Is there any difference? Can I use rubbing alcohol to wipe down or thin epoxy? The reason I ask is I can get rubbing alcohol for next to nothing.
there is a difference: rubbing alcohol is about 70% ethanol or isopropanol , 30% water and stuff to make it too nasty to drink . Denatured alcohol is ~90% ethanol and ~10% methanol, plus that stuff to make it too nasty to drink. 30% water is a definite no-no; YMMV with denatured alcohol. It sounds like there are a lot of different recipes for DNA that add all sorts of different denaturants, if some of those denaturants aren’t very volatile it might explain why some people have good luck doing DNA wipes between layers of epoxy and others have fisheye problems.
Denatured has a definition in science dictionaries that may not agree with whats in various supplier’s cans. i went to the site of the supplier for Home Depot, forget the name, there was all kinds of wierd sounding chemicals listed on the MSDS sheet for the denatured, makes me wonder about toxidity issues, the home depot stuff has worked real good on a few epoxy projects so far.
I use 100% IPA alcohol, used for cleaning curcuit boards, I get in a L can from the computer shop, the owner always jokes that I must be making moonshine.
· universal electronic cleaning solvent · evaporates after use · for use on tape heads, disc drives, pcbs and other instruments and delicate components · safe on plastics · available in 400ml aerosol (re79l) and 1ltr can (re71n)…
dang.
Guess I can’t blame my epoxy hotcoat separation issues on denatured alc. contaminants - I bought mine from Home Depot in San Diego as well.
Another component to consider in the “alcohol wipedown” between epoxy coats is: The type of cloth or paper towel you are using. I don’t use cloth rags or towels, because of the possible chemical residue left from detergents after washing. This is just an instinct judgement on my part, not a scientific conclusion. BUT…My fish-eye problems have been small to none using only paper towels.
Don’t bunch them up and throw them in the garbage can, though. Best to leave them spread out flat on the ground until they dry before disgarding. I bunched up a stain-filled rag once and set it on the wooden shelf under my workbench. An hour later it was smoking, and had turned the wooden shelf to charcoal in the spot where it was laying. Lesson learned.
The last thing I want to hear is…WOOOOMP! Then see my shop on fire.
Doug
Isopropyl leaves a film behind, denatured doesn’t. In any case use Additive F and you don’t need to wipe down.
Hi Greg,
would you still recommend slow hardener to deal with some cases of fisheye?
Quote:
Occasionally the fast hardener will fisheye even with additive F. I wish I could tell you why but I don’t know. We feel it must be some kind of contamination in the air and this only happens very seldom. For some reason if you mix in some slow hardener or just use slow, if you see the problem occuring, it doesn’t do it. I’ve only had it happen twice and what we did was to squeegee the resin off and shoot another hot coat right away with slow. I wish I could tell you more. The other solution is to baby sit the hot coat (continue brushing until the resin thickens). A pain in the ass, but that works too. If this happened more often I could tell you why, but the fast hardener is over a year old and we’ve just seen it twice so …??? Slow has never done this.
If your having consistant issues with fisheyes then yes, slow is a bit better. If your using Add F in your laminate and hot coat and your using new brushes and your not wiping with anything and your still getting fisheyes, use slow hardener. But I never get fish eyes when I follow the rules.
I put down a cheater coat that went fine, waited about three hours, then put down a hotcoat that beaded up. I wiped off as much as I could, then waited and sanded it down. The second try on the hotcoat was much better.
details:
room temp stayed at about 75 - 80 degrees throughout. I tried to keep dust out, but in a garage on a dry breezy day, who am I kidding?
First prep: sanded deck and rails with 80 grit, vacuumed, wiped with DNA using blue shop towels.
Cheater coat: 2 cc add F per oz of fast hardener, ran it through a paint strainer, squeegeed on and went over it with a heat gun. There were a few bubbles, but not too noticeable. After 2 1/2 hrs the coat was firm but still tacky, I did the fill coat at 3 hrs. Didn’t touch the board at all between coats.
Fill coat: same mix, applied with a foam roller. It beaded up like water on a waxed car, rolling back over it didn’t help. Squeegeeing it off improved the coverage a bit but there were still big uncovered areas.
Second surface prep: Sanded with 80 grit until it was just about level again, but I didn’t get all of the depressions completely flush. Any dips that were still shiny were scuffed up with a scotchbrite pad. Vacuumed off, but no DNA wipe.
Second fill coat: same mix, applied with a new brush. Much better - still a few fish eyes, but I was able to brush almost all of them out before the resin set.
Did I wait too long between coats?
Your working too hard to try to make everything perfect and in the mean time your adding a bunch of potential problems. After the laminate you sand lightly mostly getting the laps flat and all the high spots down. Wipe the excess sanding dust off with a white Tshirt or a paper towel. Tape off around the perimeter and sqeegee your cheater on if needed. Let that tack up and then brush on your hot coat. I only use 1 cc Add F per ounce of hardener. That’s adaquate and using more may give you problems. I only use more if it’s extremely hot (which it never is in SD) or on a gloss. Rolling on the hot coat may have made it too thin which could have made it bead. Use a brush, a new one, a 3" chip brush. If you push the bristles into the sticky side of a piece of tape before you hot coat you can remove loose hairs. If you don’t the brush may shed a bit but unless the board is colored you probably wouldn’t see them anyway. Brush on a normal hot coat, it should flow perfectly. This is the way I do it … simple. I never get fish eyes.