Bummer.
By the term “epoxy blank” I presume you mena EPS (expandalble polystyrene aka styrofoam (Dow trade name))?
Blanks are either EPS or Polyurethane “PU” for short.
Yes the bubbles are nasty, but because you used epoxy the cured glass will be easier to sand as Huskell mentioned. However, I would not just fill the area with resin in either way that Huskell suggests.
Don’t give up that easy.
Go ahead and use an exacto knife or similar to cut as much of the bubble and lifted area as possible You can use a razor, or Dremel type tool, or even just sand off the bubble with a coarse sandpaper block or grinder.
Fair in the edges as best you can next to the foam. No doubt the rest of the epoxied glass job is well cured now and you are going to have to scuff sand it before applying any mre epoxy or it will not stick properly. Depending upon the epoxy type your are using, read the label and see what it says about 2nd coats. If it says that you can add additional coats with 24 or 48 hours without sanding,and, you are in tht time frame, then consider yourself very fortunate. Or it may suggest that you do a wash over using denatured alcohol to acquire a new tackiness without requiring sanding. Again, if this is possible,count your lucky starts.
Chances are you will not be that lucky and you will need to put on some rubber gloves, grab a longsleeved shirt and tough it out scuff sanding the entire cloth layer. Might I suggest before you do that, buy some baby powder (talcum) and generously put it all over your forearms up to your elbows. Then don the longsleeve shirt and tape around the wrists if the shirt is loose fitting. What the baby powder does is temporarily fill your pores so the sande glass doesn’t.
Skuff sanding is NOT thorough sanding. You can use a block and some coarse sanding paper just to get some random scratches along the glass so the next coat has something to grab onto. Remove the bubbles best you can, fair in the edges some, then apply additional glass patches an inch or two past the cut out areas. You may want to baste the open bubble areas first than lay the cloth on top and squeegee down the repair area.
It sounds as though you have not done the other side of the board, so you may hae to scuff the repaired areas once they cure, or you may be able to flip the board and glass the other side then hotcoat it with still enough time to flip that over and hotcoat the repaired side. If too much time has gone by since repairing it, then scuff sand the glass patches so you can hotcoat allof that side at once.
Do not just put resin on the open bubble areas without glass.
Make sure your epoxy is very carefully measured per their ratios, and mix it very thoroughly.
To give your self more time, once mixed, pour it onto the entire surface of the side with a squeegee, plastic spreader quickly so it can soak into the cloth. If you leave the epoxy in the pot instead, it will heat up very quickly and you will have no work time. The idea is to get it distributed all over the surface in the least amount of time possible. Then start working your squeegee at a35 to 45 degree angle to the cloth starting from the center out. I use a pattern of center toward nose, center toward tail then so on so the cloth doesn’t shift all over the place. To quickly distribute the epoxy resin all over the cloth, I pour libera amounts of epoxy onto the board and bull doze it all over the surface without actual grabbing the glass. Then I go back and start doing the harder pressure from center out.
Long or wide overlaps are much more difficult for beginners to lap over. Pick what length seems comfortable to you and cut notches at nose and tail so you do not get wrinkles at those junctures. Try lapping them dry to see where they end up before ever getting the resin out.
Some people use the squeegee where others are more comfortable with a 2" or 3" chip brush. If your brush doesn’t seem stiff enough for the task, cut the bristles shorter until they feel firm. a 3" chip brush is cheap and the unfinished handles are just wood so you don’t have any color running off into your job.
Hope this gets you back on track.
