diff --git a/src/lua/LuaElements.cpp b/src/lua/LuaElements.cpp
index b4023251e..4b215ed2e 100644
--- a/src/lua/LuaElements.cpp
+++ b/src/lua/LuaElements.cpp
@@ -856,7 +856,7 @@ void LuaElements::Open(lua_State *L)
 	LCONST(TYPE_GAS);
 	LCONST(TYPE_ENERGY);
 	LCONST(PROP_CONDUCTS);
-	LCONST(PROP_BLACK);
+	LCONST(PROP_PHOTPASS);
 	LCONST(PROP_NEUTPENETRATE);
 	LCONST(PROP_NEUTABSORB);
 	LCONST(PROP_NEUTPASS);
diff --git a/src/simulation/ElementDefs.h b/src/simulation/ElementDefs.h
index 285119e7d..3f16befde 100644
--- a/src/simulation/ElementDefs.h
+++ b/src/simulation/ElementDefs.h
@@ -17,7 +17,7 @@ constexpr auto TYPE_GAS           = UINT32_C(0x00000008);  //8 Gases (Includes p
 constexpr auto TYPE_ENERGY        = UINT32_C(0x00000010);  //16 Energy (Thunder, Light, Neutrons etc.)
 constexpr auto STATE_FLAGS        = UINT32_C(0x0000001F);
 constexpr auto PROP_CONDUCTS      = UINT32_C(0x00000020);  //32 Conducts electricity
-constexpr auto PROP_BLACK         = UINT32_C(0x00000040);  //64 Absorbs Photons (not currently implemented or used, a photwl attribute might be better)
+constexpr auto PROP_PHOTPASS      = UINT32_C(0x00000040);  //64 Photons pass through (may refract as in glass)
 constexpr auto PROP_NEUTPENETRATE = UINT32_C(0x00000080);  //128 Penetrated by neutrons
 constexpr auto PROP_NEUTABSORB    = UINT32_C(0x00000100);  //256 Absorbs neutrons, reflect is default
 constexpr auto PROP_NEUTPASS      = UINT32_C(0x00000200);  //512 Neutrons pass through, such as with glass
diff --git a/src/simulation/SimulationData.cpp b/src/simulation/SimulationData.cpp
index 4406f580e..cce75a52b 100644
--- a/src/simulation/SimulationData.cpp
+++ b/src/simulation/SimulationData.cpp
@@ -186,16 +186,14 @@ void SimulationData::init_can_move()
 		if (elements[movingType].Properties & TYPE_PART)
 			can_move[movingType][PT_SAWD] = 0;
 	}
-	//a list of lots of things PHOT can move through
-	// TODO: replace with property
+
 	for (destinationType = 0; destinationType < PT_NUM; destinationType++)
 	{
-		if (destinationType == PT_GLAS || destinationType == PT_PHOT || destinationType == PT_FILT || destinationType == PT_INVIS
-		 || destinationType == PT_CLNE || destinationType == PT_PCLN || destinationType == PT_BCLN || destinationType == PT_PBCN
-		 || destinationType == PT_WATR || destinationType == PT_DSTW || destinationType == PT_SLTW || destinationType == PT_GLOW
-		 || destinationType == PT_ISOZ || destinationType == PT_ISZS || destinationType == PT_QRTZ || destinationType == PT_PQRT
-		 || destinationType == PT_H2   || destinationType == PT_BGLA || destinationType == PT_C5 || destinationType == PT_RSST)
+		//a list of lots of things PHOT can move through
+		if (elements[destinationType].Properties & PROP_PHOTPASS)
 			can_move[PT_PHOT][destinationType] = 2;
+
+		//Things PROT and GRVT cannot move through
 		if (destinationType != PT_DMND && destinationType != PT_INSL && destinationType != PT_VOID && destinationType != PT_PVOD && destinationType != PT_VIBR && destinationType != PT_BVBR && destinationType != PT_PRTI && destinationType != PT_PRTO)
 		{
 			can_move[PT_PROT][destinationType] = 2;
diff --git a/src/simulation/elements/BCLN.cpp b/src/simulation/elements/BCLN.cpp
index 78be0805d..ae6f3f602 100644
--- a/src/simulation/elements/BCLN.cpp
+++ b/src/simulation/elements/BCLN.cpp
@@ -31,7 +31,7 @@ void Element::Element_BCLN()
 	HeatConduct = 251;
 	Description = "Breakable Clone.";
 
-	Properties = TYPE_SOLID | PROP_LIFE_DEC | PROP_LIFE_KILL_DEC | PROP_NOCTYPEDRAW;
+	Properties = TYPE_SOLID | PROP_PHOTPASS | PROP_LIFE_DEC | PROP_LIFE_KILL_DEC | PROP_NOCTYPEDRAW;
 	CarriesTypeIn = 1U << FIELD_CTYPE;
 
 	LowPressure = IPL;
diff --git a/src/simulation/elements/BGLA.cpp b/src/simulation/elements/BGLA.cpp
index 9b02e3da6..a2f5c81d8 100644
--- a/src/simulation/elements/BGLA.cpp
+++ b/src/simulation/elements/BGLA.cpp
@@ -29,7 +29,7 @@ void Element::Element_BGLA()
 	HeatConduct = 150;
 	Description = "Broken Glass, heavy particles formed when glass breaks under pressure. Meltable. Bagels.";
 
-	Properties = TYPE_PART | PROP_NEUTPASS | PROP_HOT_GLOW;
+	Properties = TYPE_PART | PROP_NEUTPASS | PROP_PHOTPASS | PROP_HOT_GLOW;
 
 	LowPressure = IPL;
 	LowPressureTransition = NT;
diff --git a/src/simulation/elements/C5.cpp b/src/simulation/elements/C5.cpp
index 963245bfc..5c8345193 100644
--- a/src/simulation/elements/C5.cpp
+++ b/src/simulation/elements/C5.cpp
@@ -32,7 +32,7 @@ void Element::Element_C5()
 	HeatConduct = 88;
 	Description = "Cold explosive, set off by anything cold.";
 
-	Properties = TYPE_SOLID | PROP_NEUTPENETRATE | PROP_LIFE_DEC;
+	Properties = TYPE_SOLID | PROP_NEUTPENETRATE | PROP_PHOTPASS | PROP_LIFE_DEC;
 
 	LowPressure = IPL;
 	LowPressureTransition = NT;
diff --git a/src/simulation/elements/CLNE.cpp b/src/simulation/elements/CLNE.cpp
index c3b910b8c..631e5d577 100644
--- a/src/simulation/elements/CLNE.cpp
+++ b/src/simulation/elements/CLNE.cpp
@@ -31,7 +31,7 @@ void Element::Element_CLNE()
 	HeatConduct = 251;
 	Description = "Clone. Duplicates any particles it touches.";
 
-	Properties = TYPE_SOLID | PROP_NOCTYPEDRAW;
+	Properties = TYPE_SOLID | PROP_PHOTPASS | PROP_NOCTYPEDRAW;
 	CarriesTypeIn = 1U << FIELD_CTYPE;
 
 	LowPressure = IPL;
diff --git a/src/simulation/elements/DSTW.cpp b/src/simulation/elements/DSTW.cpp
index 6d097c327..7d04bc3df 100644
--- a/src/simulation/elements/DSTW.cpp
+++ b/src/simulation/elements/DSTW.cpp
@@ -33,7 +33,7 @@ void Element::Element_DSTW()
 	LatentHeat = 7500;
 	Description = "Distilled water, does not conduct electricity.";
 
-	Properties = TYPE_LIQUID|PROP_NEUTPASS;
+	Properties = TYPE_LIQUID | PROP_NEUTPASS | PROP_PHOTPASS;
 
 	LowPressure = IPL;
 	LowPressureTransition = NT;
diff --git a/src/simulation/elements/FILT.cpp b/src/simulation/elements/FILT.cpp
index f471a40ff..880d58554 100644
--- a/src/simulation/elements/FILT.cpp
+++ b/src/simulation/elements/FILT.cpp
@@ -33,7 +33,7 @@ void Element::Element_FILT()
 	HeatConduct = 251;
 	Description = "Filter for photons, changes the color.";
 
-	Properties = TYPE_SOLID | PROP_NOAMBHEAT | PROP_LIFE_DEC;
+	Properties = TYPE_SOLID | PROP_PHOTPASS | PROP_NOAMBHEAT | PROP_LIFE_DEC;
 
 	LowPressure = IPL;
 	LowPressureTransition = NT;
diff --git a/src/simulation/elements/GLAS.cpp b/src/simulation/elements/GLAS.cpp
index 3034d94da..1cd5c7293 100644
--- a/src/simulation/elements/GLAS.cpp
+++ b/src/simulation/elements/GLAS.cpp
@@ -32,7 +32,7 @@ void Element::Element_GLAS()
 	HeatConduct = 150;
 	Description = "Glass. Meltable. Shatters under pressure, and refracts photons.";
 
-	Properties = TYPE_SOLID | PROP_NEUTPASS | PROP_HOT_GLOW | PROP_SPARKSETTLE;
+	Properties = TYPE_SOLID | PROP_NEUTPASS | PROP_PHOTPASS | PROP_HOT_GLOW | PROP_SPARKSETTLE;
 
 	LowPressure = IPL;
 	LowPressureTransition = NT;
diff --git a/src/simulation/elements/GLOW.cpp b/src/simulation/elements/GLOW.cpp
index c621e142d..69e16545a 100644
--- a/src/simulation/elements/GLOW.cpp
+++ b/src/simulation/elements/GLOW.cpp
@@ -33,7 +33,7 @@ void Element::Element_GLOW()
 	HeatConduct = 44;
 	Description = "Glow, Glows under pressure.";
 
-	Properties = TYPE_LIQUID | PROP_LIFE_DEC;
+	Properties = TYPE_LIQUID | PROP_PHOTPASS | PROP_LIFE_DEC;
 
 	LowPressure = IPL;
 	LowPressureTransition = NT;
diff --git a/src/simulation/elements/H2.cpp b/src/simulation/elements/H2.cpp
index c7cedc4c6..428a1242d 100644
--- a/src/simulation/elements/H2.cpp
+++ b/src/simulation/elements/H2.cpp
@@ -31,7 +31,7 @@ void Element::Element_H2()
 	HeatConduct = 251;
 	Description = "Hydrogen. Combusts with OXYG to make WATR. Undergoes fusion at high temperature and pressure.";
 
-	Properties = TYPE_GAS;
+	Properties = TYPE_GAS | PROP_PHOTPASS;
 
 	LowPressure = IPL;
 	LowPressureTransition = NT;
diff --git a/src/simulation/elements/INVIS.cpp b/src/simulation/elements/INVIS.cpp
index 8966ab860..e8efcde90 100644
--- a/src/simulation/elements/INVIS.cpp
+++ b/src/simulation/elements/INVIS.cpp
@@ -32,7 +32,7 @@ void Element::Element_INVIS()
 	HeatConduct = 164;
 	Description = "Invisible to particles while under pressure.";
 
-	Properties = TYPE_SOLID | PROP_NEUTPASS;
+	Properties = TYPE_SOLID | PROP_NEUTPASS | PROP_PHOTPASS;
 
 	LowPressure = IPL;
 	LowPressureTransition = NT;
diff --git a/src/simulation/elements/ISOZ.cpp b/src/simulation/elements/ISOZ.cpp
index 62c0cfc45..8c0faaad5 100644
--- a/src/simulation/elements/ISOZ.cpp
+++ b/src/simulation/elements/ISOZ.cpp
@@ -32,7 +32,7 @@ void Element::Element_ISOZ()
 	HeatConduct = 29;
 	Description = "Isotope-Z. Radioactive liquid, decays into photons when touching PHOT or under negative pressure.";
 
-	Properties = TYPE_LIQUID|PROP_NEUTPENETRATE;
+	Properties = TYPE_LIQUID | PROP_NEUTPENETRATE | PROP_PHOTPASS;
 
 	LowPressure = IPL;
 	LowPressureTransition = NT;
diff --git a/src/simulation/elements/ISZS.cpp b/src/simulation/elements/ISZS.cpp
index fc9146b18..813c3cbbc 100644
--- a/src/simulation/elements/ISZS.cpp
+++ b/src/simulation/elements/ISZS.cpp
@@ -32,7 +32,7 @@ void Element::Element_ISZS()
 	HeatConduct = 251;
 	Description = "Solid form of ISOZ, slowly decays into PHOT.";
 
-	Properties = TYPE_SOLID;
+	Properties = TYPE_SOLID | PROP_PHOTPASS;
 
 	LowPressure = IPL;
 	LowPressureTransition = NT;
diff --git a/src/simulation/elements/PBCN.cpp b/src/simulation/elements/PBCN.cpp
index 21ad6930e..2b7602c0a 100644
--- a/src/simulation/elements/PBCN.cpp
+++ b/src/simulation/elements/PBCN.cpp
@@ -33,7 +33,7 @@ void Element::Element_PBCN()
 	HeatConduct = 251;
 	Description = "Powered breakable clone.";
 
-	Properties = TYPE_SOLID | PROP_NOCTYPEDRAW;
+	Properties = TYPE_SOLID | PROP_PHOTPASS | PROP_NOCTYPEDRAW;
 	CarriesTypeIn = 1U << FIELD_CTYPE;
 
 	LowPressure = IPL;
diff --git a/src/simulation/elements/PCLN.cpp b/src/simulation/elements/PCLN.cpp
index c058379b7..2bf624875 100644
--- a/src/simulation/elements/PCLN.cpp
+++ b/src/simulation/elements/PCLN.cpp
@@ -33,7 +33,7 @@ void Element::Element_PCLN()
 	HeatConduct = 251;
 	Description = "Powered clone. When activated, duplicates any particles it touches.";
 
-	Properties = TYPE_SOLID | PROP_NOCTYPEDRAW;
+	Properties = TYPE_SOLID | PROP_PHOTPASS | PROP_NOCTYPEDRAW;
 	CarriesTypeIn = 1U << FIELD_CTYPE;
 
 	LowPressure = IPL;
diff --git a/src/simulation/elements/PHOT.cpp b/src/simulation/elements/PHOT.cpp
index 17cabaab1..5467563b6 100644
--- a/src/simulation/elements/PHOT.cpp
+++ b/src/simulation/elements/PHOT.cpp
@@ -36,7 +36,7 @@ void Element::Element_PHOT()
 	HeatConduct = 251;
 	Description = "Photons. Refracts through glass, scattered by quartz, and color-changed by different elements. Ignites flammable materials.";
 
-	Properties = TYPE_ENERGY|PROP_LIFE_DEC|PROP_LIFE_KILL_DEC;
+	Properties = TYPE_ENERGY | PROP_PHOTPASS | PROP_LIFE_DEC | PROP_LIFE_KILL_DEC;
 
 	LowPressure = IPL;
 	LowPressureTransition = NT;
diff --git a/src/simulation/elements/PQRT.cpp b/src/simulation/elements/PQRT.cpp
index ef3f8e106..268682cd8 100644
--- a/src/simulation/elements/PQRT.cpp
+++ b/src/simulation/elements/PQRT.cpp
@@ -32,7 +32,7 @@ void Element::Element_PQRT()
 	HeatConduct = 3;
 	Description = "Powdered quartz, broken form of QRTZ.";
 
-	Properties = TYPE_PART| PROP_HOT_GLOW;
+	Properties = TYPE_PART | PROP_PHOTPASS | PROP_HOT_GLOW;
 
 	LowPressure = IPL;
 	LowPressureTransition = NT;
diff --git a/src/simulation/elements/QRTZ.cpp b/src/simulation/elements/QRTZ.cpp
index a0c4987b6..1db2b1c89 100644
--- a/src/simulation/elements/QRTZ.cpp
+++ b/src/simulation/elements/QRTZ.cpp
@@ -32,7 +32,7 @@ void Element::Element_QRTZ()
 	HeatConduct = 3;
 	Description = "Quartz, breakable mineral. Conducts but becomes brittle at lower temperatures.";
 
-	Properties = TYPE_SOLID|PROP_HOT_GLOW|PROP_LIFE_DEC;
+	Properties = TYPE_SOLID | PROP_PHOTPASS | PROP_HOT_GLOW | PROP_LIFE_DEC;
 
 	LowPressure = IPL;
 	LowPressureTransition = NT;
diff --git a/src/simulation/elements/RSST.cpp b/src/simulation/elements/RSST.cpp
index d12f294f8..582e18873 100644
--- a/src/simulation/elements/RSST.cpp
+++ b/src/simulation/elements/RSST.cpp
@@ -32,7 +32,7 @@ void Element::Element_RSST()
 	HeatConduct = 55;
 	Description = "Resist. Solidifies on contact with photons, is destroyed by electrons and spark.";
 
-	Properties = TYPE_LIQUID|PROP_CONDUCTS|PROP_LIFE_DEC|PROP_NEUTPASS;
+	Properties = TYPE_LIQUID | PROP_CONDUCTS | PROP_LIFE_DEC | PROP_NEUTPASS | PROP_PHOTPASS;
 	CarriesTypeIn = (1U << FIELD_CTYPE) | (1U << FIELD_TMP);
 
 	LowPressure = IPL;
diff --git a/src/simulation/elements/SLTW.cpp b/src/simulation/elements/SLTW.cpp
index 95423b398..7492323a5 100644
--- a/src/simulation/elements/SLTW.cpp
+++ b/src/simulation/elements/SLTW.cpp
@@ -32,7 +32,7 @@ void Element::Element_SLTW()
 	LatentHeat = 7500;
 	Description = "Saltwater, conducts electricity, difficult to freeze.";
 
-	Properties = TYPE_LIQUID|PROP_CONDUCTS|PROP_LIFE_DEC|PROP_NEUTPENETRATE;
+	Properties = TYPE_LIQUID | PROP_CONDUCTS | PROP_LIFE_DEC | PROP_NEUTPENETRATE | PROP_PHOTPASS;
 
 	LowPressure = IPL;
 	LowPressureTransition = NT;
diff --git a/src/simulation/elements/WATR.cpp b/src/simulation/elements/WATR.cpp
index 849682903..c5e1da417 100644
--- a/src/simulation/elements/WATR.cpp
+++ b/src/simulation/elements/WATR.cpp
@@ -33,7 +33,7 @@ void Element::Element_WATR()
 	LatentHeat = 7500;
 	Description = "Water. Conducts electricity, freezes, and extinguishes fires.";
 
-	Properties = TYPE_LIQUID|PROP_CONDUCTS|PROP_LIFE_DEC|PROP_NEUTPASS;
+	Properties = TYPE_LIQUID | PROP_CONDUCTS | PROP_LIFE_DEC | PROP_NEUTPASS | PROP_PHOTPASS;
 
 	LowPressure = IPL;
 	LowPressureTransition = NT;