I like to dilute poly 50-50 with mineral spirits on the first coat, and subsequent coats diluted 2-1 or even 3-1. It makes the finish go on smoother and without bubbles or wrinkles. Anyone else like to dilute finish with mineral spirits, and if so, what is your ratio?
Regards,
Boris
Boris
“Sir, I may be drunk, but you’re crazy, and I’ll be sober tomorrow” — WC Fields, “Its a Gift” 1927
Replies
Boris,
Yes, diluting is good. Any ratio that works. Of course, it takes longer to gel the film thickness that undiluted mixtures gives. But diluting makes application almost fool proof.
BTW,
I thought it was:
"Madam, I may be drunk, but you are ugly. Tomorrow I shall be sober, but you will still be ugly.'
I thought it was:
"Madam, I may be drunk, but you are ugly. Tomorrow I shall be sober, but you will still be ugly.'
Two different quotes--yours is by Winston Churchill.Gretchen
I always thin my first couple of coats by 50%. Last coats thinned about 25% +/-. Why? Well, I think thinning the first coats gives you better penetration and fiber locking. In other words, using it as a sanding sealer. And on the last coats it gives better flow control.
PlaneWood by Mike_in_KatyPlaneWood
Gretchen,
Thanks! And I'll bet he didn't originate it, neither.
R
No, I think he did. It was a pretty well known incident--when he was considerably younger as I recall.Gretchen
Rich,It was said to be an encounter with a Labour MP, called Bessie Braddock, in a corridor in the Parliament Building and said in reply to her accusing "Winston, you're drunk!"Probably an apocryphal story since Bessie was a formidable woman and I can't imagine Churchill still standing up after that reply.
Ian,
In all probabilty, apocryphal, yes.
BTW, the first time I heard the word, "apocryphal" was from my wife, who must have learned it that morning as her "word of the day." She must have practiced using it in a sentence all day long.
When she spoke it, it was one of those words that I knew I should know, but didn't. I waited a few seconds and asked what it meant. She replied with a perfectly straight face, "Oh, you know - 'ersatz' "
I don't know how she pulled off the dead pan look. We stood there for a few seconds looking at each other before we both collapsed in convulsions of laughter.
What would life be without a good thesaurus?
R
Da, comrade. Especially the poly. Too thick in the can. I mix finish like I cook, to taste. When it feels right, it flows right. I don't know if I have to use mineral spirits to reply here, but I prefer naptha for varnishes, and if it's compatible, I prefer lacquer thinner over just about everything else since once it's down it flashes off fast enough to get things curing like they should. I know, that's absurdly finicky. I probably go more like 1 to 5 with polys, but Behlen's Rockhard is so thick in the can that's more of a 50/50 proposition. I guess it's just as well. For $18 a quart you better get some stretch out of it. Good stuff though.
Most urethanes are tihinned with mineral spirits. Can I still use lacquer thinner as a thinning agent?
That would be nice it would really cure fast.
Regards,
Boris
"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1927
No, lacquer thinner is not a thinner for oil based finishes. You can use naphtha which will become dry to the touch faster but varnish still needs the same amount of time to fully cure.
You are correct. Most are. I haven't tried lacquer thinner on poly recent enough for the wires upstairs to recall. I use it on a wide variety of oil based products and its something of a lottery whether it works or not. You don't always know exactly what went in to a particular brand. Easy way to test, though, put a little of the finish in question in a dixie cup and put the thinner in and stir. If it mixes, that's good sign #1. Then test it on a scrap and let it cure. If it looks crackled or scaly or . . . then go back to the naptha. My comment on the lacquer thinner has mostly pertained to oil paints, and there I haven't found one yet that doesn't work with it. (That doesn't mean they don't exist, but everything Sherwin sells is compatible) Most of the time I use oil, I'm pushing it through a pot and it needs the thinning just for spraying consistancy. But this does not accelerate cure time per se. The finish does dry to tack faster rather as a byproduct - you're putting on a thinner coat, and the thinner used flashes quickly, which lets the product start drying. If the can says 2 days to cure fully, that doesn't change. The only advantage of quicker "dry to the touch" is reapplication, so when you're painting vertical surfaces you can get done spraying faster without the runs and sags. Another solvent useful if you really want to worry about sags is acetone, but it's about as "hot" as you can get (and therefore does not react well with a multitude of finishes) and as you are probably aware, stinks to high heaven when used in any quantity. So did that clarify or confuse more?
No problem thinning oil based poly varnish. In fact, a 50/50 thinning with mineral spirits/naphtha is the same as "wiping varnish".
The only two things to keep in mind is that a varnish containing flattening agents should not be thinned beyond what it calls for on the can. The flattening agents will not stay in suspension and white streaky areas may result. If you want a "satin" finish, use brushed on, full strength coating of satin finish as your final coat. The second thing to remember is by thinning the varnish you will need to apply more coats to get the same film thickness and protection.
While I use homebrewed wiping varnish most of the time these days, I have brushed miles of varnish in marine applications. A slight thinning (5-10%) generally allows the finish to flow out better but the primary way to remove bubbles is to first apply the varnish by flowing it on--don't do a lot of brushing back and forth--and then "tip" it off using an almost dry brush and just use long strokes just barely letting the bristle tips touch the surface. The "tipping off" breaks up all the bubbles and smoothes the finish.
Howie,
How do you prevent puddling with that last full strength poly coating?
Thanks, Darrell
"Sir, My poly has bubbles and I'm not even drunk. Tomorrow the poly will dry and it will still have bubbles."
Not sure what you mean by "puddling." I have never heard the expression before. Good brushing technique will get the coating on properly. Like anything in woodworking, finishing is something that must be practised and learned.
I think applying full strength poly is very dificult, and yes it puddles for me; blobs of extra poly in places where it ought not to be. In order to achieve more flowing and self leveling, I dilute it. I think the strongest concentration I have been able to get away with is about a 2-1 ratio (30% cut), but that depends on the type of poly.
Regards,
Boris
"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1927
This forum post is now archived. Commenting has been disabled