Best dark metal for solar absorbance.
What's the best metal for absorbing sunlight? ie, darkest.
It needs to be immersed in ethanol, which will dissolve pretty much any paint etc.
I've tried steel with some kind of enamel or anodised layer, but the eths started eating that too. Also whatever it was seemed to reduce the heat getting into the ethanol.
And are there ways of making metal darker, chemically or through heating?
I've been recommended getting something rusty and using a rust converter, which turns the oxidised layer into a phosphate, which is dark and might work well.
Also.. are there other characteristics I should be paying attention to in order to maximise the amount of heat transferred to the fluid, like conductivity, emissivity, etc?