Lacquer Thickness Confusion

The Achilles' Heel of Luthiery
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Stray Feathers
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Joined: Sun Sep 08, 2013 11:39 pm
Location: Ladysmith, BC

Lacquer Thickness Confusion

Post by Stray Feathers »

I'm currently spraying two guitars and this time I remembered (a little late) to put small squares of cereal box cardboard on the bridge mask, with D/S tape, to try to better assess how much lacquer I am putting on. I am confused after reading what thickness I should be aiming for, as some threads are not clear whether the numbers are including or not including card thickness. The cardboard before finishing was .0165. I did not put the test cards on until after I had finished the sealer coats and pore filler, so that layer is not counted. After three thinned coats (50/50) of lacquer, I think I had .0015 of finish, so .018 including the card. I've now done three consecutive days of three "build" coats (65/35) each, drying overnight each time, with one 400-grit scuff sanding on one of those days. I am now at .0185 thickness of card plus finish, or, by calculation, .002 of finish. That does not seem much. Does this make sense? Or, what thickness of finish only should I be going for at this point, before curing? Bruce W.
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tippie53
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Re: Lacquer Thickness Confusion

Post by tippie53 »

don't think that much I know I used to I found a better mix
you need to look at nitro as a 2 step process
.012 to .016 on the first coats 6 to 8 coats day one
no need to think more than 25% I am doing about 20% and will add a touch of retarder on high humidity days

Once you do the first 6 to 8 coats let cure 14 day

now use 400 grit to level sand . Yes 400
Once leveled do 3 coats 25% thinned allow 14 days to cure

this you will level off starting at 1000 1200 2000 2500 3000
buff and polish

TAKE THE CARDBOARD OFF. mask that area if you want and place 3 small pieces of tape pull that to measure build

I hate doing assembled guitars it makes doing the neck heel difficult and the area at the heel will eventually lift.
John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
president of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com
Stray Feathers
Posts: 677
Joined: Sun Sep 08, 2013 11:39 pm
Location: Ladysmith, BC

Re: Lacquer Thickness Confusion

Post by Stray Feathers »

Thanks John - but I am still confused - if you say I should have up to .016" lacquer after 6-8 coats, that is the thickness of the cereal box cardboard I am using for test squares. So when I measure these test squares I should have a total thickness of roughly .032"? If so, I have a long way to go as I am only at .020" now after nine coats. For the record, I am using test squares because many have said they used business cards in the soundhole, and also I thought they would be easier to remove and measure than masking tape. They come away from the D/S tape cleanly with no adhesive to get in the way of measuring. But I am willing to try masking tape. I'll think about it for a while . . .
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