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Spray Lacquer Help Needed

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Forum topic by Jim Savage posted 11-29-2010 04:34 AM 11338 views 1 time favorited 12 replies Add to Favorites Watch
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Jim Savage

26 posts in 2659 days


11-29-2010 04:34 AM

I’m trying to finish a project with spray lacquer, and it’s not going well. (If it was going well, would I be asking for help?)

I’m getting lots of drips. I’m trying to spray lightly, but if I go too lightly it doesn’t seem to cover, and there’s a very fine line between spraying too lightly and spraying too much.

Should I be spraying several light coats? (By several, I mean 6 or more. I’m trying to be done in three coats, and maybe that’s why I’m trying to spray a lot for each coat.)

Should I be spraying only horizontal surfaces so the finish doesn’t run? (That would entail turning the project several times so the surface being sprayed is always horizontal.)

Should I just use brush-on or wipe-on finish?


12 replies so far

View dakremer's profile

dakremer

2583 posts in 2554 days


#1 posted 11-29-2010 05:39 AM

while i’m no expert….i have used it before and can offer this advice. lighter (and more) coats is way better than thicker and less coats. if you are getting dripping – you are spraying on too heavy. unlike shellac, it does not “eat” into the previous coat, so any imperfections from the previous coat will show through (correct me if i’m wrong if anyone else is reading this). You have to sand between each coat with a high grit (320 or so) or some steel wool just to knock off the high spots, or dust spots or whatever. No need to turn the projects. If you are spraying light enough, the vertical pieces should not drip. i believe if you are trying to get that nice smooth finish you’ll need at least 6 coats. Hope that helps! Recently i’ve been big on Wipe-on-poly. You can wipe it on with a rag, sanding between coats….hope that helps?

-- Hey you dang woodchucks, quit chucking my wood!!!!

View Dark_Lightning's profile

Dark_Lightning

2633 posts in 2572 days


#2 posted 11-29-2010 06:03 AM

I love lacquer! You have to be careful how you spray it. The following applies:

1. Lacquer depends on temperature…you can buy “slow”, “medium” and “fast” thinner.
2. Sounds like you are using too slow a thinner in a cold environment, spraying too close, or spraying too slow (travel speed).
3. You can melt the lower layers, if they went on dry, by spraying straight thinner, carefully.

I’ve had excellent results with lacquer, painted cars and furniture with it. Those cars were not on rotisseries- I painted hoods, fenders, doors, etc, with the same gun and mix ratio of paint and thinner. You’ll just have to play with it some.

For newbies, I’d recommend spraying it a little dry and then carefully flowing it out with thinner. I’ve gotten dead smooth surfaces with just the gun, no polish. But that takes a bit of practice.

-- Random Orbital Nailer

View KnotWright's profile

KnotWright

252 posts in 2951 days


#3 posted 11-29-2010 06:07 AM

What temperature are you spraying at? is it cold where you are spraying? Humidity can sometimes cause problems when spraying lacquer.

I use a lot of Sherwin Williams pre-catalyzed lacquer and have had a few problems with runs from time to time, usually when I’m rushing to get that “perfect” finish. As previously stated, lighter/thinner coats are always best and easier to sand out any runs if you get them.

Also what size tip are you using to spray the lacquer with? You might ask your paint store to recommend the correct size tip for you to help with spraying. Too large a tip might be causing your problems.

-- James

View Bill Davis's profile

Bill Davis

226 posts in 3387 days


#4 posted 11-29-2010 10:59 AM

I like spraying lacquer too. I certainly wouldn’t brush it. Lacquer has volatile thinners so it dries fast and shouldn’t run. But you can spray too thick and it will run on a vertical surface. On vertical surface more and lighter coats better. I have sprayed multiple thick coats on a horizontal surface. You mentioned drips and runs. In my mind they are different types of flaws but from context I think you are referring to runs which as I said is caused from spraying too thick on a vertical surface. A fine tip is best with lacquer. Lacquer is an evaporative type finish so the solvent in the second coat redisolves the first coat and they then bond together as one. I’ve never tried spraying just the solvent on a coat. Not sure why you would. Spraying on the next coat is all I’ve ever needed. I usually sand lightly after the first coat then do several coats to build thickness then sand as required on the last coat to the sheen I want.

View Kent Shepherd's profile

Kent Shepherd

2717 posts in 2749 days


#5 posted 11-29-2010 08:54 PM

There are lots of variables in spraying lacquer that will affect the outcome. Are you using spray cans of lacquer? If so, that could be the problem. If using a gun, what kind? Are you thinning the lacquer? Too much thinner will cause runs. 3 coats will not generally give a good finish unless maybe you use an airless, in which case you don’t have to thin much.

More details would help to determine what the problem is.

-- http://shepherdtoolandsupply.com/

View CampD's profile

CampD

1474 posts in 2949 days


#6 posted 11-29-2010 10:08 PM

Remember,, 1st Coat is sprayed light to “seal” the wood as it will raise the grain. I let this coat throughly dry then a good sanding to remove all the nubs (raised grain) usually 220-320 grit.
Remaining coats are also sprayed thin, dont try to fill-in dry spots while spraying (ignore the temptation to go back over it while its wet) use the next coat to fill in that area. As mentioned Lacquer dries quick, muiltple coats can be done in a day and use 400 to sand between coats, I’ve even ended up using 1000 to get “that” glass finish and finish with paste wax, buffed ofcourse.
Also what tip are you using, should be smallest one for that gun.
and as said, use the proper thinner for the outside temp.

-- Doug...

View lashing's profile

lashing

109 posts in 2284 days


#7 posted 11-30-2010 12:56 AM

Lacquer is all I use. It does “eat” into previous layers. Very forgiving stuff. Nitrocellulose sticks to itself more than whatever you are spraying. Thus it blends into itself very very well.

If you are getting runs , one reason only – to much material in that spot. This can be because its to thin, simply to much altogether or you are going to slow.

I like to spray my lacquer at a pretty low PSI. I use an extra guage at my gun inlet to set this. I keep the copressor running 100, let 60 out and keep it down to 30 at the gun. This gives me a nice smooth finish and all the air pressure I need continuous for my needs. All with a small compressor.

I have to play with a new gun to learn its game so you’ll have to play with your I suppose. My few rules of thumb are thinner 2 to 1. As in two parts lacquer to 1 part thinner. After sanding I will do a 50/50 coat. When I do it right – the finish is so smooth and glossy no buffer could improve upon it. I can be tough to do right though as any overspray will have me wetsanding and buffing anyway.

I do get runs from time to time. Its when I get lazy figure I can exceed the allowance and/or go for another coat to soon. Nitro dries so quick that its easy to think you can spray it again. However the last coat has not flashed off and adding another gives you much more soft material than you might think you are putting on. It will run.

The best news is runs are very easy to fix. When you get a run STOP. Let it dry. the run will be far less off when you come back to it and nitro settles nicely as well. Scrape off the run with a razor and then shoot a thinned coast over top. All marks will be gone.

I have even finished jobs with an ultra thinned coat well beyond 50% thinner. You just have to be carefull. You spray just enough and slow enough to wet the surface and move on. Any hesitation will run. Done right it will look like smooth glass.

Anyway I ramble. Hope it helps a little. Also – when I started using lacquer I got runs and bad orange peel for quite a while before I learned how to thin, air pressure, gun settings, etc. Maybe its time to grab some scrap and learn your new medium. You’ll get it – I find finishing to be one of those things you can only learn by messing up for awhile first hand.

View dbray45's profile

dbray45

3185 posts in 2239 days


#8 posted 11-30-2010 05:07 PM

I love lacquer but cannot spray it because my shop is inside my house and the fumes become an issue for me. Brushing is my only way to apply so I have learned how to deal with unevenness. As a rule, I wet sand every coat with 500 grit to 1000 grit. On the final coat I smooth out with 1000 and then move to #4 pumice and finish polish with rottenstone. As a wetting agent, I use mineral spirits. Finish with carnauba wax and buff to a mirror finish.

The end result are 6 coats of finish that combined are less than the thichness of piece of paper and glass smooth. I do the same with poly.

-- David in Damascus, MD

View wwbob's profile

wwbob

111 posts in 2338 days


#9 posted 11-30-2010 07:52 PM

I just discovered tinted lacquer, Dunn-Edwards brand. Thinned with … wait for it … Acetone, max thinning 10%.

My first test was wonderful. Beautiful color, sprayed on easy and smooth flat finish, even with a guy who has owned a spray gun for just over a month with a Harbor Freight spray gun. Been spraying and learning with sanding sealer and clear lacquer.

Another lacquer wonder. I got a foot long scratch on a project I had just put on 4-5 coats of clear lacquer a week earlier. Quick hand sand with 220, three coats of lacquer and you can’t see the scratch. In exactly the right light angle you can see the depression from the scratch. My instructor says I could fill in the depression with more lacquer, but that isn’t required.

You gotta love it.

-- "I like the quiet I hear." - Channing, age 4

View wisno's profile

wisno

88 posts in 2474 days


#10 posted 12-01-2010 08:16 AM

You need the right spraying technique to get the good result.
Too much material will result the material drip and running, while to thin application may result in a uneven coat.
You may need some more practice to master the spraying technique, and also some more time to get use with the materials.
Just keep practicing and you will get the best result.

How to use the spray gun in the wood finishing.

Wisno

-- http://www.wisnofurniturefinishing.com/

View tomd's profile

tomd

2027 posts in 3233 days


#11 posted 12-01-2010 09:14 AM

You did not say if you are using rattle cans, if you are remember they are very thin. Try several very light coats, then fine sandpaper then more fine coats. Allow plenty of time between coats.

-- Tom D

View aurora's profile

aurora

228 posts in 2715 days


#12 posted 12-01-2010 11:44 PM

not sure if a set ratio is the way to thin paint, as temperature and humidity also effect the viscositiy. the same ratio you use on a hot day does not work on a cold humid day. because of this, many professional shops use a Zahn cup to measure the thinned mixture in number of seconds for the mixture to flow out of the cup. this thinning method accommodates for the temp effect on viscosity of the paint. the paint and equipment manufacturers should have a specification of what the sprayed viscosity (or Zahn cup reading) should be.

secondarily, the type of solvent used has a bearing on the dry time (or perhaps run time is a better description), with fast flash off solvents being used on cool days and slow flash off solvents used on hot days. the solvent is used to thing the paint mixture to a sprayable viscosity as measured in your Zahn cup. on a cool day you thin down your paint to the correct viscosity, but, ... need to use a fast solvent to flash off quickly because there is not the normal heat in the air to cause it to evaporate fast enough, ... and you will get runs. on hot days it works in reverse to keep you from loosing so much solvent to evaporation in the air while spaying that the surface looks like orange peel, and has no ability to flow out into a smooth surface.

solvents are classed as low temp, mid temp, or high temp.

trial and error method: #1 select the right temp solvent for the ambient temp you will be spraying in. #2put some cardboard sheets with the painted surface in the vertical. keep thinning paint in your gun until it just starts to spray. slowly add thinner until it flows out smoothly on the vertical panels. wait a few minutes to see if it runs on the vertical panels, if it doesn’t, you got lucky and can paint with this mixture. if it does run, you know how much solvent to add to the paint for this particular temp day, you just need the solvent to evaporate from the surface faster. a professional autobody paint retailer can direct you to a faster solvent. generally paint thinner/mineral spirits are slow evaporating solvents.

hope it helps.

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