Poly Questions

[Jason Christenson]

I'm in the middle of refinishing my wifes dining room table and am not happy with the finish I'm getting. I'm using a brush on poly finish.

Can anyone give me any advice on how to do this? I don't have access to a sprayer so spraying is not an option unless I try aerosol, is that worth a shot?

Any advice would be appreciated.

Jason

[John Huber]

Jason, What problems are you having? Brush marks, bubbles, etc.?

[Matt Tawes]

Without knowing the details of what's wrong I would just say sand the finish level with 220 grit, clean it off with MS looking for further brush marks then.... thin your poly by about 25% with MS and hand rub on a couple of coats with a cloth (no brush) buffing between coats with 0000 steel wool and you will get a beautiful and durable finish.

[Jason Christenson]

Jason, What problems are you having? Brush marks, bubbles, etc.?

John, the problem I am having is bubbles.....I think!

[John Huber]

If your problem is bubbles, there are two solutions that I can think of. In either case, you must sand off the offending fininsh. BTW it is important that you follow the temperature and humidity recommendations. All bets are off in cold or humid conditions.

Brushing polyurethane can produce bubbles. You can eliminate them by "tipping off" which means the last stroke of the brush is nearly vertical, very light pressure, and only a little finish on the brush. This technique takes a lot of practice. At least for me it did.

The other solution is a wipe-on finish. There was a comparison review article in Fine Woodworking Magazine July/Aug 2005 #178. My favorite is General Finishes Seal-a-Cell and Arm-R-Seal available at Woodcraft stores. I did a side-by-side test on walnut and could not tell the difference between the GF finish and Minwax polyurethane. They both "popped" the grain and neither could be scratched with anything short of sandpaper.

In my opinion, wipe-on finishes have several advantages over brush-on polyurethane:
1. No brush marks
2. No bubbles
3. No clean-up; just throw the foam brush or rag away.
4. No sweaty sanding off the excess finish to limit build-up while filling grain pores; just wipe off the excess finish with a rag.

[Don Baer]

Like John,
I am a real fan of wipe on poly for finishing. Since I don't spray I found that it give me the best finish. Just like the Karate Kid. Wipe on wipe off..:D

[Jason Christenson]

Wipe on poly sounds like a solution, do I have to specifically buy wipe on poly or can I just thin what I have with mineral spirits like Matt suggested?

[Jim Becker]

Jason, an oil-based varnish out of the can can be thinned 50/50 with mineral spirits to make a wiping varnish...and at less cost than buying it "pre-thinned". Just remember that with polyurethane varnish, you must scuff it if you let a previous coat dry for more than a few hours before the next coat. It just plain doesn't like to stick to itself.

[Jason Christenson]

Ok, I'm gonna mix some of this up and give it a try. Can I mix it in bulk and store it? If I do, can I store it in rubbermaid? Tupperware?

Jason

[Don Baer]

Jason,
I don't know if I chance putting it in any sort of plastic container. You can buy a new metal 1 gal paint bucket with a lid from the borg pretty cheap.

[Rob Blaustein]

Jason--I assume you're talking about an oil-based poly finish, right? I ask because as I've learned recently both from wiping and brushing on waterbased poly finishes and reading about them, there are some important differences that would be worth knowing if you are in fact using them.
-Rob

[Rob Blaustein]

My favorite is General Finishes Seal-a-Cell and Arm-R-Seal available at Woodcraft stores. I did a side-by-side test on walnut and could not tell the difference between the GF finish and Minwax polyurethane. They both "popped" the grain and neither could be scratched with anything short of sandpaper.
I did a similar experiment recently on some walnut veneered ply and didn't find that the GF combo and Minwax were the same--I thought the Minwax looked a bit duller with less grain popping. I applied (I think) four coats and I was using satin for both finishes but I wasn't adhering to the usual rule of building with gloss for several coats and applying satin only on the last coat. Maybe it would've been different had I done that. But I also compared those two to Bartley's gel varnish and I thought that came out the best, FWIW. And it was the easiest to apply.

[Jim Becker]

Ok, I'm gonna mix some of this up and give it a try. Can I mix it in bulk and store it? If I do, can I store it in rubbermaid? Tupperware?

If you don't have some jars lying about, HD carries empty 1 gt paint cans for cheap. I often buy them to use for storing a "custom" mix or to transfer finish from a larger can once its volume is reduced. I don't recommend you use plastic containers, not only because they cost a fortune, but because some finishes might react.

[John Huber]

I did a similar experiment recently on some walnut veneered ply and didn't find that the GF combo and Minwax were the same--I thought the Minwax looked a bit duller with less grain popping. I applied (I think) four coats and I was using satin for both finishes but I wasn't adhering to the usual rule of building with gloss for several coats and applying satin only on the last coat. Maybe it would've been different had I done that. But I also compared those two to Bartley's gel varnish and I thought that came out the best, FWIW. And it was the easiest to apply.

Rob, I should have said that both the GF and Minwax were gloss for all five coats, with the Minwax sanded aggressively between coats to minimize build-up while fillling the pores. Previously, I have used multiple coats of Minwax satin and found that it tended to give a milky appearance. Dunno if that is what you saw.

[Jason Christenson]

sanded aggressively between coats to minimize build-up while fillling the pores.

You guys keep saying that. What exactly does it mean and why is it necessary? Maybe you could give me your whole process, step by step, if you don't mind. It may shorten my learning curve. :)

[Rob Blaustein]

Rob, I should have said that both the GF and Minwax were gloss for all five coats, with the Minwax sanded aggressively between coats to minimize build-up while fillling the pores. Previously, I have used multiple coats of Minwax satin and found that it tended to give a milky appearance. Dunno if that is what you saw.

John, that's interesting that you've seen that milky look when building up satin Minwax. I don't know that I would use milky to describe it, but it was definitely duller and I don't just mean flatter (i.e. less glossy). Next time I'll do it the right way and build with gloss--it makes more sense given the two formulations. But what do you mean by sanding aggressively between coats--something Jason was asking about too. I've asked about sanding between coats here (http://www.sawmillcreek.org/showthread.php?t=32665) before and people seem to suggest very light sanding.

[John Huber]

Here's my polyurethane finishing process, part learned from books, part from the school of hard knocks. Although I no longer use it, having converted to wipe-on finishes. Read the books on finishing by Flexner and Jewitt.

0. My goal is to get a finish that my wife calls, "As smooth as a woman's skin." Some of the wood pores are just visible and you can barely feel them, but not smooth as glass. Touching it is sensual.
1. Choose good wood and build it the best you can. Even the best finish looks poor on cheap wood or bad construction.
2. Sand raw wood down to 220 grit, vacuum, and wipe with tack cloth.
3. Thin the first coat of gloss polyurethane 50:50 with mineral spirits. This is the sanding sealer. Use a top-quality badger tail brush, costing $40-50; cheap brushes leave brush marks and bubbles. Let it cure overnight, no matter what the label on the can says.
4. Scuff sand with 220 grit, vacuum, wipe with tack cloth. Apply full-strength gloss varnish sparingly (with the brush just wet enough to avoid skipping spots). You are trying to get the wood pores filled, but not build up a thick coating and a plastic look. Let it cure overnight.
5. Aggessively sand with 220 grit. This means sanding until no pores are visible after vacuuming off the sanding dust. Don't worry, the pores will show up later. Use stearate-coated paper, costing $0.50-1.00 a sheet. Cheap paper clogs and results in uneven sanding.
6. Repeat varnishing step above. Examine the pores. Repeat the sanding-varnishing steps as needed. For walnut, this is often 5-7 coats.
7. For the last coat, sand down to 320 or 400 grit. Depending on your skill in not leaving brush marks, you may want to thin this coating. If you want a non-gloss finish, use satin varnish for this step only or rub it out (see the books above).

This finish is a lot more work than the "two coats and you're done" that you might believe from the label on the can. Those instructions give a plastic look that has given polyurethane a bad name among fine woodworkers. This finish looks good; but it is a lot of physical work. Wipe-on delivers the same or better finish with a lot less work.

[Vaughn McMillan]

You guys keep saying that. What exactly does it mean and why is it necessary? Maybe you could give me your whole process, step by step, if you don't mind. It may shorten my learning curve. :)
Take this with the grain of salt worthy of my finishing rookie status, but I believe I can answer your questions. These are based on my own observations, so who knows...I could be missing something heree.

"Filling the pores", means exactly that -- filling the pores of the wood to even out the surface of the finished piece. If you put a clear coat of finish on a relatively porous wood (like oak, for example), the surface of the finish follows the ups and downs of the wood surface, pores and all. If you sand the piece mildly, you will remove the finish from the high spots on the wood surface, but still have finish down in the little pores of the wood. After another coat of clear finish, you should see fewer "ups and downs" in the finished surface (or none at all). Sometimes it takes several repeats of this process to completely fille the pores and get a glass-smooth surface. Eventually though, the last coat of clear finish will be absolutely glass-like (after some additional rubbing out and polishing).

Why do it? As far as I know, It's strictly a preference thing. Some people like to see and feel the porous nature of the wood, and others prefer the glass feeling. To some, the glass finish looks too plastic, and they prefer the organic feel of a more natural finish. I like the porous look and feel on some pieces, and on others I like to try to fill the pores and make the surface absolutely smooth. (Which also involves a lot of work with progressively smoother abrasives down to polishing compound.)

Here's an example of a porous wood (padauk) with the pores filled and finished to the "wet glass" look. I built up the finish with many coats of General Finishes Arm-R-Seal, sanding each coat off until the pores were filled, then I added another boatload of coats before rubbing it out with 320, 400, 600 and 1200 grit paper, then polishing with rubbing compound and polishing compound. Although I didn't do it on this particular box, Ive since learned that water (or some other lubricant) is your friend when rubbing out a finish like this:

35022

And here's a detail shot of a cutting board showing some porous wood that still shows the pores. The dark wood is jarrah, and it's got a lot of pores. This one is simply sanded down to 400 grit, then soaked in mineral oil for a day or so, then wiped dry. Although this picture doesn't show it great, you can see the difference in porosity between the jarrah and curly maple...

35023

I hope this answers your questions, and if I'm real far off base I'm sure someone will educate us both. ;)

- Vaughn

[John Huber]

Vaughn,

Don't be so modest! Your description of what it means to fill the pores and why is very clear, concise, and comprehensive (as my old English teacher would say). Your phots show the results very clearly.

[Jason Christenson]

Ok, after a long hiatus, I am back to work on this project. Can anyone give me their step by step wipe on technique.

Thanks a million.
Jason