Removing part of layer not working

[ajackson]

I am fairly new to gimp (so forgive it this is a silly question) and am very frustrated with trying to erase or cut out part of a top layer only to reveal the background color (white) rather than the layer below. When I reduce the opacity of the top layer it reveals the one below. It is as if the background color is attached to the top layer!
I was in a gimp workshop this week and the instructor was using the windows version and it worked perfectly. Perhaps there is a mac trick I need to know about.
Thanks in advance for any help you can give me!

[virtualTune]

you would have to make a new layer with the colour you want below the layer you want to erase stuff on.

[David Wood]

It sounds like the layer doesn't have an alpha channel, that will prevent erasing and instead fill it with the background color. Right-click on the layer, and choose, 'add alpha channel'

[ajackson]

Well, yes, I have another layer. And that layer has an alpha channel.
I asked some PC gimp users and photoshop people to play with it and they threw up their hands. It makes no sense.
I just thought someone had run into this same problem.
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[David Wood]

Make sure the layer you want to erase from has the alpha channel.

[virtualTune]

well unfortunately there are currently no ac users active in this forum. sorry.

[ajackson]

THANK YOU, David! That was my problem. Apparently when I duplicated a layer, it did not have an alpha channel. I added it and it worked. Really appreciate the help.
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[virtualTune]

lol i am once again ignored! david, i will not post in this section of the forum anymore!