[Twinge]

When using an Epson with Durabrite inks what shirt colors are considered light and what colors are dark aside from the obvious reds, navy blues, black.

When would I need to switch papers?

Personally, I only print on white and light ash; the "wax window" tends to show through on darker colors. However, you should still have decent luck with light yellow, natural, or very light blues. Your best bet is to try a sample (and wash it) and see if it fits your quality standards.

Incidentally, we actually had someone that really LIKED the paper showing through on a test light green shirt we did; said it made it look like the design was glowing or something. Most people won't though

 

[Twinge]

White and Light Gray/Ash is basically what I was thinking. Does the dark/opaque paper you use have a "wax window" outline on it? Can a black, navy or red be done with a professional finish?

I don't personally use opaque papers at all, as I do not like the feel and lower quality. Some people have decent luck with them though, and some customers/markets even like that rubbery feel.

Opaque papers will never have any sort of wax window as such - they transfer the entire paper, include the white background excess. you'll generally have to trim out the design completely to avoid transfering the 'white' over.

For doing a professional job on dark shirts with a heat press, I'd suggest looking at plastisol transfers or getting a vinyl cutter.