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Emissivity Values
Emissivity is a measure of a material’s radiating efficiency. An emissivity of 1.00 implies that the material is 100% efficient at radiating energy. An emissivity of 0.20 implies that the material radiates only 20% of that which it is capable of radiating.
Tables of emissivity values are only approximated values for real materials. A range of emissivity values is usually given for many materials whose emissivity can be affected by surface roughness or finish. Additionally, thin sheets of material such as plastics may be semi-transparent in the infrared and therefore have reduced emissivity.
To optimize the surface temperature measurement of a material:
- Avoid reflections by shielding the material from surrounding high temperature objects.
- For semi-transparent materials such as plastic film, assure that the background is uniform and lower in temperature than the material.
- Conduct the measurement perpendicular to the material’s surface whenever the emissivity is less than approximately 0.90. In all cases, do not exceed angles greater than 30 degrees from perpendicular.
Applicable for material temperatures from 0 to 250°C
Material |
Emissivity |
|
| Alumel | Unoxidized | 0.10 to 0.25 |
| Oxidized | 0.6 | |
| Aluminum | Polished | 0.10 to 0.05 |
| Oxidized | 0.10 to 0.40 | |
| Rough | 0.10 to 0.30 | |
| Anodized | 0.06 to 0.95 | |
| Aluminum Oxide | 0.4 | |
| Asbestos | 0.95 | |
| Asphalt | 0.90 to 1.00 | |
| Basalt | 0.7 | |
| Bismuth | 0.5 | |
| Brass | Polished | 0.05 |
| Oxidized | 0.50 to 0.60 | |
| Burnished | 0.3 | |
| Carbon | Unoxidized | 0.40 to 0.90 |
| Filament | 0.5 | |
| Soot | 0.50 to 0.95 | |
| Coke | 0.95 to 1.00 | |
| Graphite | 0.70 to 0.80 | |
| Carborundum | 0.80 to 0.90 | |
| Ceramic | 0.90 to 0.95 | |
| Clay | Fired | 0.95 |
| Concrete | 0.95 | |
| Chromel | Oxidized | 0.60 to 0.85 |
| Chromium | 0.1 | |
| Cobalt | 0.2 | |
| Columbium | Polished | 0.2 |
| Oxidized | 0.7 | |
| Copper | Polished | 0.1 |
| Oxidized | 0.20 to 0.80 | |
| Electrical terminal blocks | 0.6 | |
| Enamel | 0.9 | |
| Foods | 0.85 to 1.00 | |
| Formica | 0.95 | |
| Mullite | 0.80 to 0.85 | |
| Glass | Convex D | 0.8 |
| Nonex | 0.8 | |
| Plate | 0.90 to 0.95 | |
| Fused quartz | 0.75 | |
| "Pyrex, lead and soda" | 0.95 | |
| Gold | 0.05 | |
| Granite | Polished | 0.85 |
| Rough | 0.9 | |
| Natural | 0.95 | |
| Gravel | 0.90 to 0.95 | |
| Gypsum | 0.85 to 0.95 | |
| Haynes Alloy | 0.30 to 0.80 | |
| Human Skin | 0.99 | |
| Inconel | 0.35 to 0.80 | |
| Polished | 0.15 | |
| Oxidized | 0.70 to 0.95 | |
| Sandblasted | 0.30 to 0.66 | |
| Iron | Polished | 0.2 |
| Oxidized | 0.50 to 0.95 | |
| Rusted | 0.50 to 0.70 | |
| "Wrought, dull" | 0.9 | |
| Iron Oxide | 0.85 | |
| Lacquer | Colored on Al | 0.75 to 0.90 |
| Colored | 0.95 | |
| Clear on Al | 0.1 | |
| Clear on Cu | 0.65 | |
| Lead | Polished | 0.05 to 0.10 |
| Oxidized | 0.30 to 0.65 | |
| Rough | 0.4 | |
| Limestone | 0.95 to 1.00 | |
| Magnesium Oxide | 0.55 | |
| Molybdenum | Polished | 0.05 |
| Oxidized | 0.20 to 0.80 | |
| Monel | Oxidized | 0.45 to 0.85 |
| Nichrome | Clean | 0.65 |
| Oxidized | 0.60 to 0.85 | |
| Nickel | Polished | 0.1 |
| Oxidized | 0.20 to 0.95 | |
| Nickel Oxide | 0.6 | |
| Oil | Animal/vegetable | 0.95 to 1.00 |
| Mineral | 0.90 to 1.00 | |
| 25 microns thick | 0.25 | |
| 50 microns thick | 0.46 | |
| 125 microns thick | 0.7 | |
| Paint | Aluminum paint | 0.5 |
| Bronze paint | 0.8 | |
| Paint on metal | 0.60 to 0.90 | |
| Paint on plastic or wood | 0.80 to 0.95 | |
| Gold enamel | 0.4 | |
| Clear silicone | 0.65 to 0.80 | |
| Paper | 0.85 to 1.00 | |
| Plaster | 0.9 | |
| Plastic | 0.95 to 1.00 | |
| Platinum | 0.05 | |
| Polyester | 0.75 to 0.85 | |
| Polyethylene | 0.1 | |
| Quartz | 0.9 | |
| Roofing Paper | 0.9 | |
| Rubber | Hard, glossy | 0.95 |
| Soft, rough | 0.85 | |
| Sand | 0.80 to 0.90 | |
| Sandstone | 0.7 | |
| Shale | 0.7 | |
| Silica | Powder | 0.35 to 0.60 |
| Glazed | 0.85 | |
| Unglazed | 0.75 | |
| Silicon Carbide | 0.80 to 0.95 | |
| Silver | 0.05 | |
| Soil | Dry | 0.90 to 0.95 |
| Wet | 0.95 to 1.00 | |
| Slate | 0.70 to 0.80 | |
| Stainless Steel | Polished | 0.10 to 0.15 |
| Oxidized | 0.45 to 0.95 | |
| Steel | Unoxidized | 0.1 |
| Oxidized | 0.70 to 0.95 | |
| Cold Rolled | 0.70 to 0.90 | |
| Ground sheet | 0.40 to 0.60 | |
| Rough surface | 0.95 | |
| Tantalum | Unoxidized | 0.2 |
| Oxidized | 0.6 | |
| Textiles | Carpet | 0.85 to 1.00 |
| Close weave | 0.70 to 0.95 | |
| Cotton | 0.8 | |
| Leather | 0.95 to 1.00 | |
| Silk | 0.8 | |
| Died black | 0.98 | |
| Tin | Unoxidized | 0.05 to 0.10 |
| Tungsten | Unoxidized | 0.05 |
| Filament | 0.3 | |
| Water | Liquid | 0.90 to 0.95 |
| Ice | 0.95 to 1.00 | |
| Snow | 0.80 to 1.00 | |
| Wood | Planed | 0.80 to 0.95 |
| Sawdust | 0.75 | |
| Zinc | Polished | 0.05 |
| Oxidized | 0.1 | |
| Galvanized | 0.20 to 0.30 |
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