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FDP Forum / Guitar Mods, Repairs, and Projects / CA Glue Finish Repair Question

BrentD
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Michigan

Poured Volume
Mar 7th, 2019 01:16 PM   Edit   Profile  

I have a Strat where the finish is cracking along the skunk stripe. The wood appears not to be separating - I think it's just differing expansion rates between the walnut and maple on a guitar that has seen some abuse.

I would like to fill in the chipped parts and strengthen the cracks with thin CA glue (as Peegoo and others have recommended here before).

Do I have to layer the glue to build it up over the edges of the chips, or do I let it seep in but put enough on there that it build up beyond flush on the first application?

Peegoo
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Just beyond Mars

there's a world of fools
Mar 7th, 2019 01:36 PM   Edit   Profile  

The first thing to do is relax the strings all the way and then relax the truss rod (loosen it until the nut turns easily).

Next, make sure to use water-thin CA, because the thicker stuff won't wick into the crack via capillary action like the thin stuff does.

Work under a very bright overhead light and use a magnifying visor if necessary; you have to lay a very thin line of CA along the crack, and then observe it to see if it gets sucked in. You can see this happening by orienting the work so you can watch the reflection of the overhead light in the liquid CA. This technique is usually called 'working into the light.'

Have paper towels on hand. If you drip any CA anywhere it doesn't belong, immediately wipe it away with a single swipe of a paper towel. More than one swipe will just smear it around and make things way worse.

Usually the CA will be drawn in along most of the crack. If so, carefully apply another thin stripe of CA over the areas that sink in. Do this no more than two or three times, and then let the CA set up for a few hours.

Repeat this process (two or three applications at a time with cure time between) until no more CA draws in.

Lastly, you scrape the excess CA from the wood using a razor blade. You don't slice the CA off, you drag the blade perpendicular to the wood and scrape it.

Follow that with block sanding with 600-grit and a few drops of water, then 1000-grit paper and water.

If you like a shiny neck, use the polishing compound (e.g., Meguire's, etc.) of your choice.

More info:

Some people mask off the crack with tape, but that can make things messy for beginners because sometimes you end up gluing the tape to the finish.

If you want to try this, 3M Scotch Tape is the best to use. The best approach with the Scotch Tape is to lay on a stripe of CA on the crack, give it about 30 seconds to draw in, and then quickly wipe off the excess in one move (along the length of the crack) with a paper towel.

(This message was last edited by Peegoo at 03:38 PM, Mar 7th, 2019)

BrentD
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Michigan

Poured Volume
Mar 7th, 2019 02:02 PM   Edit   Profile  

Thanks, the procedural details really help! There are places where no chips have come out but there are clearly cracks that look like this (but less than a half-millimeter in lenght): ///////////. I assume with careful enough application that thin CA glue will wick into these as well. Is that right?

Peegoo
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Just beyond Mars

there's a world of fools
Mar 7th, 2019 02:30 PM   Edit   Profile  

Not always. It's best to try first. If no results, use the tip of an X-Acto knife to flake off the little finish chips, and then fill those with the CA.

BrentD
Contributing Member
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Michigan

Poured Volume
Mar 7th, 2019 02:38 PM   Edit   Profile  

Sorry for so many questions, but I have one more. If I slack the strings and loosen the truss rod, is there a risk that the CA glue will crumble under stress when the guitar is set up again? What makes slacking objectively better than doing the repair under normal tension?

Peegoo
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Just beyond Mars

there's a world of fools
Mar 7th, 2019 06:03 PM   Edit   Profile  

It allows the wood to relax. You certainly could leave string tension and truss rod tension on the neck if you like, but I always relax it so I'm not gluing wood together in a pre-stressed state.

The CA won't crack or crumble. There's not enough flex in the neck for that to occur.

twangdoodles

michigan usa

Mar 8th, 2019 05:17 AM   Edit   Profile  

One thing not mentioned: CA and lacquer don't get along. I assume you're dealing with urethane but thought I'd mention it.

Also, paste wax can be used to contain the CA around the working area.

Therealfrogman
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Pueblo, Co

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Mar 8th, 2019 05:32 AM   Edit   Profile  

I have been following this because I want to fix a small hole on a lacquer guitar using CA. I understood the opposite about them getting along but as usual I have done no other research of my own. The hardness of CA and the softness of lacquer being the issue?

My plan was to do touch up with lacquer nail polish so I do not need the Ca to act as a top coat. Sorry for the thread jack but the technical know how is too much to pass on ;)

twangdoodles

michigan usa

Mar 8th, 2019 06:26 AM   Edit   Profile  

CA will soften the lacquer and possibly leave you with a big mess to clean up. It may be the case that it'll turn the lacquer whitish as well, but I may be confusing that with what sometimes happens when using accelerator.
Yeah, if you have a lacquer guitar then use lacquer to fix it.

wrnchbndr
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Mar 8th, 2019 07:43 AM   Edit   Profile  

I have observed that letting a CA repair like this sit for a few days results in a better result. Especially if you're dealing with lacquer, as mentioned, this can go south. The components of CA can soften the structure of the finish -- both the top finish and the undercoat and primers. Although the CA hardens quickish, the surrounding finish becomes soft even gummy. If you try to cut back the CA with sandpaper early, the finish will not cut at the same rate when it is soft and you end up chasing your tail for cosmetic results that just won't happen. A few days of curing and both the CA and the finish seem to be harder and the process of leveling is much more straight forward with far better results.

Peegoo
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Just beyond Mars

there's a world of fools
Mar 8th, 2019 08:32 AM   Edit   Profile  

Also, don't use accelerator because it can cause the CA to turn opaque (bad) or create bubbles in it (really bad).

BrentD
Contributing Member
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Michigan

Poured Volume
Mar 8th, 2019 12:28 PM   Edit   Profile  

Thanks for all the extra info. It's a urethane finish on there - an early Highway 1 Strat with an acrylic body finish but a poly-coated neck. I watched a good video from StewMac where Dan E. does the job. He seemed to build it up in layers and the thin CA sets quickly.

Does brand matter? I see the Hot Stuff branded glue looks like it's preferred by some, but it's only available an hour from here. If any thin CA glue will work, I'll just head on down to the big box home improvement store for a fresh tube.


BrentD
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Michigan

Poured Volume
Mar 8th, 2019 01:04 PM   Edit   Profile  

wrnchbndr, does your recommendation for extra cure time apply only to lacquer repairs, or would the same be true for a urethane finish?

wrnchbndr
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New Jersey

I'm back with the otters again
Mar 9th, 2019 08:34 AM   Edit   Profile  

Both

Te 52

Laws of Physics

strictly enforced
Mar 9th, 2019 03:10 PM   Edit   Profile  

Cure time for CA adhesives depends on humidity, temperature, and thickness of the application. Using a thick application of high viscosity CA doesn't always make for a shorter total repair time.

Reason is, CA cures when exposed to moisture vapor in the air, so it forms a thin cured skin almost immediately. But that skin retards the cure of the CA deeper inside the blob, and the thicker the blob, the longer the cure process takes.

Having said that, even a very thick application will eventually cure completely.

(This message was last edited by Te 52 at 05:11 PM, Mar 9th, 2019)

mojodelic

I love guitars

and things that fly
Mar 29th, 2019 11:26 AM   Edit   Profile  

Piggybacking on this thread- can CA be used to drop-fill a ding in a PRS? The sales stuff they put out says the finish isn't exactly nitro or poly, but something in between.

Peegoo
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Just beyond Mars

there's a world of fools
Mar 29th, 2019 11:44 AM   Edit   Profile  

Howdy Pat!

Yes, it works great on PRS finishes; I've used it on them with good results.

Don't use accelerator; let the CA cure on its own, and it will guarantee a nice clear drop fill.

mojodelic

I love guitars

and things that fly
Mar 29th, 2019 12:14 PM   Edit   Profile  

Thanks Geno!

FDP Forum / Guitar Mods, Repairs, and Projects / CA Glue Finish Repair Question




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