Spraying polyurethane - Woodworking Talk - Woodworkers Forum

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post #1 of 24 Old 10-14-2008, 11:26 AM Thread Starter
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Spraying polyurethane

Well, I'm almost through with Mrs. Smith's jewelry cabinet...my first production project in my new shop that wasn't something for the shop.

I've asked around, and been thinking about this the whole time I was building...I used my automotive spray gun to shoot polyurethane once I was ready to varnish. Man, guys, I have to tell you....this is the way to go .

I hung the drawers from the ceiling by the hole I predrilled for the drawer pull, and set the case up about waist-high. I rigged up some ventilation with box fans. I wore a mask, and after the first coat, I took off my glasses while shooting.

The end result is going to be good. Very good, I think. It will definately be the best coat of poly I've ever put down, having only ever used foam or natural brushes until now. I don't think I'll ever go back to that method on a project of any size....

pictures will follow...

regards,
smitty
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post #2 of 24 Old 10-14-2008, 12:14 PM
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Smitty,

Wait till you try lacquer. Just my 2¢ but I'll never go back to Poly.

Main difference is lacquer will dry quick, much less dust, etc stuck to finish, it melts into and combines with previous coats making a more durable and a glass-like smooth finish.

I've used the water based stuff as well. Not even close finish wise.

If you have the equipment, including a good gun, respirator and ventilation you should give lacquer a try.
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post #3 of 24 Old 10-14-2008, 12:37 PM
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yea i have to agree with the lacquer i always put 1 coat of sanding sealer then sand with 220 then 2 coats of high gloss lacquer but if you like the poly look you could try satin lacquer
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post #4 of 24 Old 10-14-2008, 01:28 PM
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" I've used the water based stuff as well. Not even close finish wise." I am not sure what you are saying here. Are you saying the water based lacquer is not as good as regular lacquer.

I recently had good luck with the Target Coatings water based lacquer.

George
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post #5 of 24 Old 10-14-2008, 03:22 PM
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The water base lacquer raises the grain a lot more, takes longer to dry, cannot be used with spray toners and is a pain in the *(&^to repair if it gets damaged.
Lacquer finishes dries in minutes. An entire 5 piece bedroom set can be completely stained and finished in one day easily.
For tables, end tables and anything that is likely to have something wet or warm put on them, look for vinyl sealer and acrylic topcoat. They are both lacquer based products and are compatable with toners and shading lacquers!
Lacquer finishes are easily repaired and are durable and excellent looking. Polyurethane finishes are very difficult to repair and take an extended time for drying. They are, however, a very durable finish.

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post #6 of 24 Old 10-14-2008, 04:18 PM
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Quote:
Originally Posted by GeorgeC View Post
" I've used the water based stuff as well. Not even close finish wise." I am not sure what you are saying here. Are you saying the water based lacquer is not as good as regular lacquer.

I recently had good luck with the Target Coatings water based lacquer.

George
Sorry I should have made a clearer statement. The original OP was talking about Poly. I've used the water based poly and wasn't happy. Never tried the water based lacquer.

Clockdaddy makes the point I was refering to earlier. Drying time is always an issue. In the best of circumstances a quicker dry time means less dust stuck to the finish. Especially noticeable on surface items like table tops. The other point worth mentioning is when you sand between coats using a solvent based lacquer you don't ever get witness lines from sanding through one coat down to the previous coat. Not all water based product will burn-in to the previous coat. Solvent based lacquer does burn-in and totally eliminates this problem.

Just my preference over the years. I don't mean to knock what others are having success with. Not my intent at all.
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post #7 of 24 Old 10-14-2008, 06:37 PM
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No pics....didn't happen! Alright I know you'll get em up soon. I haven't ever sprayed any finish but that is something I would like to pursue. Sounds like it worked out well for you. I'm sure the Mrs. will be very happy.

John
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post #8 of 24 Old 10-14-2008, 07:21 PM Thread Starter
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Hey John: you ain't been around lately....boss-man must be keeping you busy! I'll get pictures soon as I get the felt cut.

Guys, thanks for the tip on the lacquer. I will definately look into it, since the cure time on the polyurethane eats up most of a good day.

thanks
smitty
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post #9 of 24 Old 10-17-2008, 12:19 AM
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I agree with most.

I use pre-catalized or catalized nitrocellulous lacquer which is a furniture grade lacquer. Dries dust free in about 5 minutes, You can handle it lightly in 10 minutes. Recoat in 12 - 15 minutes. That means 5 coats in one hour. That means you are DONE !!!!
Note that cheap cabinet grade lacquer is a poor product and good furniture grade lacquer is a great product. When I use catalized or pre-cat on a table top or desk top, customers ask what kind of wax did I put on. Yes, it's that slick. The next question they ask is "what should I clean it and maintain it with?" Answer: a damp rag.

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post #10 of 24 Old 10-20-2008, 03:34 PM
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I'm in the same situation. I just sprayed on a coat of oil based poly and I'm not impressed yet. Am I better off going with multiple very thin coats (almost to the point you can't see anything going on), or applying heavier coats and allowing it to flow together?

Where can you get the furniture grade lacquer? Sounds like that is what I should have done instead of poly.
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post #11 of 24 Old 10-20-2008, 04:20 PM
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Any finish should be applied using thin, even, multiply coats.
After each coat is dry, the item should be scuff sanded to knock off any roughness, wiped down with a tack cloth or blown off thoroughly with an air gun.
About the only finish that is applied in a heavy coat is decoupage which is an epoxy based finish that is poored over tables and the like, allowed to self level and dry.
CD

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post #12 of 24 Old 10-20-2008, 04:23 PM
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Furniture grade lacquer can be purchased at numerous paint supply store. An excellent finish is from Sherwin Williams. Their water resistant finish is good quality and durable!.

CD

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post #13 of 24 Old 10-20-2008, 05:13 PM
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Personally I'm a diehard oil base poly fan, especially when it comes to something that I'm doing for myself. I once thinned some out and sprayed it in a automotive spray gun, never again, the finish turned out well, but man, the air got so think with it that if I'd ever tried that again it would only be with a HVLP gun. I can see laquer as bein something to use if your selling a piece and time is money, but for durability I don't think you can beat a oil base poly. Just my opinion.
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post #14 of 24 Old 10-20-2008, 05:29 PM Thread Starter
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Quote:
Originally Posted by Woodchuck1957 View Post
...but for durability I don't think you can beat a oil base poly.
I think I'd have to agree with you Woodchuck. I have some lacquer for a quick project I'm throwing together in the shop (3 - 30" stools for the boys when we're working on something together.) I plan to use this project as a test bed for the lacquer, since I've never used it before, but I am quite accomplished at poly, brush and now air-applied, and do really like the way it stands up over time.

smitty
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post #15 of 24 Old 10-20-2008, 05:31 PM
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What is the best thing to thin it with, and what ratio? I am using an HVLP spray gun.
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post #16 of 24 Old 10-20-2008, 06:51 PM
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Spraying oil base polyurethane can finish off nicely if you have the time to wait and you are spraying in a controlled dust free spray booth. It takes too long to dry, and has the tendency to run if you aren't that experienced. It stays wet long enough for anything to land on it.

Acetone based (lacquer thinner) lacquer is very quick and was my mainstay finish for many years. It's extremely toxic and should only be sprayed in a well ventilated area, preferably a spray booth. It blushes very easy, and like all finishes, knowing the quirks and technique, make the difference in getting a good finish. I stopped using lacquer due to health reasons. Even with a respirator and a spray booth, it stays in the air, and being atomized gets on your skin, and can penetrate the body through any orifice, like eyes, and ears. Doing the mixing and cleaning permits toxic absorption into the body. You can't cover everything long enough. Acetone based lacquer may be phased out. IIRC, some states have banned it.

As for what's called "water based lacquer", manufacturers can call it whatever they want. It's base is basically ethylene glycol, which is similar to waterbased polyurethane. So, if you want to know what you've got, check the label for what thins it or cleans up with.

I spray primarily waterbased polyurethanes, and get an equivalent finish as I did with lacquer, without all the toxicity of lacquer, no blushing, and water clean up. There are WB poly's that are crosslinked and suitable for wood flooring.






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post #17 of 24 Old 10-20-2008, 10:47 PM
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What water based laquer are you using cabinetman? Most water based laquers I have used I can not get any build with them, because they do not have the "solids" in them that most solvent based laquers have.
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post #18 of 24 Old 10-21-2008, 07:37 AM
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What water based laquer are you using cabinetman? Most water based laquers I have used I can not get any build with them, because they do not have the "solids" in them that most solvent based laquers have.

Here is one that works good and is available at HD.






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post #19 of 24 Old 10-21-2008, 10:26 AM
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Hi Cabinetman
You sound like you are pretty happy with the water based polyurethane. I am going to refinish some maple kitchen cabinets doors, and my choices were to use lacquer, poly urethane, or varathane. Is there any downside to the water based poly? It sounds like it would be the best choice for spraying.
You also mention a cross link for wb poly for flooring. Another project I will be undertaking is to install and finish an oak floor in the kitchen.

Thanks
Gerry

Last edited by Gerry KIERNAN; 10-21-2008 at 10:28 AM.
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post #20 of 24 Old 10-21-2008, 11:06 AM
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Originally Posted by Gerry KIERNAN View Post
Hi Cabinetman
You sound like you are pretty happy with the water based polyurethane. I am going to refinish some maple kitchen cabinets doors, and my choices were to use lacquer, poly urethane, or varathane. Is there any downside to the water based poly? It sounds like it would be the best choice for spraying.
You also mention a cross link for wb poly for flooring. Another project I will be undertaking is to install and finish an oak floor in the kitchen.

Thanks
Gerry

Just a few tips. Depending on which one you use, you may want to thin, try 10% to start. I don't let the mix sit in the gun for any extended length of time, and I keep the tip and needle clean. It has a tebdency to clog due to fast drying. I try to spray parts vertically, so the finish doesn't "lay wet". I use a lot of light so I can follow a glare that tells me how wet I'm getting the surface.

The only "trick" is to get the pressure at the gun right so it doesn't spit, but rather is sufficient to atomize the mix. Getting a feel for the spraying distance, movement speed, and size/shape of the spray pattern. I try not to shake the mix. If spraying stops for a while, I'll pour out the gun to an "already thinned" type container, so I can just reuse. Immediately, I'll spray clean water through the gun. I always use strainers anytime fluid is poured into the cup.

Other than those few tips, that's about it. Some brands can be "crosslinked" with a catalyzer, which chemically changes its properties. I'm not a chemist, but I will say that I get an equivalent finish in both feel, build and durability to acetone based (lacquer thinner) lacquer.

In the picture below, the finish is satin WB poly.
.







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