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 ARCHIVED TOPIC: Lacquer cure time


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dickinnorwich - Posted - 01/15/2008:  10:41:07


Guys and Gals:
Now I need some finishing help/advice from you folks:
How long should one let acrylic lacquer from a spray can cure before it is rubbed out? And, secondarily, is the cure time reduced appreciably if the piece is placed in a warm-dry climate, say, under heat lamps?


beegee - Posted - 01/15/2008:  10:49:45


It depends. I like to wait 24-36 hours before sanding and rubbing. Ultra-violet may do better than heat lamps. If the surface cures before the solvents flash out, you may get blushing or crazing. Resist the temptation to rush.

______________________________

ne credes laudatoribus tuis

wfawley - Posted - 01/15/2008:  11:02:14


Dick....

The best way to accelerate drying time of lacquer is not by heat....but by keeping air moving across it. Lacquer fumes lingering about the finish tend to keep the finish soft. Use your nose to figure out when it's cured enough to hard buff. When most of the smell is gone...it's ready. I would imagine at least a week with most of the aerosol stuff...possibly 2 weeks

Wyatt

"I'm hairy noon and nighty night night"

dickinnorwich - Posted - 01/15/2008:  11:07:29


Bob:
I'm not talking about rubbing between coats, I'm talking about the final rub out.
Usually, I wait about a week before I start the rub out process with compound and polish. I put the neck or resonator aside, on a shelf in the house, where I'm reasonably certain it is dry, warm and safe from curious little hands. But I have found that after I use the polish, the lacquer softens and if I'm not careful, I can leave deep fingerprints in the finish. To avoid this, I find it is best after I polish to put the piece aside again for 3-4 days and let it reharden.
So my question is, am I starting the final rub out process too soon or is this simply the nature of the beast?

Bill Rogers - Posted - 01/15/2008:  11:15:22


When I shot acrylic in Hideo Kamimoto's shop way back when, we let it cure three weeks before final rubout. It is, indeed, "the nature of the beast."

Bill

dhergert - Posted - 01/15/2008:  11:48:10


Hey guys, I've not sprayed since the mid-80s and was still using nitro at that time. We'd put fish-eye remover and accellerators into it sometimes. But if we wanted a good job we planned for a month. Back then you couldn't get good spray cans of the quality we wanted, or if you could, we didn't know it then.

Do spray can lacquer finishes come out as good as the old nitrocellulose lacquer finishes did? Is their absolute drying time better?

Best,

-- Don
http://home.att.net/~dhergert
http://mysite.verizon.net/don_hergert

"If you must use your banjo as a snow shovel, do so:
only don't wonder if it sounds dull afterwards."
-- S.S. Stewart catalog, 1896.

dickinnorwich - Posted - 01/15/2008:  12:07:10


Don:
I've been using clear acrylic lacquer for about 18 years now. I used to buy it by the quart from my local auto paint supplier and spray it with a small touch-up gun. But I find that for small jobs, like necks, acrylic lacquer in spray cans is more than adequate. Once it hardens, it's HARD!
The question I have for Bill Rogers is this: Do you recall if even after letting it cure for 3 weeks, the lacquer still softened in the final polishing stage and required additional curing?

Banjophobic - Posted - 01/15/2008:  12:36:05


Yes, Acrylic is a different animal than Nitro. I dont use it on instruments becouse of its brittle nature when cured and long cure times. Follow the patients rule and let it dry about a month. Are you mixing reactants with it,i.e blush erasers,fisheye remover,ete in the lacquer? They do their work by slowing drying time/improving flowout. If you use these then expect even longer dry times.

dickinnorwich - Posted - 01/15/2008:  14:25:34


John:
I have not really had a problem with brittleness with the acrylic. And I haven't been adding anything to the lacquer to slow it down.
I think what's happening(?) is that there might be a chemical reaction to the lacquer from the compound and/or polish I'm using as it cuts through the initial surface layer(s) of lacquer. I say this because I don't seem to get the softening of the lacquer with the initial (more aggressive) rub out with wet-dry paper.

fitch5string - Posted - 01/15/2008:  14:28:37


hey Dick, why dont you try the Colortone nitro lacquer from Stew Mac. It comes in spray cans and works great. I use it for small stuff and they have tinted lacquers now that are awesome. I let my lacquer cure for at least 3 weeks before level sanding and buffing.

Cliff Fitch
FITCH BANJOS
Hand-Crafted Professional Banjos
Banjo Repair, Set-up ,and Restoration
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And Authorized Recording King Dealer
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dickinnorwich - Posted - 01/15/2008:  14:36:38


Cliff:
Thanks for the tip. I did see the nitro spray can lacquer advertised in my last Stew-Mac catalogue, along with the tinting lacquer. That piqued my curiousity and I will include a few cans with my next order.

I should add that I'm a big Colortone fan and I use their stains exclusively, now. They're virtually bullet-proof and I've had great fun mixing up different color stains.


Edited by - dickinnorwich on 01/15/2008 14:39:37

stanger - Posted - 01/15/2008:  14:49:32


quote:
Originally posted by dickinnorwich

John:
I have not really had a problem with brittleness with the acrylic. And I haven't been adding anything to the lacquer to slow it down.
I think what's happening(?) is that there might be a chemical reaction to the lacquer from the compound and/or polish I'm using as it cuts through the initial surface layer(s) of lacquer. I say this because I don't seem to get the softening of the lacquer with the initial (more aggressive) rub out with wet-dry paper.





Hi, John...
Acrylic lacquer dries harder than nitro, but still requires about as long a curing period. I think you'retryig the buffing & polish too soon. Both heat the finish much more than the final sanding rub-out, because the grits used are much finer and produce more friction when worked.

As so many folks posted, the longer the better. 2 weeks should work just fine, and in a pinch 10 days may work, but any sooner is chancy, because the lacquer hasn't had time to fully meld. Lacquer cures from the bottom up. The fume odor tends to fade away long before the bottom coats are fully dry. (You can still smell 'em, though... you just have to put your nose real close to the wood.)

If you were buffing aggressively, you went through the top coats into the softer ones below.

You can pull the shine with the buffer, but I like to step the final sanding to fine grits and keep the buffing to a minimum; I found I lose less coat thickness this way. I start with 400 to level sand, then go to 600, 800, 1000 and 1200. Then I spend about 5-10 minutes at most with the buffer. Everything past 800 is just sanding increasingly lighter scratches- it takes longer, but I get a much deeper finish look and no burn-throughs.
regards,
Stanger

The pen is mightier than the pigs.

Bill Rogers - Posted - 01/15/2008:  15:49:23


Never remember the lacquer softening. I was doing mostly electrificated guitars, using colored lacquer.

Bill

dickinnorwich - Posted - 01/15/2008:  15:53:22


Hmmm.
O.K., so it's a minimum 2 week cure time rather than the week I was allowing. Good. Thanks for all the help. I appreciate it. I'll report back.



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