Copying/pasting alpha channel

[jeremy.rutman]

Hi

I'd like to use a gradient as an alpha channel , so that for instance an image fades to transparent. 
I made a white->black radial gradient and did 'color->color to alpha' but now am stumped as to how to make this into the alpha channel for another image - I dont seem to be able to paste it as an alpha channel from 'Channels' which seemed like the most logical thing to do , and if I add this as a layer to another image and then merge down I lose the gradient alpha.
Maybe I need to use a mask?

[Ofnuts]

Yes, you would use layer masks. When you are editing masks, copy/paste operations apply to masks.

However, if you use masks, doing a black to white gradient on the mask makes the layer progressively opaque, and is likely the same thing as what you get with your white->black gradient followed by color-to-alpha.