Reflective properties of materials

[speedy_thrills]

I have a white car with chrome door handles. The handles often get so hot on sunny days that I have to use a sleeve to open them if the car has been standing outside. However the surrounding area that's pained white, the panel itself, remains relatively cool.

Why then are the sun reflectors we use on the dashboards of cars a shiny finish rather than white? It seems white reflects more light.

[fasimew]

Because of material properties. Colour is just one thing. Look up mylar.

[Wayoftheflower]

Three factors at work that I can think of; Albedo, Coefficient of Heat Transfer and Heat Capacity.

Even if the albedo between white paint and chrome finish are similar (they'll both be quite high) the coefficient of heat transfer won't be. Metal being a really good conductor of heat and ceramics/plastics far less so, the paint will be more of an insulator. The heat capacity of a dense door handle compared to a thin body panel could be quite different (although the specific heat capacities may be similar).

TLDR, chromed metal door handle will be storing a lot of the sun's heat and more efficient at transfering it to your hand.

[Mr Whippy]

The metal will reflect a lot more of the suns heat too compared to the white paint.

But then the heat capacity and conductivity of the metal will be a lot higher than a plastic layer over metal.

[normalbloke]

This is why flocking was used on motorsport dashboards….Then along came vanta black( and it’s various non copywrighted alikes!)

[Penny Whistle]

normalbloke said:

This is why flocking was used on motorsport dashboards….Then along came vanta black( and it’s various non copywrighted alikes!)

And why bonnets were painted black on white competition cars (eg Triumph 2000s) in the 60s/70s.