Sounds like a myth to me.
I'd bet the small difference if anything the paint makes, would be lost again by the radiator having higher wind resistance.

In this case it is fluid contact not light so it is really dependant on the ability of the metal to absorb the heat and transfer that heat to the airflow going past. It could probably be purple and make no difference. Happy to be proved wrong though... cant see myself with a purple radiator

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Cheers
Alec
1275LS - July 78 - XNFAD18Y/102918

painting the radiator would insulate the aluminium, and make it keep more heat inside - you want to make sure the paint is heat conductive, engine paint would be OK, but I wouldn't do it...

the aluminium absorbs the heat from the water, black paint might help radiate more heat away from the radiator, but the difference would be minimal

You would definitely want to run coolant in these, not plain water- even so I'd be worried about corrosion long term.

I used to own an EA Falcon.... their 2 core POS alloy radiators clogged big time. A 3 core copper/brass taxi special one fixed it.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Was just wondering about the aluminium, because I used to have a radiator sales and repair business back in the 1980's,and we didn't see too many aluminium radiators back then,and all the radiators were spray painted black with some el cheapo paint we got from the radiator core suppliers, many of the cores even came already painted. The older car radiators are made of plated brass,with copper used for the cooling fins,with some of the larger industrial ones using copper tubes and even steel . Copper has better heat transfer properties than aluminium,but I guess aluminium is cheaper these days

I wonder if the paint was more about stopping radiators turning green than anything to do with radiating heat.

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

Yes I think that was the main reason ,to protect the metal from discolouring and corrosion which would reduce the heat transfer properties

The paint helps the heat transfer from the metal to the air.
I have one of Phil Irving's books where he lists the difference in heat loss between rough cast aluminium, polished aluminium and matt black painted aluminium.
It works even better if you paint the inside!

I remember an experiment on TV years ago, I think it may have been Julius Sumner Miller, where they painted one milk bottle black and another milk bottle white and filled them both with boiling water and then placed a thermometer in each one. The black bottle cooled down much quicker.

I believe it was Phil Irving who discovered that a thin coat of black on engine and gearboxes of motorbikes reduced oil temperature.
Black apparently both absorbs and radiates heat better then any other colour.
However, I would imagine some paints especially if applied thick would act more like an insulator.
All of the above was learn't via motorcycle magazines so it could be total........

You beat me to it Morris

Ahh why is it so

So back to my original querie , do you think it would help much with an aluminium radiator,a type which I haven't had much experince with

I think it would help, the easiest way to find out is to test one along the lines of the milk bottle test.

Hmm...... may have to buy 2 and paint one black

If it doesn't work stick it on ebay.