I'm finishing up my seating modification. I glassed the seat tops, but lost track of my measurements, and the epoxy didn't cure! Not enpough hardener. I used the last of my 3/8 ply for the seats. My solution: Remove the cloth, wipe off the still wet goo, wash the pieces down with vinegar, then wipe with a wet rag. The result: almost dry, but very slight tackiness persists. I figure when I reapply the epoxy, the next bach of goo should provide enough hardener to deal with the resin left behind from my cleaning. Am I wrong? Help!
Dave
You're right! Just make sure you are working in the temp range for the epoxy. ;D
Once the resin and hardener touch each other, they no longer are the same chemicals, so a fresh batch of properly mixed epoxy will not do well over an improperly mixed batch. No amount of extra hardener or correctly proportioned epoxy will stick well.
The tacky surface needs to be removed with solvent as best as you can. Remove the bulk with vinegar and scraping with a putty knife. Then scrub the area with acetone. Scrub with a stiff brush (which will might melt in time from the acetone). Let this dry. You'll likely still have some tackiness, but greatly diminished. Next sand the tacky goo off with a fairly aggressive grit (40-60 grit).
The whole point of getting the bulk of the goo off is so you don't go through sand paper like chewing gum, which is what it'll seem like you're sanding.
Once roughly sanded, you're back where you started, so prep the surface again and be diligent about the mix. If you leave the tacky old goo as the base for the next batch, it will grip the surface with the tenacity of the messed up batch, not the new one. This is mostly because the surface pores of the wood, are filled with the bad batch (which is why it's tacky) and this will be the "grip" the new batch has on the wood, which isn't good.
Thanks, guys. The acetone got off the bulk of the tackiness. Some sanding with 80 grit paper got the rest. I went thru 4 random orbit sander papers to sand about 3 square feet of plywood! I just finished reglassing.
Dave
Something nobody seems to mention is that the combination of ACETONE & EPOXY is like opening a trap door in your skin to let the poison in...be very careful with epoxy and acetone!
Some times we have to assume folks will take reasonable precautions. I think it goes without saying, if you open a can of something and it smells like you wouldn't want it on your body, you probably would be best advised to not get it on your body, rub it in your hair, eyes or make peanut butter and . . . sandwiches with the stuff.
My standard recommendation is to download the major reformulator "users" guides. These have very clear and reasonable procedures and spell out the risks and necessary precautions.
would it be possible to sand down below it? or will it have seeped in too far?
Even if you vacuum bagged using hot resin, you'd eventually be able to sand down below it, though you may not have the room, such as on plywood, before a problem arises (running into a glue line for example). In most situations, you can "grind on through" and keep going.