I use alcohol as a solvent here because, as I said, I tend to have lots of it around. It's certainly safe enough, depending on how much of it you choose to drink, especially after it has had a lot of polyurethane dissolved in it.
Don't really know anything about acetone; have had very limited use of it in my work over the years, but never in quantities that would lead to overt exposure. I also use small quantities to dissolve Plexiglas to brew Bob Nunley's wood stabilizing formula.
Certainly, in a physiological sense, aldehydes and ketones are a group of chemicals that have some very un-nice members; but I think in most cases it's yet another case of "It ain't woth you fish, it's the way wot you fish it", and if you are careful to limit your exposure you are probably OK. (Peter McKean)
I've really struggled with varnish lately, trying to get a smooth finish. In my latest effort I wonder if the odorless mineral spirits (specs paint thinner) I've been using is part of my problem.
I have several clear poly tubes I use for dipping. I recently cleaned one of the spares out with the specs paint thinner, then used paint thinner from the same bottle to thin my current batch of varnish about 4-5% before dipping a rod that evening. The varnish was well mixed, and well strained through two different filters, so there should have been no contamination problems with the varnish mixture itself. When I checked the rod the next day, there were tiny specks everywhere in the varnish -- like minute dust particles. Needless to say, I was not a happy camper.
At the same time, I took a look at the spare dip tube I had cleaned. The mineral spirits left a white powdery residue that coated the inside of the clear tube. Now I'm wondering if I have some bad thinner? Thoughts??? (Harry Boyd)
I found the same darned thing when I used the odorless stuff last summer on a few rods. It ruined a gallon of poly spar!
Since using turpentine (expensive) I've not had the problem. (Joe West)
I use either naphtha or artist grade gum spirits of turpentine to thin varnish. The odorless mineral spirits has had some of the hydrocarbons removed. Good for cleanup, bad for thinning. (Rich Margiotta)
I wonder if the mineral spirits are attacking the plastic tube? I KNOW that acetone will eat some plastics. I think I'd try putting some of the thinner in a tube and leaving it for several hours (with a container under it in case it eats through.) Then see if the plastic seems affected at all (like softened perhaps.) (Neil Savage)
Good thought, but I don't think that's the case. I have a clear plastic pint bottle of Gillespie's brand low odor mineral spirits on my rod wrapping desk. I keep it there to clean brushes. It too has the white powder residue. Surely they wouldn't package their own product in something with which it might react?
More and more, thanks to several responses, I'm thinking the odorless minerals spirits themselves are the culprits. (Harry Boyd)
I keep a small jar of mineral spirits for dipping brushes to clean, also. After a while there is some white sediment in the bottom of the jar. I figured it was the varnish that was washed out of the brushes.
I used to wipe down blanks with a cloth and low odor spirits before dipping. Always seemed to have a few and sometimes, too many specks in the finish that I would have to buff out. I found a better grade of tack cloth that helped eliminate the specks. (David Dziadosz)
Is there a paint store near you? (Not a hardware that sells paint, but a specialty paint and wallpaper store?) They may have some ideas. There's a product called "Penetrol" that I've used with paint. There are several formulae but I don't know if there's one for varnish. It helps when the brush begins to drag. The one I used was the marine formula because I was using boat paint. (Neil Savage)
In my somewhat limited experience, the specs paint thinner appears to be pure poison to polyurethane spar. It'll precipitate white flakes almost immediately, and turn it to nasty goo over a longer period. It isn't quite so hard on traditional spars, but does seem to make them clot faster when used as a thinner (small bottle of MOW, and an identical bottle of MOW thinned with specs, both fairly full and tightly capped, had the thinned stuff clot into a solid mass over the course of a couple months on the shelf, while the unthinned stuff remained OK -- FWIW).
Maybe for cleanup, specs is OK, but for thinning, especially anything containing polyurethanes? No way! I've not experimented with thinning polyurethane spar with turpentine, but for traditional spars, it's good stuff. (Todd Enders)