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post #1 of 12 (permalink) Old 03-09-2013, 01:33 PM Thread Starter
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Default lacquer finish problem

I am using an aerosol lacquer. I sand the bare wood to 320 grit, apply sanding sealer and sand (sometimes multiple times), when the surface is uniformly flat and true I spray flat black lacquer and finish with a few coats of clear satin lacquer. It is driving me crazy that I continue to end up with some dull areas. I thought I finally had the situation rectified but after a day or so cracks developed and I was able to lift the finish. Does anyone have any ideas as to what I am doing wrong? As I said, it is driving me crazy.
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post #2 of 12 (permalink) Old 03-09-2013, 03:28 PM
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Are you using a lacquer sanding sealer? Cracking and lifting sounds like there's some non-compatible component in the mix somewhere. Or it may just be that you're sanding the wood too smooth for the sealer to grab, try a test piece sanded to 180.

Same brand for all products? Time between coats? How many clear coats? What wood species?
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post #3 of 12 (permalink) Old 03-09-2013, 05:49 PM Thread Starter
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billg71, both the sanding sealer and finish are from the same line of Behlen products. Too smooth of a surface would compromise adhesion but it wouldn't account for the dull areas when finsihed or, would it?
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post #4 of 12 (permalink) Old 03-10-2013, 07:07 AM
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Not sure where you are, but often when lacquer turns hazy/milky and lifts it's moisture - either ambient or the wood itself. Also, when you apply the clear coat coat, you will have an application window, possibly as short as a few minutes to maybe 24 hours. Not adhering to that will allow the clear solvents to degrade the base. Then there is that possibility that you have some paint that is degraded ........

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post #5 of 12 (permalink) Old 03-10-2013, 09:20 AM
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You are buffing the whole thing with 6 to 10k grit polish? Once the lacquer is on it, it might as well be a car.

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post #6 of 12 (permalink) Old 03-10-2013, 10:24 AM
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What kind of wood. That can make a huge difference at times.

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post #7 of 12 (permalink) Old 03-10-2013, 11:28 AM
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Aerosol - if you using spray cans from a big box store, the problem may be that it's really not lacquer. Look at the label and if the solvent for cleanup is anything other than lacquer thinner, the product is not lacquer. I just saw a "Lacquer" label that recommended mineral spirits or Xylol for cleanup which means it's oil based, even though it flashes quickly. Clean your piece up by sanding or scrubbing with a solvent, apply a couple of wet coats of dewaxed shellac to seal out any residue from the previous finishes, when dry (about 20 mins or so) sand with 400 grit, tack totally clean, apply lacquer sealer, sand, then black, sand and clear. Lacquer "bites" into the previous coat, so it should never peel off. If you are using spray cans, a small investment for a siphon gun and a small air compressor will make your life much easier.

If you get "blush" (moisture entrapment), add one drop of castor oil (sometimes two are necessary) to your spray cup, stir thoroughly. This will act as a "blush retarder" causing the lacquer thinner to flash off a little slower. Castor oil is much cheaper than commercial blush retarder. By causing the thinner to evaporate slower, the residual moisture will be evaporated also. You may need it in the black coat, but if you apply the clear within a short period, you should be OK.

Last edited by randyb01; 03-10-2013 at 12:13 PM.
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post #8 of 12 (permalink) Old 03-10-2013, 12:34 PM Thread Starter
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JOAT, the wood is poplar.
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post #9 of 12 (permalink) Old 03-10-2013, 12:53 PM
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Hi Tom. Many good suggestions above. Another is the possibility that you are sanding through your sealer, in places; giving you the randon opportunity for the lacquer to penetrate. I have found that going to 220 grit on the wood gives me a good base. I use 320 or 400 on the sealing layer, and only sand enough to remove the very top 'hairs and sniglets'. Tim
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post #10 of 12 (permalink) Old 03-10-2013, 02:40 PM
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Quote:
Originally Posted by randyb01 View Post
Aerosol - if you using spray cans from a big box store, the problem may be that it's really not lacquer. Look at the label and if the solvent for cleanup is anything other than lacquer thinner, the product is not lacquer. I just saw a "Lacquer" label that recommended mineral spirits or Xylol for cleanup which means it's oil based, even though it flashes quickly. Clean your piece up by sanding or scrubbing with a solvent, apply a couple of wet coats of dewaxed shellac to seal out any residue from the previous finishes, when dry (about 20 mins or so) sand with 400 grit, tack totally clean, apply lacquer sealer, sand, then black, sand and clear. Lacquer "bites" into the previous coat, so it should never peel off. If you are using spray cans, a small investment for a siphon gun and a small air compressor will make your life much easier.

If you get "blush" (moisture entrapment), add one drop of castor oil (sometimes two are necessary) to your spray cup, stir thoroughly. This will act as a "blush retarder" causing the lacquer thinner to flash off a little slower. Castor oil is much cheaper than commercial blush retarder. By causing the thinner to evaporate slower, the residual moisture will be evaporated also. You may need it in the black coat, but if you apply the clear within a short period, you should be OK.
NOTE* If you use caster oil in a spray gun, you are committed to use it every time from then on as it will cause fish eyes thereafter in use with other paints. ALSO, caster oil will forever attract more dust than normal on your finished piece. That's a FACT!!

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