I went to HD to look for flashing for solar absorbers. Someone at builditsolar.com recommended type 1100. I found 3 types: RV1425 VAAL 1425 : RV1225 VAGA 1225 : RV1010A VAAL 110

I guess it should be thin enough to bend in a jig and thick enough to transfer heat.

Here's a guy that specifies .0086 thickness. I have a thickness gauge so I'll take that in next time I go to HD.

Absorber Plate Construction

The guys over at the simply solar forum would be more than glad to help you. Its like a sister forum to builditsolar. A lot of the same guys.

Simply Solar

Jesse

I built a collector for my hot water system and used .018" aluminum I think. I don't know the grade of metal. It was Amerimax(?) flashing, painted. I probably overdid the silicone, but the 36 sf collector easily produces 21,000+ BTU on a 70F day in 4-5 hours of sun. Copper tube spacing was about 5.75" if I remember. I did not do the "coil in a tub" like many/most builtitsolar projects. Used a plate exchanger. Waiting to see how it holds up while exposed to city chlorine. Seems ok after 9 months.

Thanks, I did join that user group. I'm thinking the thicker metal will just conduct more heat to the pipes. If its too thick it would act as an insulator, I would guess. 21,000 BTUs for 36sf. Not too shabby.