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Well yesterday I finally dove in and glued on my neck. I'm using a mortise and tenon joint and I glued the fretboard extension down with hot hide glue. It was a bit stressful as I haven't used hot hide glue much but everything went tickety-boo. I set the guitar aside to dry overnight while I dreamt of making beautiful guitars that the masses wanted to buy.

In the morning I got up, removed my clamps and cauls and found this! For about 5 minutes I sounded like the father on A Christmas Story when he goes downstairs to fix the furnace. Lol.



I've had a good close look and it appears that the crack is only in the lacquer of the guitar. Although it appears to follow a grain line, the wood is still intact. In the photo you can see where the crack at the top goes on an angle and it appears to only be a lacquer crack. I'm guessing that I tightened one of my clamps down a bit too much, flexing the wood and cracking the lacquer.

So, before I even remotely attempt a repair on this, I wanted to get some input from you guys on how to properly fix this. I've watched a few videos, Robbie O'Brien's included, where CA glue is used to wick into a crack to repair it. But these videos show a repair for a crack that has gone through the wood. How do you repair a crack in what appears to just be the lacquer?

Here's my educated guess : sand the area, use a fine brush and apply fresh lacquer to the crack. Allow to dry, sand and reapply if insufficient lacquer. Once sanded level, rebuff and marvel at my repair abilities? Am I even close or right church, wrong pew?

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Rob Flindall
Flindall Guitars
http://www.flindallguitars.com
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Mask off the area around the scar. Find a toothpick and bit on the end till you fray the wood a bit (but don't slobber on it). Use that to apply some cellosolve or lacquer retarder to amalgamate the scar. A little dab does it. Then drop fill with nitro a little bit at a time till the fill is proud of the rest of the finish. This may take quite a few fills. Don't touch the guitar, well at least not the affected area, for 30 days at least (the longer the better here). Then scrap the filled area down with a razor blade scraper with tape on the outer edges, block sand flush, sand the area up to your buffing grit, buff, and then marvel at your work.

A CA fill can be faster, but assuming you are using nitro the results are generally less predictable than using nitro to repair. Fixing a CA fill gone wrong - no fun.

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Aaron Craig

Thanks for the reply. Another 30 days of waiting.... Shoot. I've never heard of cellosolve before. I googled it to try and find a source to purchase it from, but I don't think I need 50 gallons of it from India. Lol. Can you point me in the right direction on where to purchase some of this from?

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Rob Flindall
Flindall Guitars
http://www.flindallguitars.com
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What he said....

If it indeed is a hairline crack in the laquer, you can drop thin laquer onto the it and it should wick fully into the crack provided you haven't wicked any other liquid in already. Let it dry 24 hours, then razor scrape it flush, sand with 1000 grit then 1500 (on a hard block) then buff shiny! For a crack that size I use a 1 inch square wood block with the edge rounded so as not to scratch the wood (not a rounded bottom!)

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Old growth, shmold growth!

A bit of proud lacquer doesn't stop you playing it, but it might stop you delivering it. If you flatten and buff too early, you'll just have to do it again if you want it to be invisible down the track.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Cellosolve is a brand name, try looking for butyl acetate. Or go to your auto body supplier and by some retarder.

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

I'm no doctor, but adding this stuff to your drinks seems like a fantastic idea! Talk about getting a buzz!! YEEHAW!!!!

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http://www.CostaGuitars.com
PMoMC

WHATEVER YOU DO DO NOT BUFF IT FOR AT LEAST 30 DAYS! Just putting that little drop fill in will soften the new lacquer, which is what you want so it amalgamates itself together. It's going to shrink again and because of this so you need to build it up as previously described and let it sit as long as you can. Longer is better here because the butyl acetate a/k/a reducer, is going to act as a plasticizer and soften the surrounding finish all the while the finish beyond the immediate repair area will continue to cure from your last spray session. Grind the corners off a single edge razor, tape along both sides of the repair and GENTLY scrape the finish down, then block sand, and feather the sanding outward so you don't end up with a divot. Use the 3M 233 green masking tape, to mask, but do not leave it on longer than a few minutes as it and any other tape will eat lacquer or even young polyester. Use the highest grit you can get away with, such as 800 and go up from there, and buff it out.

Longer is better, yes, especially with a ding or missing laquer where you're replacing a substantial amount of material, but I've done this with hairline cracks after 24 hours with no ill effects, with thinned laquer. Laquer thinner has butyl actate in it, and the addition of nitrocellulose solids helps reduce the shrinkage effect.

Depends on how much of a hurry you are in.

But I agree, "hurry" and "luthiery" typically don't go together.

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Old growth, shmold growth!

I just got back from a trip to the local autobody supply shop and found a couple of products that may possibly filt the bill, but I left them on the shelf because I wasn't sure of their cocktail. One is a medium reducer and the other is a universal lacquer thinner, both made by Nason.

Here's what's in them :
Nason 481-06 Universal lacquer thinner
- butyl acetate
- heptane
- propylene glycol monoethyl ether acetate
- toluene
- isopropyl alcohol
- acetone
- ethylene glycol monobutyl ether

Nason Ful-Base 441-21 medium reducer
- butyl acetate
- acetone
- toluene
- heptane
- ethylbenzene
- xylene
- ethyl 3-ethoxy propionate
- n-hexane

The main differences in the above are in bold. If neither of these fit the bill, I'll place an order from thechemistrystore and wait for it to come in.

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Rob Flindall
Flindall Guitars
http://www.flindallguitars.com
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I just use Behlan's lacquer retarder. The quart a have will probably outlive me.

http://m.woodcraft.com/product/2005524/ ... quart.aspx

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Aaron Craig

That would be a nice and easy answer, but this dummy didn't pick any up last time I was in the US and unfortunately I can't get it shipped to me. Lol.

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Rob Flindall
Flindall Guitars
http://www.flindallguitars.com
https://www.facebook.com/FlindallGuitars

Thanks for the input everyone. I'll pick up the lacquer thinner tomorrow and give this go. I better get on it asap as I have another 30 days to wait!

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Rob Flindall
Flindall Guitars
http://www.flindallguitars.com
https://www.facebook.com/FlindallGuitars

The reason for my insistence on waiting longer is that there is so much variability with lacquer formulations that suggesting 24 hours or a week is just not prudent. McFaddens notoriously has a some of the highest content of plasticizers of any of the lacquers and would be more susceptible to sinkage than some others like Valspar, or perhaps Cardinal. The other problem is that assuming that you sprayed judiciously before the repair, then there isn't a lot of lacquer to allow for additional sanding and buffing. If you don't wait long enough, and it comes back because the repair starts showing, then you might be out of luck and end up having to pull the neck and locally spray the whole area. Just not worth it.

You can still do the set up while waiting for that lacquer to cure out the 30 days. Leave it for 2-3 days after you've done the fill and you'll be fine to handle to guitar, set it up & play it too.

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"There's really no wrong way, as long as the results are what's desired." Charles Fox

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just to be sure that the crack is not in the wood, wet with naphta and observe the inside of the "crack" with a mirror. the naphta will seep through and wet the inside if the crack goes through the wood. no telltale wet line you're set to repair the finish.

But.... What caused the crack?