I have just completed building a desk out of Oak Veneer Plywood with solid oak doors, faceframe, etc., and have applied a stain. I know nothing about finishing, but I would like to use an oil based polyurethane finish as the desk top will receive heavy use. Question: what/how is the best/easiest way to apply a couple coats of poly without getting all of the “nibs” that I usually end up with? I have always brushed it on in the past on other projects but I do have an air compressor and spray gun, which I have used for other finishes.
Your recommendations would be appreciated.
Don
Replies
I've usually sprayed it on, at least on anything that can't be brushed on in 5 minutes. Add maybe 20% good quality paint thinner. Very light spray on the vertical surfaces and have a good quality paint brush ready.
I also have rubbed it in with the palms of my hands. Then a rag slightly damp in thinner to clean it up. 3 or 4 coats then a good buffing makes a nice finish for a table top.
PlaneWood by Mike_in_Katy (maker of fine sawdust!)
PlaneWood
I brush or use a rag, and usually thin the first & last coats-
I usually brush on a wet coat of wipe on poly (I use minwax because I can get it up in town; I don't know which wipe on poly is "best"). I let it set for 10 or 15 minutes, keeping it wet, then rag it off. I usually use paper towels, then remove the lint with a small cotton rag. The idea is to impregnate the wood, as much as possible, with finish that will later harden.
After a day or two, I lightly sand with 320 or 400 and then follow the wipe on poly instructions for 3 (vertical, non-stressed surfaces) to 6 (horizontal and highly stressed surfaces) coats. You're ready to sand and recoat when you can't smell the old finish any more. I use more coats in areas that see occasional water and/or lots of wear.
If I want to warm the color of the wood, I use watco clear for the first coat instead of wipe on poly (brush on, wait 10 min, wipe off). It adds a great "warm amber" cast to the finish. Finish off with 0000 steel wool and burnish with cotton toweling, or use polishing compound to get that elusive mirror finsh.
Using a thinned wipe-on finish is something that should help. A friend of mine put it together years ago and it has worked well for many. It will generally give a finish with minimal defects.
QUOTE
There are a number of suggested application regimens that are totally subjective. The number of coats in a given day, the % of cut on various coats, which coat to sand after, when to use the blade and a whole host of other practices are all minor differences between finishers. There are some things that I consider sacred when applying a wipe-on finish.
If you are making your own wipe-on the mix is scientific - thin. I suggest 50/50 because it is easier to type than any other ratio and easy to remember.
The number of coats in a given day is not important. Important is to apply a wet coat with an applicator and merely get it on. Think of a 16 year old kid working as a busboy at Denny's you have sent over to wipe off a table. The applicator should be wet but not soaked. The applicator can be a paper towel, half a T-shirt sleeve or that one sock left after a load of washing. Then leave it alone. The surface should not be glossy or wet looking. If you have missed a spot, ignore it - you will get it on the next coat. If you try and fix a missed spot you will leave a mark in the finish.
Timing for a second coat involves the pinkie test. Touch the surface with your pinkie. If nothing comes off you are ready for another coat. It was tacky 5 minutes ago but not now. Apply your next coat just as you applied the previous coat. Remember, you are wet wiping not flooding. After applying the second coat, let it fully dry for 48 hours. Using 320 paper and a sanding block ligthtly sand the surface flat. Now, begin applying more coats. Do not sand between coats unless you have allowed more than 24 hours to elapse since the prior coat. Keep going till you are tired of it. The number of coats is not critical - there is no critical or right number to apply. For those who need a rule, four more coats on non-critical surfaces or six more coats on surfaces that will get abraded seems to work.
After your last coat has dried at least over night you will have boogers in the surface. You should not have marks in the surface because you ignored application flaws. You may have dust, lint and, if you live in Texas, bug legs. Use a utility knife blade at this point. Hold it between your thumb and forefinger, near the vertical, and gently scrape the surface. Gentle is the important word - no harder than you would scrape your face. If you start scraping aggressively you will leave small cut marks in the surface. After you have scraped to the baby butt stage gently abrade the surface with 320 dry paper or a gray ScotchBrite. Clean off the surface. Now, leave the area for two hours and change your clothes. Apply your last coat with a bit more care than the previous coats and walk away.
An anal person is going to have a tough time with this process. Missed spots have to be ignored. Wet wipe, don't flood. Scraping to babies butt smooth means scraping no harder than scraping a babies butt. Ignoring any of these will leave marks that are tough to get out. Getting these marks out requires some agressive sanding to flatten out the surface and starting over.
Jim Kull
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Finally, It works better to use a gloss varnish for all coats except the last. The flatteners in semi-gloss and satin tend to rapidly fall out of suspension when the finish is highly thinned. If you want a non-gloss finish, use it only on the final coat or two and be sure to stir the material frequently or you will end up with cloudy streaks.
"nibs"
to reduce these, you have a few options: add a small amount of japan drier to the poly, but don't overdo it(read the label). This speeds drying time to reduce impurities landing on your work. If you don't have a dedicated spray booth, I'd mist the air with water thoroughly then sweep/vacuum all dust before starting.
With polyurethane, brushing can work as well as spraying,though spraying is easier in achieving a uniform coat. Initially. What matters next is the difference between a good finish and a great finish. When the second or third coat is dry, an automotive polisher with different compounds can take the gloss level up, or down, wherever you want it. Be sure to use a quality polyurethane; I've used cheap ones, soya based that were near impossible to dry hard.
I am not a fan of any wiped-on finishes that intend to offer protection; the mere fact that they are thinned enough to wipe on means they don't have enough solids. A labor intensive Pyrrhic victory at best.
Since you've got spray equipment, I really recommend lacquer;dries fastest looks great.
Edited 6/10/2005 2:46 pm ET by jackplane
I used 1/4" tempered glass top for mine. Great finish LOL
Thanks everyone for giving me your experiences with applying poly. I bought a new can of it this afternoon and will give all of these methods/techniques a try on some scrap pieces and then decide on what I can make work best/easiest. Will take a try at spraying it last since I do not have a spray booth.
Don
Most everyone that responded to your query has assumed you were looking for advice on wipe-on poly. Is that what you want, or are you looking for info on brushing?EDIT: I think there are other, better products for spraying, if that's what you want to do. ********************************************************
"I tend to live in the past because most of my life is there."
-- Herb Caen (1916-1997)
Edited 6/11/2005 1:54 am ET by nikkiwood
I had planned on brushing it on, however, after reading the posts and visiting the local paint store and talking to a retired "finisher" in the store he convinced me to try wiping it on with a lint free rag as a start (to avoid the issue of nibs I have always experienced in the past). Wiping is going to require more coats to get the needed amount of protection. Although, he did state that the spray method would give the best results but since I do not have a dedicated spray booth, I am reluctant to try it on poly to begin with.
What is your experience with spraying? Do you use something other than a poly finish if you are spraying a piece of furniture? Although I have a large workshop, I am sure dust would be an issue. When spraying in the past, I have waited until weather conditions were ideal and just sprayed things outside of my shop on a table or whatever.
Don
Slow drying finishes like poly varnish can be problematic when spraying. Unless you spray outdoors or have dedicated space or spray booth, the overspray will get all over everything in the area. You will have a crust of poly on everything.
Spraying also raises dust and can lead to more little dust nubs than brushing. In the shop I was involved with, we sprayed varnish after cutting it 50% with acetone. This caused it to "flash off" or become dry to the touch faster. The faster flash off meant we could get a second coat on faster and there was less chance for things to mar the surface. Even though it flashed off faster, the finish still took as long to fully cure.Howie.........
I never got around to answering your question, in part because Howie said what I would have. I really don't see the point in spraying poly, since lacquer is so much easier (faster drying). And the catalyzed lacs, I think, are every bit as durable as poly -- maybe even more so.********************************************************
"I tend to live in the past because most of my life is there."
-- Herb Caen (1916-1997)
Could keep my mouth shut and not show my ignorance I suppose, but are all lacquers "catalyzed lacquers"? Or is this a new product? I haven't heard that term used to described any woodworking lacquers.
Don
Edited 6/22/2005 11:21 am ET by ardmore
Never, ever keep your mouth shut around here................There are three basic solvent based lacquers I know about: nitrocellulose is the old standard -- fast drying, easy to use, easy to clean-up. The catalyzed lacs are two part (kind of like epoxy glue) -- mix up the two parts just before you spray; stuff has a limited life once mixed, and they are much tougher than their nitrocellulose cousins. There is a third, in-between type -- call precatylized. It is premixed for you, and is used the same as the nitrocellulose stuff. I have used quite a lot of it (from M.L. Campbell), since my supplier told me it is "tougher" than regular nitro. I like it, but it is difficult for me to tell if the claim is really true. I have a friend who has tried a new, water based lacquer ( from Homestead, I think). He says it is easy to spray, but to my eye, the finished piece I saw didn't have the depth and glow that you get from the solvent based lacquer products.********************************************************
"I tend to live in the past because most of my life is there."
-- Herb Caen (1916-1997)
Do you know what the slelf life is for precatlizes lacquer?
Have a nice day Lee.
Sorry, but I can't remember -- it's been a couple of years since I used it. Also, I always bought what I needed, and managed to use it up. so shelf life wasn't an issue. 6 months or a year sticks in my mind, but someone else should answer the question.********************************************************
"I tend to live in the past because most of my life is there."
-- Herb Caen (1916-1997)
shelf life should be on the can... Well, for the un-opened can.. I just use it for cars.. Not on wood.. I can get a good finish on metal but NOT on wood.. Just me... I think...
Once opened.. I use all of it or throw sawdust in what is left to dry it up so I can throw it away....
EDIT:: lacquer that is...
Edited 6/23/2005 2:08 pm ET by Will George
Could keep my mouth shut and not show my ignorance ..
I just LOVED THAT one... I do it when Opening my mouth all the time.... Never stopped me!
I've used minwax spray poly with success in the past. The key is to apply light coats. The cans have fan patterned spray tips that work very well. The negative is the cost. A good mask is helpful too.
There are more old drunkards than old doctors. Ben Franklin
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