openGL alpha blending with black

I am alpha blending and having success with white or any primary colors, but when I start to put some gray or black, it becomes more transparent even though the alpha value is all the way up. I need to know which alpha blanding function I should use to make it so that I can put all colors in there and have only the alpha value determine whether it is opaque or transparent. Thanks.


On my site, I’ve a example for loading a TGA with a mask.