To do the job properly, you need to remove the whole piece of cloth from the frame. If it already came loose on its own in some spots, the glue is old and you should have no trouble pulling it loose without damaging the cloth. If you start, and simply pulling it off is looking a little 'iffy', then ge some Ronsonal lighter fluid (which is actually naphtha, used by dry cleaners) and squirt a line of it right through the cloth over where it attaches to the frame, It won't hurt the cloth or the plastic frame. Let it sit just a minute (it evaporates pretty fast) just long enough to soften the old glue, and gently pull off the cloth.
Clean all the old glue off the front of the frame. Don't try to clean it off the gloth, unless it's really dirty and has a lot of glue left on the back. In which case, you'll have to buy the gallon size of naphtha at Ace and literally rinse the entire cloth in a bowl of naththa OUTSIDE! Preferably with a good breeze blowing the fumes the other way!
Stretch the cloth front-side-down on a piece of clean plywood or some such, using push pins.
Don't stretch the hell out of it. Trace the frame on the plywood first so you know how much to stretch the grillcloth. Place the pushpins every 2 inches all around the cloth, as close to the edge of the cloth as possible. You're going to lay the frame back down on the cloth after you apply glue to it, so make sure the push pins will be about one inch + outside the frame tracing line all around (which will give you enough fabric to wrap around and glue the edge of the cloth the edge of the frame after the face glue dries.
Get a can of 3-M Spray Adhesive (Home Depot, Ace, Art Supply stores, etc. Lay the frame on the ground/floor on newspapers with the front surface, that you will glue to the cloth, facing up. Spray a liberal amount (but not running, maybe two or three light coats) straight down on the frame from about a foot away. As soon as it starts to get tacky (not more than thirty seconds) pick it up, quickly flip it over and place it down on top of the stretched fabric. You only get one shot! No shifting! So get it right the first time -- you might want to try a practice run before you apply glue to the frame ;-)
Once you've laid the frame on the fabric, GENTLY press the back of the frame all around to make sure the glue touches the back of the fabric. But gently! You don't want to squish any glue through the fabric!
Let it dry for a couple of hours where it's well ventilated, but not in the sun if the frame is plastic, because it might expand from the heat, and when it cools the cloth will sag.
I've done it this way for years on all kinds of frames. In the old days, when most frames were made of masonite, they just wrapped the cloth and stapled it to the back of the frame. I don't recommend trying to do the whole thing with hot glue; and if you just need to repair a single spot where the gloth has pulled loose, use a little contact cement.
The trick is getting the cloth evenly stratched before attaching it to the frame.
Good luck.
Neil
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