polyurethane techniques

[OriginalChong]

When I polyurethaned my cabinet, it looked horrible. It was all bumpy and stuff. When we sanded it down between coats, it looked as if we took every off. So we stopped sanding it for the third coat. It looked pretty bumpy. The directions on the back of the min-wax polyurethanes are pretty vague. I'm trying to get a very professional looking coat of polyurethane. Does anybody have suggestions? Chris already recommended I switch to polyacrylate.

 

[NZAPP1]

You need to avoid bubbles in the finish. Here are a few ways to accomplish this. First, stir, don't shake, the can. Second, use a high-quality, natural bristle brush. Third, work the finish into the wood, but don't create excess foam. Fourth, "tip-off" the finish before stopping, carefully running the brush at a 45-degree angle the length of each board in one unbroken movement. This will burst and smooth out any bubbles that may have been created. I hope this helps.

 

[thrt15nc]

Poly's a "dust and anything else that might be in the air" magnet. When I use it, I set up a plastic drop cloth hood. Then I apply the poly to the piece, and then immediately put it back under the "hood" for it to dry. That really helps in keeping the junk off of it for me. You have to be gentle when sanding. Just enough to knock the nibs down.

Tom

 

[woodguy1975]

Take the can of poly and put in the the trash and use a real finish.

Seriously poly is tough to apply in such a way that you get a good surface build without streaks or bubbles. Try thinning by 50% and wiping it on.

For future projects get away from poly. It only belongs on floors in my opinion. Try Waterlox or Arm-R-Seal or some other wiping varnish.

Good Luck,

John

 

[WoodWrangler]

Step one - Stay away from Minwax products. Stop by Klingspor or Woodcraft and pick up some quality finish. Personally, I've been burnt one too many times by Minwax's inferior products ... and it can be a sure way to ruin a nice project.

Step two - Thin the poly a bit. In my limited experience thinning things makes them easier to work with. Yeah, you'll need more coats, but more thin coats is better than a few thick ones.

Step three - Drop $100 on a Wagner FineSpray HVLP system. It's a cheap way to get into the HVLP game and it works like a champ. With this you will be spraying the finish -- which can give a nice finish too.

 

[OriginalChong]

See, why don't they put that kind of stuff on the back of a can? "Stir, don't shake"... that's great advice. I wish I knew that.

Alright, so I have a lot of different questions now. I'm going to state them all and I'm sorry if I don't remember who said what... So, we have Arm/R... and Waterlox. What kind of material is used in that? How durable is it and what are the drawbacks? "Thin it out to 50%" meaning dilute with mineral oil?

Using a hood sounds like it's way too much work for me. Besides, I feel like it's still going to draw the dust particles in the vicinity of the poly/wet pieces. But I do like the advice about wiping it on. I did that with Tung Oil on another project and although it was hella easy, I didn't like the finish it left.

Spraying it on sounds like it would work but wouldn't that leave air bubbles? What are your experiences with that? Do you have to run it over with a brush afterwards? I might be willing to try that.

 

[jeff...]

Take the can of poly and put in the the trash and use a real finish.

Seriously poly is tough to apply in such a way that you get a good surface build without streaks or bubbles. Try thinning by 50% and wiping it on.

For future projects get away from poly. It only belongs on floors in my opinion. Try Waterlox or Arm-R-Seal or some other wiping varnish.

Good Luck,

John

John, I have to disagree with you on this one. Gloss polyurathane is by far my favorite finish. It works great thinning it out about 50 / 50 with mineral spirits and using a spray gun to apply it. I don't sand inbetween coats either because it creates little buggers on the sand paper and destroys the finish that was just applied. I rub the coats down with 00 - 0000 steel wool and gently wipe the finish down with a tack cloth to capture any dust and traces of steel wool before the next coat. When Poly sets up it's hard to beat it's durability, cleanability and longevity (hence also good for floors). I think the key is building up several thin coats, a thick coat isn't worth a hoot and takes way to long to dry. Thin coats dry just as fast as anything else. I have to admitt it's kind of hard to work with, but the results are well worth it in my mind.

Thanks

 

[dozer]

If you did shake the can instead of stirring then you might want to let that can sit for a couple of weeks and see if all the bubbles come out.

 

[Alan in Little Washington]

Thin it out to 50%" meaning dilute with mineral oil?

Thin/dilute with turpentine or mineral spirits, NOT with mineral OIL !!!!!!!

 

[rhett]

I always start with a wipe on then follow using a foam brush to apply additionat coats. It have found that by dabbing your wet foam brush every 8-12" along your stroke pass will make for a smooth flowing coat. Being methodical and keeping a wet edge are helpful. Using abrasive pads between coats also seems effective.



Prior Proper Planning Prevents **** Poor Performance.

 

[WoodWrangler]

Spraying it on sounds like it would work but wouldn't that leave air bubbles? What are your experiences with that? Do you have to run it over with a brush afterwards? I might be willing to try that.

In my experience, spraying a thinned Poly works great! I've even done it outside without a dust free environment and it worked well (though on a calm day). If you spray good, you won't have to brush it at all.

 

[rhett]

I think that if your going to spray, use laquer. Unless the application calls for a polyurethane durability.

 

[jeff...]

There used to be a product called urethane lacquer. It was awesome, sprayed like lacquer, setup like poly urethane. Once you started finishing you had 24 hours to apply all your coats, because it setup rock hard in 24 hours. That was many years ago though, last time I used it was in 1987. We still have a Thomasville coffee table in our living room that I finished with urethane lacquer in 1986, after all these years the finish is still top notch and the best part is you can clean it with windex. I don't think they sell urethane lacquer anymore; I seem to recall it was pulled for health reasons.

In my opinion with a little work a very tough and durable finish can be achieved with poly urethane, I think the key is thinning it out and building the finish up with light coats, I mean real light coats (mist coat). Take your time, like you do with a fine wine and I think you'll be plesently surprised when it's all said and done.

 

[woodguy1975]

John, I have to disagree with you on this one. Gloss polyurathane is by far my favorite finish. It works great thinning it out about 50 / 50 with mineral spirits and using a spray gun to apply it. I don't sand inbetween coats either because it creates little buggers on the sand paper and destroys the finish that was just applied. I rub the coats down with 00 - 0000 steel wool and gently wipe the finish down with a tack cloth to capture any dust and traces of steel wool before the next coat. When Poly sets up it's hard to beat it's durability, cleanability and longevity (hence also good for floors). I think the key is building up several thin coats, a thick coat isn't worth a hoot and takes way to long to dry. Thin coats dry just as fast as anything else. I have to admitt it's kind of hard to work with, but the results are well worth it in my mind.

Thanks

Jeff....

Poly doesn't belong on a fine peice of furniture. Especially gloss. You should hardly ever use gloss on a peice as well. The biggest mistakes newbies make are they use poly and they use gloss. I'm into traditional woodworking. The only finishes I'd ever put on a piece are shellac, lacquer, or varnish.

Sand thru a layer of poly one time and you'll never use it again. BTW, every see a peice in a museum with a poly finish.

NO POLY!!! Just stay away from them.

 

[Travis Porter]

I have used the Minwax for years. I agree with don't shake, stir.

You need to let the airborne dust settle and then wipe it down. Steel wool/rough it up between coats to give the poly something to bite into for the next coat.

The biggest thing I have learned, is to get a hand light and shine it on the piece from angles. You would be amazed at the runs and missed places you will find.

 

[woodguy1975]

There used to be a product called urethane lacquer. It was awesome, sprayed like lacquer, setup like poly urethane. Once you started finishing you had 24 hours to apply all your coats, because it setup rock hard in 24 hours. That was many years ago though, last time I used it was in 1987. We still have a Thomasville coffee table in our living room that I finished with urethane lacquer in 1986, after all these years the finish is still top notch and the best part is you can clean it with windex. I don't think they sell urethane lacquer anymore; I seem to recall it was pulled for health reasons.

In my opinion with a little work a very tough and durable finish can be achieved with poly urethane, I think the key is thinning it out and building the finish up with light coats, I mean real light coats (mist coat). Take your time, like you do with a fine wine and I think you'll be plesently surprised when it's all said and done.

Urethane lacquer is basically post cat lacquer. It has a catalysis that initiats cross linkage. After 24 hrs the cross linking is complete and an additional coat will not chemically bond and requires mechanical bond.

Big businesses us UV curable finishes that cure instantly when exposed to UV. Those finishes have UV inititors to kick start the cross linkage.

A cross linked finish is more durable because it will not redesolve in it's solvents, but they are not traditional. IF you've ever touched a rubbed out lacquer finish beside a rubbed out poly finish you'll choose lacquer every time. If you can spray you should spray lacquer. If that isn't durable enough spray a conversion varnish. Leave the poly to the floor. Have I said that enough this thread.

I've still got room in my finishing class if anyone is interested. We talke about all this stuff.

 

[erasmussen]

Jeff....

Poly doesn't belong on a fine peice of furniture. Especially gloss. You should hardly ever use gloss on a peice as well. The biggest mistakes newbies make are they use poly and they use gloss. I'm into traditional woodworking. The only finishes I'd ever put on a piece are shellac, lacquer, or varnish.

Sand thru a layer of poly one time and you'll never use it again. BTW, every see a peice in a museum with a poly finish.

NO POLY!!! Just stay away from them.

Very well said.
I love a lacqure finish, needless to say I have many things finished with japanese lacqure and after 35+ years there just as nice now as when I got them
Wish I could do lacqure, but I cant control a bursh right nrver could never will:crybaby2:, and I dont have spraying equiptment or room to spray.
But shellac I love its so easy to apply, I keep a pad for each type of shellac in an airtight container, just get 1# or less cut and wipe it on.
you can build it up to what ever thickness you like, if you get a spot that you dont like just rub it out:eusa_clap and with a little practice and effort you can get a panio shine:eusa_danc. even someone like me cant go wrong:lol::lol:

 

[jeff...]

Jeff....

Poly doesn't belong on a fine peice of furniture. Especially gloss. You should hardly ever use gloss on a peice as well. The biggest mistakes newbies make are they use poly and they use gloss. I'm into traditional woodworking. The only finishes I'd ever put on a piece are shellac, lacquer, or varnish.

Sand thru a layer of poly one time and you'll never use it again. BTW, every see a peice in a museum with a poly finish.

NO POLY!!! Just stay away from them.

J John, respectively if I had your talent and was into making what you make, I would agree with you, I would use a shellac, lacquer, or varnish, most likely lacquer. But us folks who are making stuff for everyday use, really need something durable, especially if kids are involved. Shellac, lacquer, or varnish are beautiful finishes in their own right, but I think you would agree their not all that durable. I also think you would agree they scratch and stain pretty easy?. I like the idea of being able to clean with soap and water or maybe even windex, I wouldn't dare try that with a shellac, lacquer, or varnish finish.

One of the main reasons I prefer gloss, is the sheen can always be adjusted downward, by rubbing out the final coat with fine steel wool or if your a real glutton for punishment, pumice or rotten stone. But flat simply can't can't be adjusted any higher than flat.

Everyone has their preference, that’s why there are so many different finishes out there. I try not to discount any of them; they all have their purpose in life. Ranging from a fine museum piece, to a young boys toy box.

Please keep in mind this is my 2 cents only and I'm not trying to be contentious in anyway. I'm sure you cover finishes and their intended uses in your finishing class.

Thanks

 

[OriginalChong]

I want to thank everybody who posted a response. This is my first time posting and it's become abundantly clear that this is a very helpful website. In less than 24 hours we've had two pages worth of postings. My gratitude goes out to all of you.

I know polyurethane is synthetic in nature and probably went into production about a hundred years ago or less. So, historically speaking it won't be found in antiques. I'm assuming they used Shellac or Lacquer? Can anybody tell me the chemical makeup of those two? Also, what about the finishes that were discussed earlier (Arm-R something and Waterlox)?

I think we can all agree that I'm not going to be building any showcase furniture for another couple of years. I'm just trying to make it so that I'm not embarassing myself when dealing with other "beavers".

And I just wanted to put this smiley up because I like it. :new_micro

 

[woodguy1975]

I want to thank everybody who posted a response. This is my first time posting and it's become abundantly clear that this is a very helpful website. In less than 24 hours we've had two pages worth of postings. My gratitude goes out to all of you.

I know polyurethane is synthetic in nature and probably went into production about a hundred years ago or less. So, historically speaking it won't be found in antiques. I'm assuming they used Shellac or Lacquer? Can anybody tell me the chemical makeup of those two? Also, what about the finishes that were discussed earlier (Arm-R something and Waterlox)?

I think we can all agree that I'm not going to be building any showcase furniture for another couple of years. I'm just trying to make it so that I'm not embarassing myself when dealing with other "beavers".

And I just wanted to put this smiley up because I like it. :new_micro

Arm-R-Seal and Waterlox are very similar varnishes. I think waterlox has a higher solids content so it builds a little faster, but they are both an oil/varnish blend. I like waterlox original. Stay away from the high gloss Waterlox. It is very tough to apply without streaking. You can get Arm-R-Seal (General Finishes product) from Klingspor's and Waterlox from Woodcraft or Homestead. Waterlox has a more amber tone that is really nice on walnut or cherry.

Good Luck,

John