Awhile back some of you might remember that I was having some issues with RR epoxy. Not enough for me to stop using the stuff, I’ve gone through probably well over a dozen gallons now, but enough to piss me off and make me question all of my methods. The problem was with hotcoats not entirely curing and feeling kind of rubbery, along with the alligator skin finish on the board. A sanding nightmare. I tried switching from measuring by volume to measuring with a scale. I had never had a problem in the past with measuring by volume, but I was so fed up I would try anything. Still didn’t resolve the issue. It kept happening to me on about half a dozen boards. Sanding is my least favorite part of this whole process to begin with, now it’s the step I dread the most. I tried Add F, I tried using the X-55 accelerator. Nothing worked. Yesterday I discovered the issue! So if anyone is having the same problem, or what to avoid this in the future, here is the solution!
My dad is a chemist. You’d think I would be a little more in tune with this subject but I’m not. The Add F was melting the plastic Solo cups I was using and mixing in with the resin, and screwing up the molecular bonding! When I first started and was measuring by volume in very expensive graduated cups from a boat store, everything worked out well. Then I started getting cheap and took clear plastic drinking cups and marked out volumes with water. The cups weren’t as chemically resistant as the boat store measuring cups. I went back to the boat store cups for my hotcoats and the last one cured hard as a rock. I still use the cheap Solo cups for my laminations, because it would be crazy expensive to use upwards of 6 cups for swirls, but I don’t use Add F on lams.
Thank you Rachel for the tips, I’ve always wondered about various inner coatings in paper cups and type of plastic of plastic cups and how they might react with the various chemicals. Auto body/paint supply stores have similar mixing products as the boat stores, for less fancy pricing. Auto paints use many very “hot” solvents that disolve everthing just like the board building chems.
I experienced the same exact thing, though I only noticed that the additive F seemed to be doing something with the cup, in my inexperience I didnt notice anything different in sanding.
I was going to bring it up before i did my next board, but you beat me to it. Thanks Rachel, good post!
Here is a pic where you can see on the back side of the cup the red showing through.[img_assist|nid=1041371|title=soloaddf|desc=|link=none|align=left|width=609|height=459]
I have absolutely no experience with epoxy, but if I have read correctly in the past, it seems that “additive F” contains a solvent known as xylene; this will act pretty much the same than styrene on certain plastics, namely polystyrene.
Some “cheap” cups are made of polystyrene. Those you should use (and they are not that much more expensive) are made of polypropylene or polyethylene. These two plastics will resist almost anything. I don’t know if there is such a thing as a marking of the material used under the bottom of those cups in the States? Here in France, if you look very closely, you will find two letters under each cup: PS, PE, or PP, respectively standing for Polystyrene, Polyethylene and Polypropylene.
You know, I’ve always used PE cups and have never heard of the problems you were having … never had them myself. Glad you figured it out. Sometimes the simplest things can cause the biggest problems.
I use the cups pictured for mixing, but the clear plastic versions rather than the red ones. Never had a bit of trouble.
For measuring, I use graduated urine specimen containers… ahem, “liberated” from my work. I re-use each one a bunch of times, however, by just cleaning them out with some scrap glass or some disposable shop rags. A lot of times I’ll leave the scrap glass/ shop rag stuffed in the container until I need to use it again.
I don’t have the luxury of using RR epoxy, however I’ve had similar problems with several generic epoxies without adding any solvents or anything. I’ve had epoxy which have melted holes in the thin white plastic cups, even holes in thicker clear plastic type though it takes longer. With paper cups the wax in the cups seem to sometimes dissolve and create a film on top of the epoxy. Using cocacola cups the red paint have dissolved, leaving nice red smudges whereever I touch the board… I sometimes use suringes to measure small amount of epoxy for ding repair, I notice that if I leave this laying around and try it the black rubber on the piston will leave black smudge on the inside of the cylinder.
I now use metered cups from a car paint shop, I guess they have so much solvent in the car paint they use that the cups must be very resistant to any solvent. Not too expensive either.
Awesome that you found the problem! I have used paper cups for mixing small amounts of colors for swirls and the such with RR with no issues if that helps.
i have been using painters cups from the local hardware store. at 97cents each they are getting to be a bit more expensive then originally thought. guess ill go out and get a few of these cheap cups when i dont need alot of resin.
You can reuse the painter’s cups. I use one per board. At a buck each it’s a no brainer. Just peel out the dry epoxy. You can use scrap cloth to wipe them dry when done glassing, then peel out the rest after it dries. They are even graduated for measuring.
I’ll either leave a stick in the cup, and pull out the epoxy popcicle… or set the cup upside down in the trash, then peel out the rest when cured.
I’m a hack, so I use the same cup over and over for laminating, because the tiny bits of debris don’t matter too much. But I use a new (or like new) one for hotcoating when clean-ness counts.
Hey Greg, Ive been saving some cups from yogurt I eat with intentions of using em for mixing my lam epoxy (I dont use add f in lam). The bottom of the cup says “PP” on it. Im assuming this is polypropylene, and will it be okay to use for this purpose? I wash em out with hot water, no soap or anything and wipe dry with a clean cloth. Would these even be okay for use with add F?
Im hoping that these cups will be reusable too, I dont think the epoxy will bond with em, but i am not a chemist. Anybody have an opinion?