Emissivity

The emissivity of a material (usually written ε or e) is the relative ability of its surface to emit energy by radiation. It is the ratio of energy radiated by a particular material to energy radiated by a black body at the same temperature. A true black body would have an ε = 1 while any real object would have ε < 1. Emissivity is a dimensionless quantity.

Emissivity table

Metal

Item	Smooth	Rough	corrosion
Aluminum	0.04	0.05	0.11~0.19
Brass	0.03	0.06 ~ 0.2	0.6
Copper	0.02	-	0.57
Gold	0.2 ~ 0.4	-	-
Iron	0.13 ~ 0.3	0.25~0.45	0.8~0.95
Lead	0.06~0.08	-	0.63
Nickel	0.04~0.09	-	0.37~0.48
Silver	0.02~0.4	-	-
Tin	0.04~0.07	-	-
Zinc	0.04~0.05	-	0.11
Yellow calcite	0.23	-	0.23

Nonmetal

Name of article	Emissivity
Asbestos	0.93~0.96
Brick	0.75~0.93
Carbon	0.93~0.97
Glass (soft)	0.94
Plaster	0.9
Marble	0.93
Oak	0.9
Paper	0.92~00.94
Lime	0.91
Ceramic	0.92~0.93
Crystal (coarse side)	0.93
Roofing paper	0.91
Rubber	0.86~0.95
Water	0.95~0.96

Paint Emissivity shown in rough figures depends on the surfaces.

Name of article	Emissivity
Black lacquer
White lacquer	0.8~0.95
Enamel	0.85~0.91
Oil paint	0.92~0.96
Aluminum paint	0.27~0.67
Varnish	0.89~0.93

Applications

Infrared rays	Industry	Deterioration diagnosis	Electricity, machinery, electronics, buildings and civil engineering
		Energy	Heat transfer, radiant heat, heat insulation property and test
		Non-destructive test	Wholesomeness evaluation and structural analysis
		Process monitoring	Quality control & monitoring
	Safety/Environment	Fire	Fire watch, firefighting & rescue and analysis of source
		Gas detection	Inspection of contamination and leak
		Quarantine	Airport inspection
	Medicine	Body diagnosis	Nervous system, musculoskeletal system, blood vascular system and metabolic disorders
	Medicine	Veterinary science	-
	Security	Military	Night guard and trace
	Security	Night watch	Night watch