[TheForge] Aluminum annealing temp?

[Barking Crow]

I've been playing around with forging some trashpile aluminum rods about 3/8 
".  I forge it cold until I think it may break then stop and heat it with my 
little mapp gas torch until I think it might be annealed and then let it 
cool and start again.  Having fun punched and drifted a nice little hole.  I 
started out to make a wedge of aluminum to put in a collection of wedges of 
different size, shape, and material that I plan to give my daughter's 
boyfriend as a gift.  Then I was having fun and kept on playing for awhile. 
My question is how hot do I have to get the aluminum (a guess since I don't 
really know what the alloy is) before letting it cool?  I've been heating 
the piece until it is just barely red in the dark.  Is there a better way?

Thanks,  Jeff in Tallahassee