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Lacquer finishing problems

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Forum topic by NoSpace posted 01-15-2018 01:25 AM 599 views 0 times favorited 9 replies Add to Favorites Watch
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NoSpace

127 posts in 1361 days


01-15-2018 01:25 AM

I have a maple and mahogany chessboard I’m finishing with lacquer—never done it before and therefore, don’t know what to expect.

I filled with aquacoat, sanded, and then put on 5 or 6 coats of spray lacquer on waiting 1/2 hour in between each coat just like the can said. I waited a couple weeks to let it harden.

I think one of my issues here is I don’t know at what point i’ve sanded enough at one grit and time to move to the next, I have a feeling I may not have sanded with a coarse enough grit BUT; here’s what I did:

RO sander with 220 until an even coat of white powder built up. I have a halogen light on it and looks good. then, lacking other grits, I wet sanded 400; 1000; 1500.

the little problem:

Just like sanding poly, it looks awesome when it’s wet, but then as it dries it turns milky. With poly—what I’ve always used—a quick thin coat makes it beautiful again. But you don’t do lacquer that way, my assumption being that it starts to shine up as it gets more smooth, but this isn’t happening. in direct halogen light it look great, but milky in normal daylight.

the big problem:

this project is a first for a lot of things, wet sanding, lacquer, grain filler, and I also bought rottenstone and pumice.
I decided to try the rottenstone out. the directions say use oil, so I use mineral oil and a cotton cloth. disaster. it appears the black stone powder found its way into tiny cracks and it looks like somebody shaved over it and left little black whiskers everywhere. And i cant get it out. tack cloth doesn’t work, sponge, light grit sanding, and even running the RO with 220 has removed maybe 60%, but it’s seeming like I’ll need to put 120 grit on and hope I don’t take off all the finish.

well, right now I’m stopping everything and getting advice from the pros first ; )


9 replies so far

View pintodeluxe's profile

pintodeluxe

5741 posts in 2934 days


#1 posted 01-15-2018 02:21 AM

Wow, I’m sorry you had so many problems with the lacquer finish. Sounds like it really went off the rails.

Are you spraying with an HVLP, or rattle cans? One big advantage with using your own sprayer is you can thin the lacquer so it will lay down flat and smooth.

Put the ROS away once you lacquer. It’s just way too aggressive for sanding your topcoats. Instead use a 1200-1500 grit soft sanding sponge to scuff sand each coat of lacquer. By the second or third coat it should sand smooth with very little effort.

Wet sand the final coat with water and the same grit sanding sponge.

Since the damage is already done, you need to strip it with 80 or 120 grit and work back up to 150, or perhaps 220. Throw away the tack cloth and get some cheese cloth from the hardware store. Use it to clean the lacquer dust after sanding each coat.

Don’t give up!

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View Rich's profile

Rich

3548 posts in 710 days


#2 posted 01-15-2018 04:24 AM

For small projects like that, I like the Mohawk products available in spray cans. They make a product called a heavy body sanding sealer that I start with. I use Mirka Mirlon total maroon non-woven pads between coats which are 360 grit and won’t clog. I move on to their high-solids pre-cat lacquer and the Mirka grey pads that are 1500 grit. After that, I use their pre-cat lacquer in the sheen that I think will suit the project. They have dead flat, flat, satin, semi gloss and gloss. The nice thing about the whole system is that it is all solvent based and they work beautifully together.

Once I get down to the final coat or two, I like to use a thin scraper, 0.010 to 0.015” thick. It’s squared off like a cabinet scraper, but you don’t turn a burr with the burnisher, you just leave it square. It will flatten any high spots you might have gotten with the spraying and generally one or two very light coats will smooth the surface to a flawless finish.

The scraper is great for leveling any sags on vertical surfaces too. I like to use it instead of abrasives because it cuts any drip or sag flush with the rest of the finish, unlike abrasives which remove the surrounding finish along with the sag. Again, a light spray or two is all it takes to complete the finish.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

View OSU55's profile

OSU55

1835 posts in 2110 days


#3 posted 01-15-2018 02:49 PM

Sounds like you did not get a complete fill (can be difficult) or the rottenstone would not have cracks to stick in. I use auto type clear coat finishing products after the final sanding. I prefer Macguairs products. Up until the rottenstone you were in good shape. Replace it with paint finishing products. Also microfober towels are great for removing dust.

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NoSpace

127 posts in 1361 days


#4 posted 01-15-2018 06:04 PM

OSU55, up to the rottenstone, was it okay that from a side view in daylight the “gloss” sheen looked dull? does that come out with polishing, or something more fundamentally wrong, like, surface uneven.

I’ll admit i didn’t sand between coats, because the lacquer can instructions didn’t say i should. ; )

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NoSpace

127 posts in 1361 days


#5 posted 01-21-2018 02:45 AM

let it sit for a few days. sanded until the black was nearly gone and figured the lowest points should leave enough finish on i could try and salvage it (6 unthinned coats from a can). practical limitations to stripping it down and doing over, one of them being my shop is dual purpose as a secondary office and I have to say, I have never used any finish or any chemical for anything for that matter, that smells worse than lacquer; days before it was right again.

under proper lighting, just used common sense and sanded lighter and lighter making even coats of dust until it was very smooth. Yeah, still looked “dull” but the Meguiars 7 polish did take care of that. Next time it will be better, but the end result was as good or better than poly and there are a couple other flaws more significant than the finish so time to shut this one down.

http://lumberjocks.com/projects/359097

View Dark_Lightning's profile

Dark_Lightning

3225 posts in 3229 days


#6 posted 01-21-2018 04:45 AM

I would never dry sand beyond 400 for a lacquer finish, personally. Lacquer will melt into the previous coats and level them off, when applied properly. Dulling usually comes from the finish flashing off too quickly. Not to be confused with “blushing”, which is caused by humidity- a problem I’ve not encountered here in southern California, generally.

It occurs to me- are you using a nitrocellulose lacquer, or a water-based California-accepted “lacquer”? If you are using a lacquer almost anywhere else, it should work just fine, but that Cali stuff can give you grief, sometimes.

-- Random Orbital Nailer

View Fred Hargis's profile

Fred Hargis

5072 posts in 2614 days


#7 posted 01-21-2018 01:07 PM


It occurs to me- are you using a nitrocellulose lacquer, or a water-based California-accepted “lacquer”? If you are using a lacquer almost anywhere else, it should work just fine, but that Cali stuff can give you grief, sometimes.

- Dark_Lightning

Very good question, the approach would be different for the waterborne.

-- Our village hasn't lost it's idiot, he was elected to congress.

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NoSpace

127 posts in 1361 days


#8 posted 01-21-2018 03:50 PM

Deft clear gloss, 4$ at home depot. I doubt anything water based could smell like this, it has lead warnings so…

It is sold in California.

“Lacquer will melt into the previous coats and level them off, when applied properly”

right, which is why i didn’t sand between coats. while rottenstone finding tiny imperfections to fall into is interesting, and may serve as a litmus test for a perfect application, i have to wonder if it’s a road less traveled. wondering if the can instructions don’t anticipate such an exotic approach, and what I had was fine for what it was.

not sure what you mean by “flashing off”. if you mean sanding too aggressively, will need some practice. the sides were untouched until last night and went much better, ended in more of a satin finish after sanding 1500. If I do this again I’ll do it the same up until sanding, get it in the right light and go very slowly. My gut instinct is the car polish OSU55 recommended covers up half-assed workmanship pretty well. ; )

At some point I’ll try Rich’s method with the scraper, evening up sags to get a perfectly even surface seems to be the way to go. But, my next stop is General Finishes poly, which gets such great reviews, and if it has a less plastic look than what I use, I might hold off on lacquer because of the odor.

View OSU55's profile

OSU55

1835 posts in 2110 days


#9 posted 01-21-2018 08:31 PM

“Flashing off” means the solvents in the finish evaporate or flash off. Nitro lacquer is an “evaporative” finish. Seems you did ok with fill and finish application, you started going awry with the “rub out” process. You can find various methods. Here’s a short description of my approach.

For a filled finish I dont sand between coats of lacquer unless I get a bad run, blemish, or roughness. Always use a backer pad for sanding. If so, I use a flat backer if flat with 400-600 paper and a scraper as mentioned. Easy does it, lacquer burns in, a real plus. After all planned coats let dry a couple of days. Lightly sand with 600 and evaluate for level. If you can sand out imperfections, stop and let it cure for as long as possible (several weeks – it is difficult tp prevent telegraphing – wood grain image startion to appear in a prviously mirror flat surface from the finish continuing to cure and shrink). I usually start with 600 and wet sand, and progress through 800, 1000, 1200. Goes pretty quick, but evaluate a dry surface at each grit. Then the auto finish polishes are used. A light cutter, then swirl remover, then the final polish. I use a flex dual action polisher.

Drop filling works pretty good with lacquer. If you find pinholes or small low spots drop lacquer straight into and let dry. Scrape and sand flat, then recoat the entire surface. Repeat until the surface is perfect. Best done before starting the rubout.

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