Depending on the Grill Cloth material, you might try Carpet Cleaning Solution, diluted.
I took the small, gold speaker cloth from inside my DuMont RA-103 "Chatham", dipped it in this solution, and, within a minute, it had separated from the pressboard backing. I immediately patted the pressboard dry, and left the grillcloth in the solution.
You could see the nicotine leeching from the fabric...
After 15 minutes, I removed it, rinsed it gently with lukewarm water, and gently patted it dry. Try not to disturb the edges, or it will unravel. Then, I let it air dry. It didn't shrink.
I remounted it to the pressboard with spray mount, installed it with the Speaker in the Cabinet, and, it looks fab.
I detailed the opening speaker slots with Howard's before the install, so, it all looks great. The fresh Gold fabric peeking from the slots makes it all the worthwhile. Like resetting the Time Clock.
Details, details...
LJB
