Very interesting, but open to misinterpretation due to the emissivity of the various parts.
What does that mean?
It means that the Infrared reading needs to be factored by the emmissivity of the surface.
For example the shiny chromed surfaces are not good at emitting heat, but dull black surfaces are.
I have posted the table below and you multiply by the coefficient to get close to the temperature.
Also you have to be careful about shiny objects as you might be reading a reflection of the sun (very hot) or the clear sky (very cold). Either way there are a lot of possible variations possible and as a certified IR technician I thought I would be a little bit of a picky reader.
When you see a big difference in parts the main real difference might be the emissivity of the surface.
Emissivity Table
Material Emissivity Value
Aluminium: anodised 0.77
Aluminium: polished 0.05
Asbestos: board 0.96
Asbestos: fabric 0.78
Asbestos: paper 0.93
Asbestos: slate 0.96
Brass: highly polished 0.03
Brass: oxidized 0.61
Brick: common .81-.86
Brick: common, red 0.93
Brick: facing, red 0.92
Brick: fireclay 0.75
Brick: masonry 0.94
Brick: red 0.90
Carbon: candle soot 0.95
Carbon: graphite, filed surface 0.98
Carbon: purified 0.80
Cement: 0.54
Charcoal: powder 0.96
Chipboard: untreated 0.90
Chromium: polished 0.10
Clay: fired 0.91
Concrete 0.92
Concrete: dry 0.95
Concrete: rough .92-.97
Copper: polished 0.05
Copper: oxidized 0.65
Enamel: lacquer 0.90
Fabric: Hessian, green 0.88
Fabric: Hessian, uncoloured 0.87
Fibreglass 0.75
Fibre board: porous, untreated 0.85
Fibre board: hard, untreated 0.85
Filler: white 0.88
Firebrick 0.68
Formica 0.94
Galvanized Pipe 0.46
Glass 0.92
Glass: chemical ware (partly transparent) 0.97
Glass: frosted 0.96
Glass: frosted 0.70
Glass: polished plate 0.94
Granite: natural surface 0.96
Graphite: powder 0.97
Gravel 0.28
Gypsum 0.08
Hardwood: across grain 0.82
Hardwood: along grain .68-.73
Ice 0.97
Iron: heavily rusted .91-.96
Lacquer: bakelite 0.93
Lacquer: dull black 0.97
Lampblack 0.96
Limestone: natural surface 0.96
Mortar 0.87
Mortar: dry 0.94
P.V.C. .91-.93
Paint: 3M, black velvet coating 9560 series optical black @1.00
Paint: aluminium 0.45
Paint, oil: average of 16 colours 0.94
Paint: oil, black, flat 0.94
Paint: oil, black, gloss 0.92
Paint: oil, grey, flat 0.97
Paint: oil, grey, gloss 0.94
Paint: oil, various colours 0.94
Paint: plastic, black 0.95
Paint: plastic, white 0.84
Paper: black 0.90
Paper: black, dull 0.94
Paper: black, shiny 0.90
Paper: cardboard box 0.81
Paper: green 0.85
Paper: red 0.76
Paper: white 0.68
Paper: white bond 0.93
Paper: yellow 0.72
Paper: tar 0.92
Pipes: glazed 0.83
Plaster .86-.90
Plaster: rough coat 0.91
Plasterboard: untreated 0.90
Plastic: acrylic, clear 0.94
Plastic: black 0.95
Plastic: white 0.84
Plastic paper: red 0.94
Plastic paper: white 0.84
Plexiglass: Perpex 0.86
Plywood .83-.98
Plywood: commercial, smooth finish, dry 0.82
Plywood: untreated 0.83
Polypropylene 0.97
Porcelain: glazed 0.92
Quartz 0.93
Redwood: wrought, untreated 0.83
Redwood: unwrought, untreated 0.84
Rubber 0.95
Rubber: stopper, black 0.97
Sand 0.90
Skin, human 0.98
Snow 0.80
Soil: dry 0.92
Soil: frozen 0.93
Soil: saturated with water 0.95
Stainless Steel 0.59
Stainless Plate 0.34
Steel: galvanized 0.28
Steel: rolled freshly 0.24
Styrofoam: insulation 0.60
Tape: electrical, insulating, black 0.97
Tape: masking 0.92
Tile: floor, asbestos 0.94
Tile: glazed 0.94
Tin: burnished 0.05
Tin: commercial tin-plated sheet iron 0.06
Varnish: flat 0.93
Wallpaper: slight pattern, light grey 0.85
Wallpaper: slight pattern, red 0.90
Water: 0.95
Water: distilled 0.95
Water: ice, smooth 0.96
Water: frost crystals 0.98
Water: snow 0.85
Wood: planed 0.90
Wood: panelling, light finish 0.87
Wood: spruce, polished, dry 0.86