05);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     return multi_layer;
 }
 
@@ -130,7 +130,7 @@ RotatedPyramidsDistributionBuilder::RotatedPyramidsDistributionBuilder()
 
 MultiLayer* RotatedPyramidsDistributionBuilder::buildSample() const
 {
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material substrate_material = HomogeneousMaterial("Substrate", 6e-6, 2e-8);
     Material particle_material = HomogeneousMaterial("Particle", 6e-4, 2e-8);
 
@@ -149,13 +149,13 @@ MultiLayer* RotatedPyramidsDistributionBuilder::buildSample() const
     particle_layout.addParticle(collection);
 
     // Multi layer
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer substrate_layer(substrate_material);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
@@ -164,7 +164,7 @@ MultiLayer* RotatedPyramidsDistributionBuilder::buildSample() const
 
 MultiLayer* SpheresWithLimitsDistributionBuilder::buildSample() const
 {
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material substrate_material = HomogeneousMaterial("Substrate", 6e-6, 2e-8);
     Material particle_material = HomogeneousMaterial("Particle", 6e-4, 2e-8);
 
@@ -183,13 +183,13 @@ MultiLayer* SpheresWithLimitsDistributionBuilder::buildSample() const
     particle_layout.addParticle(collection);
 
     // Multi layer
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer substrate_layer(substrate_material);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
 
     return multi_layer;
@@ -199,7 +199,7 @@ MultiLayer* SpheresWithLimitsDistributionBuilder::buildSample() const
 
 MultiLayer* ConesWithLimitsDistributionBuilder::buildSample() const
 {
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material substrate_material = HomogeneousMaterial("Substrate", 6e-6, 2e-8);
     Material particle_material = HomogeneousMaterial("Particle", 6e-4, 2e-8);
 
@@ -219,20 +219,20 @@ MultiLayer* ConesWithLimitsDistributionBuilder::buildSample() const
     particle_layout.addParticle(collection);
 
     // Multi layer
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer substrate_layer(substrate_material);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
 
 MultiLayer* LinkedBoxDistributionBuilder::buildSample() const
 {
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material substrate_material = HomogeneousMaterial("Substrate", 6e-6, 2e-8);
     Material particle_material = HomogeneousMaterial("Particle", 6e-4, 2e-8);
 
@@ -253,13 +253,13 @@ MultiLayer* LinkedBoxDistributionBuilder::buildSample() const
     particle_layout.setTotalParticleSurfaceDensity(1e-4);
 
     // Multi layer
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer substrate_layer(substrate_material);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
diff --git a/Core/StandardSamples/ParticleInTheAirBuilder.cpp b/Core/StandardSamples/ParticleInTheAirBuilder.cpp
index 5d9c83b753a5fb23a328981023bdabaae1422e77..e02388f8d84cf11db5649107f3c8a5369f9cf77f 100644
--- a/Core/StandardSamples/ParticleInTheAirBuilder.cpp
+++ b/Core/StandardSamples/ParticleInTheAirBuilder.cpp
@@ -34,17 +34,17 @@ ParticleInTheAirBuilder::ParticleInTheAirBuilder()
 
 MultiLayer* ParticleInTheAirBuilder::buildSample() const
 {
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material particle_material = HomogeneousMaterial("Particle", 6e-4, 2e-8);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
 
     Particle particle(particle_material, *m_ff);
     ParticleLayout particle_layout(particle);
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* result = new MultiLayer;
-    result->addLayer(air_layer);
+    result->addLayer(vacuum_layer);
     return result;
 }
 
diff --git a/Core/StandardSamples/PercusYevickBuilder.cpp b/Core/StandardSamples/PercusYevickBuilder.cpp
index 3eed8f3a39ed4e93206a38844e5679cc28e4e0bf..e08c78897c5eb378d93a53d188b566058b6fb271 100644
--- a/Core/StandardSamples/PercusYevickBuilder.cpp
+++ b/Core/StandardSamples/PercusYevickBuilder.cpp
@@ -29,11 +29,11 @@ MultiLayer* HardDiskBuilder::buildSample() const
     const double m_disk_radius(5 * Units::nanometer);
     const double m_density(0.006);
 
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material substrate_material = HomogeneousMaterial("Substrate", 6e-6, 2e-8);
     Material particle_material = HomogeneousMaterial("Particle", 6e-4, 2e-8);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer substrate_layer(substrate_material);
 
     FormFactorCylinder ff_cylinder(m_cylinder_radius, m_cylinder_height);
@@ -43,10 +43,10 @@ MultiLayer* HardDiskBuilder::buildSample() const
     InterferenceFunctionHardDisk interference_function(m_disk_radius, m_density);
     particle_layout.setInterferenceFunction(interference_function);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
diff --git a/Core/StandardSamples/ReferenceMaterials.h b/Core/StandardSamples/ReferenceMaterials.h
index 18c6abd6c2527a5a3021af3e4d61bb7c30c16de7..c75b1a7e22d279a5188a8d43763006e40e3a427d 100644
--- a/Core/StandardSamples/ReferenceMaterials.h
+++ b/Core/StandardSamples/ReferenceMaterials.h
@@ -21,7 +21,7 @@
 
 namespace refMat {
 
-static const Material Air = HomogeneousMaterial("Air", 0.0, 0.0);
+static const Material Vacuum = HomogeneousMaterial("Vacuum", 0.0, 0.0);
 static const Material Substrate = HomogeneousMaterial("Substrate", 6e-6, 2e-8);
 static const Material Particle = HomogeneousMaterial("Particle", 6e-4, 2e-8);
 
diff --git a/Core/StandardSamples/RipplesBuilder.cpp b/Core/StandardSamples/RipplesBuilder.cpp
index 11a298474dc31f16e00a40be34a579d6d0426c92..e2676f57556347101f42ca55cc6a6aff81381881 100644
--- a/Core/StandardSamples/RipplesBuilder.cpp
+++ b/Core/StandardSamples/RipplesBuilder.cpp
@@ -26,11 +26,11 @@
 MultiLayer* CosineRippleBuilder::buildSample() const
 {
 
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material substrate_material = HomogeneousMaterial("Substrate", 6e-6, 2e-8);
     Material particle_material = HomogeneousMaterial("Particle", 6e-4, 2e-8);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     FormFactorCosineRippleBox ff_ripple1(100.0, 20.0, 4.0);
     Particle ripple(particle_material, ff_ripple1);
 
@@ -41,12 +41,12 @@ MultiLayer* CosineRippleBuilder::buildSample() const
     interference_function.setProbabilityDistribution(pdf);
     particle_layout.setInterferenceFunction(interference_function);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     Layer substrate_layer(substrate_material);
 
     MultiLayer* p_multi_layer = new MultiLayer();
-    p_multi_layer->addLayer(air_layer);
+    p_multi_layer->addLayer(vacuum_layer);
     p_multi_layer->addLayer(substrate_layer);
     return p_multi_layer;
 }
@@ -60,11 +60,11 @@ TriangularRippleBuilder::TriangularRippleBuilder() : m_d(0.0 * Units::nanometer)
 
 MultiLayer* TriangularRippleBuilder::buildSample() const
 {
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material substrate_material = HomogeneousMaterial("Substrate", 6e-6, 2e-8);
     Material particle_material = HomogeneousMaterial("Particle", 6e-4, 2e-8);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     FormFactorSawtoothRippleBox ff_ripple2(100.0, 20.0, 4.0, m_d);
     Particle ripple(particle_material, ff_ripple2);
 
@@ -75,11 +75,11 @@ MultiLayer* TriangularRippleBuilder::buildSample() const
     interference_function.setProbabilityDistribution(pdf);
     particle_layout.setInterferenceFunction(interference_function);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
     Layer substrate_layer(substrate_material);
 
     MultiLayer* p_multi_layer = new MultiLayer();
-    p_multi_layer->addLayer(air_layer);
+    p_multi_layer->addLayer(vacuum_layer);
     p_multi_layer->addLayer(substrate_layer);
     return p_multi_layer;
 }
diff --git a/Core/StandardSamples/RotatedPyramidsBuilder.cpp b/Core/StandardSamples/RotatedPyramidsBuilder.cpp
index d46c3d9b5e567a6a5685a15d5abaeb6dc0a5f98f..643545be84a0fbdba8b36344f09686b1ed5b4b1b 100644
--- a/Core/StandardSamples/RotatedPyramidsBuilder.cpp
+++ b/Core/StandardSamples/RotatedPyramidsBuilder.cpp
@@ -28,11 +28,11 @@ MultiLayer* RotatedPyramidsBuilder::buildSample() const
     const double m_alpha(Units::deg2rad(54.73));
     const double m_zangle(45. * Units::degree);
 
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material substrate_material = HomogeneousMaterial("Substrate", 6e-6, 2e-8);
     Material particle_material = HomogeneousMaterial("Particle", 6e-4, 2e-8);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer substrate_layer(substrate_material);
 
     FormFactorPyramid ff_pyramid(m_length, m_height, m_alpha);
@@ -44,10 +44,10 @@ MultiLayer* RotatedPyramidsBuilder::buildSample() const
     ParticleLayout particle_layout;
     particle_layout.addParticle(pyramid, 1.0, kvector_t(0, 0, 0), z_rotation);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
diff --git a/Core/StandardSamples/SizeDistributionModelsBuilder.cpp b/Core/StandardSamples/SizeDistributionModelsBuilder.cpp
index 4ed86796ad819de8f9a566e210025823e160892a..4587fa62e9c54d9295549c857bca5c540fe46584 100644
--- a/Core/StandardSamples/SizeDistributionModelsBuilder.cpp
+++ b/Core/StandardSamples/SizeDistributionModelsBuilder.cpp
@@ -29,7 +29,7 @@ MultiLayer* SizeDistributionDAModelBuilder::buildSample() const
 {
     MultiLayer* multi_layer = new MultiLayer();
 
-    Material m_ambience = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material m_ambience = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material m_substrate = HomogeneousMaterial("Substrate", 6e-6, 2e-8);
     Material m_particle = HomogeneousMaterial("Particle", 6e-4, 2e-8);
 
@@ -57,11 +57,11 @@ MultiLayer* SizeDistributionDAModelBuilder::buildSample() const
     particle_layout.addParticle(cylinder2, 0.2);
     particle_layout.setInterferenceFunction(interference);
 
-    Layer air_layer(m_ambience);
-    air_layer.addLayout(particle_layout);
+    Layer vacuum_layer(m_ambience);
+    vacuum_layer.addLayout(particle_layout);
     Layer substrate_layer(m_substrate);
 
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
@@ -72,7 +72,7 @@ MultiLayer* SizeDistributionLMAModelBuilder::buildSample() const
 {
     MultiLayer* multi_layer = new MultiLayer();
 
-    Material m_ambience = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material m_ambience = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material m_substrate = HomogeneousMaterial("Substrate", 6e-6, 2e-8);
     Material m_particle = HomogeneousMaterial("Particle", 6e-4, 2e-8);
 
@@ -108,12 +108,12 @@ MultiLayer* SizeDistributionLMAModelBuilder::buildSample() const
     particle_layout2.addParticle(cylinder2, 0.2);
     particle_layout2.setInterferenceFunction(interference2);
 
-    Layer air_layer(m_ambience);
-    air_layer.addLayout(particle_layout1);
-    air_layer.addLayout(particle_layout2);
+    Layer vacuum_layer(m_ambience);
+    vacuum_layer.addLayout(particle_layout1);
+    vacuum_layer.addLayout(particle_layout2);
     Layer substrate_layer(m_substrate);
 
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
 
     return multi_layer;
@@ -125,7 +125,7 @@ MultiLayer* SizeDistributionSSCAModelBuilder::buildSample() const
 {
     MultiLayer* multi_layer = new MultiLayer();
 
-    Material m_ambience = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material m_ambience = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material m_substrate = HomogeneousMaterial("Substrate", 6e-6, 2e-8);
     Material m_particle = HomogeneousMaterial("Particle", 6e-4, 2e-8);
 
@@ -154,11 +154,11 @@ MultiLayer* SizeDistributionSSCAModelBuilder::buildSample() const
     particle_layout.addParticle(cylinder2, 0.2);
     particle_layout.setInterferenceFunction(interference);
 
-    Layer air_layer(m_ambience);
-    air_layer.addLayout(particle_layout);
+    Layer vacuum_layer(m_ambience);
+    vacuum_layer.addLayout(particle_layout);
     Layer substrate_layer(m_substrate);
 
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
 
     return multi_layer;
@@ -170,10 +170,10 @@ MultiLayer* CylindersInSSCABuilder::buildSample() const
 {
     MultiLayer* multi_layer = new MultiLayer();
 
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material particle_material = HomogeneousMaterial("Particle", 6e-4, 2e-8);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
 
     InterferenceFunctionRadialParaCrystal interference_function(15.0 * Units::nanometer,
                                                                 1e3 * Units::nanometer);
@@ -197,8 +197,8 @@ MultiLayer* CylindersInSSCABuilder::buildSample() const
 
     particle_layout.setInterferenceFunction(interference_function);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     return multi_layer;
 }
diff --git a/Core/StandardSamples/SlicedCompositionBuilder.cpp b/Core/StandardSamples/SlicedCompositionBuilder.cpp
index a07eef99a54294fb94d83f051e294c6925925408..716eba52b708c24bfdfcdbf55af5f54486896249 100644
--- a/Core/StandardSamples/SlicedCompositionBuilder.cpp
+++ b/Core/StandardSamples/SlicedCompositionBuilder.cpp
@@ -26,7 +26,7 @@ MultiLayer* SlicedCompositionBuilder::buildSample() const
 {
     MultiLayer* p_multi_layer = new MultiLayer();
 
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material substrate_material = HomogeneousMaterial("Substrate", 3.212e-6, 3.244e-8);
     Material topCupMaterial = HomogeneousMaterial("Ag", 1.245e-5, 5.419e-7);
     Material bottomCupMaterial = HomogeneousMaterial("Teflon", 2.900e-6, 6.019e-9);
@@ -49,12 +49,12 @@ MultiLayer* SlicedCompositionBuilder::buildSample() const
     ParticleLayout particle_layout;
     particle_layout.addParticle(composition);
 
-    Layer air_layer(air_material);
-    air_layer.addLayout(particle_layout);
+    Layer vacuum_layer(vacuum_material);
+    vacuum_layer.addLayout(particle_layout);
 
     Layer substrate_layer(substrate_material);
 
-    p_multi_layer->addLayer(air_layer);
+    p_multi_layer->addLayer(vacuum_layer);
     p_multi_layer->addLayer(substrate_layer);
 
     return p_multi_layer;
diff --git a/Core/StandardSamples/SlicedCylindersBuilder.cpp b/Core/StandardSamples/SlicedCylindersBuilder.cpp
index fb136d7fa053e825580319a5bf14afd5f662bb3e..377cbf9bb0cdf7b5ff695e80fddee57f6d5ea355 100644
--- a/Core/StandardSamples/SlicedCylindersBuilder.cpp
+++ b/Core/StandardSamples/SlicedCylindersBuilder.cpp
@@ -45,11 +45,11 @@ complex_t averageSLD(complex_t sld_p, complex_t sld_l, double eff_vol)
 
 MultiLayer* SlicedCylindersBuilder::buildSample() const
 {
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material substrate_material = HomogeneousMaterial("Substrate", 6e-6, 2e-8);
     Material particle_material = HomogeneousMaterial("Particle", 6e-4, 2e-8);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer substrate_layer(substrate_material);
 
     FormFactorCylinder ff_cylinder(radius, height);
@@ -57,24 +57,24 @@ MultiLayer* SlicedCylindersBuilder::buildSample() const
     Particle particle(particle_material, ff_cylinder);
     ParticleLayout particle_layout(particle);
 
-    air_layer.addLayout(particle_layout);
-    air_layer.setNumberOfSlices(n_slices);
+    vacuum_layer.addLayout(particle_layout);
+    vacuum_layer.setNumberOfSlices(n_slices);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
 
 MultiLayer* SLDSlicedCylindersBuilder::buildSample() const
 {
-    Material air_material = MaterialBySLD("Air", 0.0, 0.0);
+    Material vacuum_material = MaterialBySLD("Vacuum", 0.0, 0.0);
     complex_t sub_sld = getSLDFromN(wavelength, 6e-6, 2e-8);
     Material substrate_material = MaterialBySLD("Substrate", sub_sld.real(), sub_sld.imag());
     complex_t par_sld = getSLDFromN(wavelength, 6e-4, 2e-8);
     Material particle_material = MaterialBySLD("Particle", par_sld.real(), par_sld.imag());
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer substrate_layer(substrate_material);
 
     FormFactorCylinder ff_cylinder(radius, height);
@@ -82,11 +82,11 @@ MultiLayer* SLDSlicedCylindersBuilder::buildSample() const
     Particle particle(particle_material, ff_cylinder);
     ParticleLayout particle_layout(particle);
 
-    air_layer.addLayout(particle_layout);
-    air_layer.setNumberOfSlices(n_slices);
+    vacuum_layer.addLayout(particle_layout);
+    vacuum_layer.setNumberOfSlices(n_slices);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
@@ -95,22 +95,22 @@ MultiLayer* AveragedSlicedCylindersBuilder::buildSample() const
 {
     const auto par_surf_density = ParticleLayout().totalParticleSurfaceDensity();
 
-    complex_t air_sld{0.0, 0.0};
-    Material air_material = MaterialBySLD("Air", air_sld.real(), air_sld.imag());
+    complex_t vacuum_sld{0.0, 0.0};
+    Material vacuum_material = MaterialBySLD("Vacuum", vacuum_sld.real(), vacuum_sld.imag());
     complex_t sub_sld = getSLDFromN(wavelength, 6e-6, 2e-8);
     Material substrate_material = MaterialBySLD("Substrate", sub_sld.real(), sub_sld.imag());
 
     double eff_vol = par_surf_density * M_PI * radius * radius;
     complex_t par_sld = getSLDFromN(wavelength, 6e-4, 2e-8);
-    complex_t avr_sld = averageSLD(par_sld, air_sld, eff_vol);
+    complex_t avr_sld = averageSLD(par_sld, vacuum_sld, eff_vol);
     Material avr_material = MaterialBySLD("Avr", avr_sld.real(), avr_sld.imag());
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer avr_layer(avr_material, height / n_slices);
     Layer substrate_layer(substrate_material);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     for (size_t i = 0; i < n_slices; ++i)
         multi_layer->addLayer(avr_layer);
     multi_layer->addLayer(substrate_layer);
diff --git a/Core/StandardSamples/ThickAbsorptiveSampleBuilder.cpp b/Core/StandardSamples/ThickAbsorptiveSampleBuilder.cpp
index 9e1de910ca3c806d849fd7329475aef800fc5646..ca9ed4ea23ba856a5682cbd396df74412d66d9db 100644
--- a/Core/StandardSamples/ThickAbsorptiveSampleBuilder.cpp
+++ b/Core/StandardSamples/ThickAbsorptiveSampleBuilder.cpp
@@ -21,21 +21,21 @@
 
 MultiLayer* ThickAbsorptiveSampleBuilder::buildSample() const
 {
-    Material air_material = MaterialBySLD("Air", 0.0, 0.0);
+    Material vacuum_material = MaterialBySLD("Vacuum", 0.0, 0.0);
     Material au_material = MaterialBySLD("Au", 3.48388057043e-05, 1.79057609656e-05);
     Material si_material = MaterialBySLD("Si", 3.84197565094e-07, 6.28211531498e-07);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer au_layer(au_material, 200.0);
-    Layer air_layer_2(air_material, 10.0);
+    Layer vacuum_layer_2(vacuum_material, 10.0);
     Layer substrate_layer(si_material);
 
     LayerRoughness rough(5.0, 0.5, 10.0);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(au_layer);
-    multi_layer->addLayer(air_layer_2);
+    multi_layer->addLayer(vacuum_layer_2);
     multi_layer->addLayerWithTopRoughness(substrate_layer, rough);
     return multi_layer;
 }
diff --git a/Core/StandardSamples/TransformationsBuilder.cpp b/Core/StandardSamples/TransformationsBuilder.cpp
index 0817f48b606cec4606f952875490c2b312101291..b62211fa491fa80fec10547ec669b02604321360 100644
--- a/Core/StandardSamples/TransformationsBuilder.cpp
+++ b/Core/StandardSamples/TransformationsBuilder.cpp
@@ -23,7 +23,7 @@
 
 MultiLayer* TransformBoxBuilder::buildSample() const
 {
-    Material mAmbience = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material mAmbience = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material mMiddle = HomogeneousMaterial("Teflon", 2.900e-6, 6.019e-9);
     Material mSubstrate = HomogeneousMaterial("Substrate", 3.212e-6, 3.244e-8);
 
@@ -42,13 +42,13 @@ MultiLayer* TransformBoxBuilder::buildSample() const
     ParticleLayout layout;
     layout.addParticle(box);
 
-    Layer air_layer(mAmbience);
+    Layer vacuum_layer(mAmbience);
     Layer middle_layer(mMiddle, layer_thickness);
     middle_layer.addLayout(layout);
     Layer substrate(mSubstrate);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(middle_layer);
     multi_layer->addLayer(substrate);
     return multi_layer;
diff --git a/Core/StandardSamples/TwoDimLatticeBuilder.cpp b/Core/StandardSamples/TwoDimLatticeBuilder.cpp
index af0d483e68110b571e618ae003604c83f9612493..27ee942b3e98b869b546c60f23a0ae2463e1bca7 100644
--- a/Core/StandardSamples/TwoDimLatticeBuilder.cpp
+++ b/Core/StandardSamples/TwoDimLatticeBuilder.cpp
@@ -28,10 +28,10 @@
 MultiLayer* Basic2DLatticeBuilder::buildSample() const
 {
     Material particle_material = HomogeneousMaterial("Particle", 6e-4, 2e-8);
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material substrate_material = HomogeneousMaterial("Substrate", 6e-6, 2e-8);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer substrate_layer(substrate_material);
 
     std::unique_ptr<InterferenceFunction2DLattice> P_interference_function(
@@ -50,10 +50,10 @@ MultiLayer* Basic2DLatticeBuilder::buildSample() const
 
     particle_layout.setInterferenceFunction(*P_interference_function);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
@@ -64,10 +64,10 @@ MultiLayer* Basic2DLatticeBuilder::buildSample() const
 MultiLayer* SquareLatticeBuilder::buildSample() const
 {
     Material particle_material = HomogeneousMaterial("Particle", 6e-4, 2e-8);
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material substrate_material = HomogeneousMaterial("Substrate", 6e-6, 2e-8);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer substrate_layer(substrate_material);
 
     std::unique_ptr<InterferenceFunction2DLattice> P_interference_function{
@@ -84,10 +84,10 @@ MultiLayer* SquareLatticeBuilder::buildSample() const
 
     particle_layout.setInterferenceFunction(*P_interference_function);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
@@ -98,10 +98,10 @@ MultiLayer* SquareLatticeBuilder::buildSample() const
 MultiLayer* CenteredSquareLatticeBuilder::buildSample() const
 {
     Material particle_material = HomogeneousMaterial("Particle", 6e-4, 2e-8);
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material substrate_material = HomogeneousMaterial("Substrate", 6e-6, 2e-8);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer substrate_layer(substrate_material);
 
     InterferenceFunction2DLattice interference_function(10.0 * Units::nanometer,
@@ -123,10 +123,10 @@ MultiLayer* CenteredSquareLatticeBuilder::buildSample() const
     ParticleLayout particle_layout;
     particle_layout.addParticle(basis);
     particle_layout.setInterferenceFunction(interference_function);
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
@@ -137,10 +137,10 @@ MultiLayer* CenteredSquareLatticeBuilder::buildSample() const
 MultiLayer* RotatedSquareLatticeBuilder::buildSample() const
 {
     Material particle_material = HomogeneousMaterial("Particle", 6e-4, 2e-8);
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material substrate_material = HomogeneousMaterial("Substrate", 6e-6, 2e-8);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer substrate_layer(substrate_material);
 
     std::unique_ptr<InterferenceFunction2DLattice> P_interference_function{
@@ -158,10 +158,10 @@ MultiLayer* RotatedSquareLatticeBuilder::buildSample() const
     particle_layout.addParticle(p);
     particle_layout.setInterferenceFunction(*P_interference_function);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
@@ -172,10 +172,10 @@ MultiLayer* RotatedSquareLatticeBuilder::buildSample() const
 MultiLayer* FiniteSquareLatticeBuilder::buildSample() const
 {
     Material particle_material = HomogeneousMaterial("Particle", 6e-4, 2e-8);
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material substrate_material = HomogeneousMaterial("Substrate", 6e-6, 2e-8);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer substrate_layer(substrate_material);
 
     std::unique_ptr<InterferenceFunctionFinite2DLattice> P_interference_function{
@@ -190,10 +190,10 @@ MultiLayer* FiniteSquareLatticeBuilder::buildSample() const
 
     particle_layout.setInterferenceFunction(*P_interference_function);
 
-    air_layer.addLayout(particle_layout);
+    vacuum_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
@@ -203,10 +203,10 @@ MultiLayer* FiniteSquareLatticeBuilder::buildSample() const
 // -----------------------------------------------------------------------------
 MultiLayer* SuperLatticeBuilder::buildSample() const
 {
-    Material air_material = HomogeneousMaterial("Air", 0.0, 0.0);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0.0, 0.0);
     Material substrate_material = HomogeneousMaterial("Substrate", 6e-6, 2e-8);
 
-    Layer air_layer(air_material);
+    Layer vacuum_layer(vacuum_material);
     Layer substrate_layer(substrate_material);
 
     std::unique_ptr<InterferenceFunction2DSuperLattice> P_interference_function{
@@ -219,7 +219,7 @@ MultiLayer* SuperLatticeBuilder::buildSample() const
     // particles
     ParticleLayout particle_layout;
     FormFactorCylinder ff_cyl(5.0 * Units::nanometer, 10.0 * Units::nanometer);
-    Particle particle(air_material, ff_cyl);
+    Particle particle(vacuum_material, ff_cyl);
     particle_layout.addParticle(particle, 1.0, kvector_t(0.0, 0.0, -10.0 * Units::nanometer));
 
     particle_layout.setInterferenceFunction(*P_interference_function);
@@ -228,7 +228,7 @@ MultiLayer* SuperLatticeBuilder::buildSample() const
     substrate_layer.addLayout(particle_layout);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayer(substrate_layer);
     return multi_layer;
 }
diff --git a/Core/StandardSamples/TwoLayerRoughnessBuilder.cpp b/Core/StandardSamples/TwoLayerRoughnessBuilder.cpp
index 2db6e15c18c86239a6917dec009ad7f8eb6b96d8..8aa725574eca850f8cf024482b959d570c9cd41d 100644
--- a/Core/StandardSamples/TwoLayerRoughnessBuilder.cpp
+++ b/Core/StandardSamples/TwoLayerRoughnessBuilder.cpp
@@ -25,16 +25,16 @@ MultiLayer* TwoLayerRoughnessBuilder::buildSample() const
     const double m_hurst(0.3);
     const double m_lateralCorrLength(5.0 * Units::nanometer);
 
-    Material air_material = HomogeneousMaterial("Air", 0., 0.);
+    Material vacuum_material = HomogeneousMaterial("Vacuum", 0., 0.);
     Material substrate_material = HomogeneousMaterial("Substrate", 15e-6, 0.0);
 
-    Layer air_layer(air_material, 0);
+    Layer vacuum_layer(vacuum_material, 0);
     Layer substrate_layer(substrate_material, 0);
 
     LayerRoughness roughness(m_sigma, m_hurst, m_lateralCorrLength);
 
     MultiLayer* multi_layer = new MultiLayer();
-    multi_layer->addLayer(air_layer);
+    multi_layer->addLayer(vacuum_layer);
     multi_layer->addLayerWithTopRoughness(substrate_layer, roughness);
     return multi_layer;
 }