I have been attempting to varnish some closet shelves for the past two weeks and have been running into problem after problem. I know these problems are likely result of my inexperience, however I’m looking for any suggestions that may be helpful to me at this point.
I first applied Minwax prestain wood conditioner and then Minwax oil based wood stain (golden pecan). This went on well and everything seemed to be going good until I attempted to varnish the project. I am brushing on Minwax fast-drying polyurethane and sanding lightly between coats with 320 grit. My problems started immediately after the first coat because a large amount of bubbles formed in the polyurethane as it dried. After sanding and applying a second coat these bubbles were no longer noticeable and the second coat did not produce the same bubbles. The problem then was that when the coat dried you could see my brush strokes in the finish, almost as if I did not thin the poly enough (I had been thinning it about 2.5 to 1 with mineral spirits). Seeing this, on my third coat I attempted to thin the poly more (about 1.5 to 1). This was noticeably thinner, and went on well. However, when it dried the finish looked fine straight on, but when looking at it from an angle you could see what I can best describe as a film on the surface. It reminds me of what it would look like if you looked at the project through the smoke of a fire (wavy) and the film appears to be white in color. Like I said though, you cannot see it when looking straight on. I would like to only put one more coat on the project before calling it quits so I’m looking for suggestions on how to avoid the brush strokes and the wavy film. I should mention that the project is made from maple plywood with a hardwood maple strip on the edges.
Any suggestions on what I may be doing wrong would be appreciated and please don’t hold back. I realize I may be making some stupid mistakes.
Replies
I use Minwax fast drying polyurethane and I use it right out of the can and using a good quality china bristle brush I do not get any brush marks. However there is always some dust nibs on the finished surface ao for my last coat I first sand with 800 grit paper then apply a coat of Minwax Wipe on Poly. I never tried thinning it as it went on so well out of the can.
Stop thinning the Minwax poly.
Beat it to fit / Paint it to match
DanielB ,just thought I would point out that poly is not varnish.
it is actually a good idea to cut only your seal(first) coat, and no more then 5%,using free flowing paint thinner( most stores sell it as odorless thinner) though it is not necessary to thin it, I find it gives a more even first coat. also make sure you do not cheap out on your brush,make sure it is a true bristle brush.
Now I would power sand with 220 grit dri-lube paper removing your entire last coat,and then apply one finial coat with NO CUT!!
a little note; all of these (fast drying)poly's are pre cut,therefore they spray better then they brush.yet they flow nice with a good brush as well.
Dan
Single part consumer grade poly is certainly varnish. Minwax is pretty skimpy with it's information, but this is most likely an vinyl-alkyd varnish with some polyurethane resin. And, it comes with a fairly high solids content, so like all varnishes I know it does need some thinning for use. Bubbles generally mean that the varnish is too thick for them to pop before the varnish begins to set. This can be a particular problem with such fast drying varnishes. I'd thin about 10% with paint thinner, and certainly agree with the suggestion to use a good quality natural bristle brush.
None of these oil based varnishes, even these fast dry varieties, dry fast enough to be comfortably sprayed without specialized booth to remove overspray. Certainly Minwax's target market does not include spray finishers.
Manufacturers of oil based finishes always say not to thin their products. It largely has to do with VOC regulations. If the label said the user should thin, then that wouild be about the same as having the volitile organic compounds already in the can. It's possible to brush on syrup as varnish, but much easier if it flows more readily.
Edited 4/16/2009 3:47 pm ET by SteveSchoene
OK.good thing I do have a spray booth. But I have sprayed many 30' long bars I have built with a simple fan set up/and the back bar as well/80 or so table tops ,with zero over spray problems. Mybe you can not spray it comfortably?But I know many who can.
the properties of poly and varnish are different ,was my point .my objective is never to insult . How about you?
Sure it can be sprayed, but generally there are lots of products other than consumer grade varnish that I would want to be spraying, though the very fast drying varieties do come closest. And, for on-site spraying you can likely get away with less serious ventilation than would be necessary for things like 2-k polyurethane (which deserves the name poly) and other finishes better sprayed than brushed.
There are a wide range of polyurethane products, but the single part oil bsed products sold in consumer markets are basically alkyd varnishes with a bit of polyurethane added for marketing purposes and some added abrasion. But in general these are all varnishes with very similar properties. I would consider the vinyl-modification in the very fast drying products more significant than the polyurethane. I just think most finishers would be better off considering these products as all being variations on one theme, rather than special products. This is particularly true for finishing furniture, where I seldom see any reason to use a polyurethane modified varnish as opposed to a alkyd or phenolic varnish without the polyurethane modification.
Edited 4/16/2009 4:34 pm ET by SteveSchoene
I my self do not like varnish on furiture.how ever if it suites the clients needs I will use it. I am not by any means alone on this . I was trained by old timers(now in there late 80's) who would varnish every thing.
I personally do not use the fast dry stuff much ,mostly true poly and seldom in my booth/that is for lacquer mostly. the only things I varnish, are cars (wood only)and boats of which I have done a bunch of both.always got paid and pride myself on having no call backs due to faulty finishing.
any how, I hope some how all this helps the poster correct there finish issue!?
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