I love oil-based Polyurethane. I love the amber color it creates three years down the line. I love its durability.
What I dont love is the consistent problem I am having with applying it with a brush. If you thin it down it runs quickly. If you leave it thick it runs slowly. The only way I have found to keep it from running it by nearly dry-brushing it on. With a raking light, you can see the “wet” being applied. But it is such a thin coat that way. It would take 8 coats to make a difference.
I have a cousin in dallas who sprays it with a cup sprayer. I am too chicken-%# to try that. The runs would being uncontrollable,..so I think.
What is the way you do it to stop it from running. I succeeded one time and managed to get a smooth, thick buildup. But it was years ago and I never knew how I did it. If I rememeber right, my last coat was VERY thin,..but I am not sure.
Any help will be appreciated.
thank MJB
Replies
I have successfully sprayed Minwax oil-based polyurethane (that's not the exact name they give their product) as well as an exterior varathane using my Lemmer HVLP compressor-driven gun. It driea much more quickly than when I brush it on, and leaves no brush marks, and didn't show any sags nor runs.
I have, however, ceased using oil-based urethanes and now use water-based finishes almost exclusively. Not only can I safely spray them in my basement shop, but the clean-up is so much easier. Moreso, my wife, who used to get headaches whenever I'd use oil-based finishes, tells me that she cannot smell the water-based products. I do, however, have a portable spray booth that I set up in my workshop, aimed towards a window fan that exhausts virtually all of the fumes (I open another window on the other side of my shop, to ensure that I'm not creating problems with the furnace and hot-water heater's flue exhaust). I should mention that I use a high-quality face mask, outfitted with the proper filters.
If you'd like more information on my home built portable spray booth, let me know and I'll send you a few photos of it. It was very easy to build. Good luck with your finishing.
Croc
Please send photos.
Jeff
Yo cutawooda,
nice screen name, I like it. But seriously, I hope that what I have to offer willhelp you. You didn't mention anything about thinning the poly that you are using so I will assume that you are trying to use it straight from the can. When poly is that thick it is nearly impossible to apply in a thin enough film that won't run. Try thinning about 15% with naptha. At this consistency the poly will flow much better and level nicely, i.e. no brush marks. I have yet to get the perfect finish by brush alone so after 2 brush coats I will lightly scuff again and then do 1 coat with a wipe-on poly. This leaves a perfect finish that is smoother than a baby's butt. I would highly recomend Old Masters Wiping Varnish if you can locate it. I get mine at the local True Value hardware store. It is a gelled varnish, just reach into the can with your rag and grab a little to apply. The other wiping polys that I have tried were liquid that had to poured(?) into the rag to apply, a slower process. Wish you the best of luck, Let me know what you think.
Cuta
I use Poly all the time on cabinets.
I hate brushing, so I wipe it on.
I use McClusky's Spar Varnish (I happen to like it, no other reason) that I simply mix 50/50 and and wipe a thin coat on with a rag (clean white cotton).
Usually 3 or 4 coats do the trick.
Jeff
PS: More coats tend to give a shiny finish, less natural looking. Thats why I stop at 4 coats.
Edited 1/24/2006 9:06 am ET by Sardog
Edited 1/24/2006 9:06 am ET by Sardog
your cousin is right, spraying yields a superior finish to brushing, all labor time being equal.
Still, if you are seeking the best possible finish by brush, buy a badger hair brush-not cheap- about 85-100$. Thin as suggested with naptha. You could also use a product called Floetrol to increase levelling. Each coat requires fine sanding or electric sanding with with automotive polishing compound.
ok,..I have always been convinced of spraying. I have a binks cup sprayer. What is the mix for spraying poly. Be specific please.
thanks
ok but let me say first that I prefer lacquer for all furniture-it offers depth, superquick drying and to me, a better luster.
With poly, thin the first coat 15-20% with naptha.No more than 1 to 5 ratio. Reduce the use of naptha each coat till you spray poly full strength on the third coat.If you're overly concerned about amounts, there is also the Zinnser cup method(maybe google it?), basically it's just timing drips into a cup.
For whatever it's worth, here's how I brush poly -- works for me, no problems, including vertical surfaces. I do sand lightly between coats and tack with mineral spirits. I use a high quality brush and dip the brush in mineral spirits and shake out excess before starting. Working quickly I brush on a reasonably generous amount of poly to ensure good coverage over the entire piece and then -- I guess this is where the action is -- using light brush strokes in the direction of the grain, go over the entire piece again, even several times as needed, removing the excess. Do not re-dip the brush when doing this and when the brush gets loaded, remove the excess poly from the brush. It doesn't take a lot of practice to get the initial brushing on wet enough so that when going back over the piece and rebrushing, it is all still nicely wet, but not too wet (don't encourage runs, but don't worry too much if you get some runs during the initial brushing). On the "re-brush," a good brush picks up the excess poly and leaves a very smooth finish. To me, looks as good as sprayed (smooth with very, very slight orange peel -- same as sprayed to my eye). If you want a surface literally like glass, a little wet sanding and buffing will get you there.
Anyway, best of luck.
Because the poly is generally thinned out so much, how many coats do you apply before wet sanding and buffing? I am doing a table top now and am using a wipe on poly for its durability. The only experience I have with wet sanding and buffing is with spray on lacquer. I don't want to sand through the coats of the poly. Thanks in advance.
Hello:
I usually apply 4 or 5 coats of poly (I apply it unthinned though). When you wet sand, just sand enough to flatten any orange peel and no more. It doesn't take much off of the finish depth to make it flat as float glass. I dry sand between each coat of poly (320 dry paper), and even paper that rough doesn't get through a coat (I'm careful with it, but even 320 doesn't take much care). Buffing takes even less off of the finish (of course). Anyway, send pics when you have it done; would like to see it.
I'm in the middle of finishing up a large oak panel for a powder room ceiling. Sanded it for about 4 hours to get the surface I wanted, and have it stained and the first coat of poly on it. Four more coats, a little wet sand, buff, and it almost won't look like a piece of wood anymore (too smooth). On the other hand, I have done some work where I left a little bit of the grain showing through the finish so you can tell it actually is real wood, but I always felt it gave a piece too much of a "home made" look, so I'm back to the smooth as glass approach. Some like it; some don't.
Best of luck.
thanks for the tip, I will work on it. I wasn't sure how many coats could be built up with poly. The lacquer I use usually has a max of 3 to 4 before you risk the 1st coat cracking during the shrinking period.
I will forward a pic when done.
You're welcome. I'm sure there are better ways, but the descriptions I gave are how I do it and I like the results, the people who end up with my pieces like the results, so it works for me (one favorite piece is a smallish cabinette that I did for myself and kept -- when my girlfriend invites her friends over many take notice of it and ask "where did you buy that, I love it," etc. Would be great for business if only my girlfriend's friends would be willing to pay what I charge ;-) I don't "specialize" in furniture making, but I do view my finish carpentry in many ways as like making parts of a huge piece of furniture called a house, where many of those parts are basically fine "furniture" (like the built-ins and detailed trim items like mantles, coffered ceilings, paneled walls, etc.) and with the right mindset, the results show. I always learn a lot from all the woodworkers here, with the most important thing being that certain mindset of doing the best possible job for oneself, even if the client doesn't always fully appreciate/comprehend or even care what goes into doing that.
On the cracking issue, never thought to mention that I use the Minwax fast dry poly (don't know if that makes a difference, but that's what I use). Never had a problem with cracking. Only problem I ever had was when a helper got way overzealous on a horizontal piece with a mess of a thick coat and the finish got real "gummy" in a couple of places. No way it would crack, and even with that mess, it didn't alligator and it was easy enough to fix once it dried enough to be sandable. Maybe it is the Minwax that saves my butt; don't know for sure.
Upshot of all this -- if I could presume to make a recommendation -- it would be to experiment. Try my way if you think it makes sense for you; try ways suggested by others; experiment to improve even on those ways; use what works best for you.
Anyway, I must stop rambling -- must be reluctant to start work this am for some reason. Glad to be of help if I have helped and I again wish you all the best.
Sort of like a French applied... you can see the "wet" being applied
I think that is the best what ever method you use.. Brush OR Spray!
smooth, thick buildup.
Thick gets ya in trouble ALL the time!
This forum post is now archived. Commenting has been disabled