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Could someone give a short tutorial on drop filling using lacquer?

A friend brought over a guitar that had a crack in the solid spruce top. It happened about a month ago and the crack is clean with no dirt or polish in it. I can rub hide glue into the crack from the top and clamp bringing it together to dry.

My concern is that the glue will then be between the lacquer. Will that cause problems when drop filling? I mixed up 50% lacq and 50% lacq thinner hoping this is how it's done, but I don't want to touch it until know for sure.

Once I drop lacqr in the crack how do you make the crack invisible.

I really appreciate the help,
Chuck

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"After forty-nine years of violin building, I have decided that the search for a varnish is similar to the fox hunt. The fun is in the hunt."
Jack Batts Maker and Repairer of Fine Violins

Chuck, is the top lacquer? Make sure. I would repair the crack and make sure it pulls completely closed. Consider a cleat under the top if its in a bad spot or is a long crack. Then I would sand the area with 600 or 800 grit to make sure the repair is level. You can then tape off and spray or drop fill depending on how much you have sanded. Once dried, you will wet sand with a block until the repaired finish is level with the old finish. The buff/polish to match.

Some have done simular repairs with CA as the finish. It works well too if your trying to fill only the area of the crack. But unless the crack is perfectly level, I think you will see signs. That is why I suggest sanding the area flat with 600-800 first.

I am sure others will chime in, but this is how I have done these repairs in the past.

J

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Joe

BTW: I drop fill without diluting the lacquer. Lacquer is thin and self levels. If you thin it to much it might make a mess of the original finish. It should melt into the old finish, but to much thinner could just melt the old lacquer...

JD

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Joe

I drop fill with THICKENED lacquer .. not thinned ... why .. because i think too much thinner will melt the surrounding area too much, and cause it to shrink leaving a witness line - if you do this, you will need to make sure and over fill the area. The other thing is this - TIME - you will need o leave the drop filled area for a while, like months, as is, then flat sand and buff. again, the area will have newer softer lacquer on it, surrounded by older harder lacquer, a guaranteed area that if flat sanded and buffed too soon will shrink and leave a divot. If done after a wekk or two, it may look fine the day you do it, but a couple weeks later it will have shrunk into the repair.

A student had a guitar he made wtih me chipped when a strat was knocked into the edge and top - upper bout, lower side. We dropped filled it and left it for about four months (the finish was about a year old) Then we flat sanded and buffed out - you cant find it.

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

My advice (not the advice you asked for):

Don't try drop filling a tight crack.

Begin any cosmetic work on a top crack by lowering the client's expectations. Tell them invisibility is not possible. Get their expectations down so you have a chance of exceeding them.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

I agree with Howard about the invisibility stuff. That just won't happen on spruce. And drop filling a tight crack with lacquer is not going to do much other than build up above the surface. However, thin CA glue can SOMETIMES seep into a tight finish crack and make it almost invisible. Things that can go wrong with this are:

1) bubbles left in the repair,
2) insufficient penetration of the glue, or
3) a bead of glue getting away from you, running across the finish leaving a big scar.

Although a newbie here, but I've got 30+ years experience in antique/art restoration and have done a lot of repairs on all kinds of wood objects. I can chime in that getting hide glue in the crack is probably the last thing you want to do. It will probably show forever and make the crack more visible.

Also, retouching lacquer can be dicey and you want to avoid too wet, so I agree with the thickened lacquer for drop fill or razor fed touchup. I've used a razor blades and dental tools to guide small amounts of finish to an accurate spot/line. Dip an edge into the lacquer and line it up with your spot to fix and lightly let the lacquer touch the surface. A slightly bulged line will dry pretty darn near flat. I use a jeweler's bi-ocular magnifier to get a good sharp look at what I'm doing while I'm doing it. Nothing beats seeing it 2-3x as large, as one will normally see, while making the repair. If you are really careful and have steady hands, you may not have to do anything to the finish once it's dry. Maybe a light buff with 1500 or 2000 wet paper and a bit of polish.

To start get a 10x loop and look at the crack under magnification and good light. See what the profile of the finish is at the edge of the crack to determine how much you'll need to fuss with it. While you have that loop out , look at the condition of the finish as a whole. If you start sanding and buffing you may need to do the entire surface to match it up. Be sure this is what the owner wants.

Perhaps the simplest fix is to use CA to seal and fix the crack. Even clamped a thin CA will seep into the crack and seal it. Of course you have to beware of CA wood discoloration effects.

I also agree, make it clear that once broken rarely does it come together and look perfect again. Promise less, deliver more. Thus a happy client.

My 2+ cents...

Joe

Howard, that's some good advise. Thank you.

I can reach the crack from inside the guitar, so I'll open the crack and rub some hide glue in it and clamp it tight and try the drop fill with thick lacquer and buff out in a few months.

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"After forty-nine years of violin building, I have decided that the search for a varnish is similar to the fox hunt. The fun is in the hunt."
Jack Batts Maker and Repairer of Fine Violins

Chuck, I have no idea how much repair experience you have (perhaps way more than me), so please forgive me if I'm only saying stuff you already know...

The key thing is to make sure the crack is closed up tight before putting any glue in. Humidify the guitar until the crack closes up tight on its own. The clamping you'll do after working glue (I'd use LMI white) into the crack is to make it flat, not to squeeze it together. Put thick, flat cauls above and below the crack (the caul on the inside will likely need to be custom made with cutouts for braces) and clamp it flat with deep throat clamps through the soundhole. With the crack closed up before gluing, and clamped flat while gluing, it will look pretty good - the crack line will still show, but there will be no gap in the finish to fill. To the best of my knowledge, most repair people would consider the job done at that point (after cleating the crack if deemed necessary) and leave the finish alone. If you still want to try to touch up the finish at that point, to make the line less visible, that's another matter, and potentially a can of worms.

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

If the finish is nitro keep CA away IMO .... I havent had any luck (and thats why I havent used it for this in years) fixing nitro with CA - the CA dries way harder than the nitro will be for years, if ever ... so once the nitro shrinks more in time (and it will), the line will be visible for sure. If its a polyester finish .. go for it - nitro wont stick all that well to it anyway. This is more for info for filling dings than cracks though ....

All that said .. I am with Howard - if the crack glues up tight, then leave it just like that. No need to get into more trouble

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

CelloSolve works good to weld cracks in Nitro.

Check out Frank Ford's technique. You even get pictures. http://www.frets.com/FRETSPages/Luthier/Technique/Finish/Lacquer/DropFill/dropfill.html The best advice is to allow enough time to let the lacquer shrink before you level or buff.

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Ken Franklin
clumsy yet persistent
https://www.kenfranklinukulele.com

http://www.frets.com/FRETSPages/Luthier/Technique/Finish/Lacquer/CheckRepair/checkfill.html

I owe credit to Frank Ford or Bill Moll for CelloSolve, don't remember who for sure.
Nelson

What I said before.

This is not amalgamating checks. Also, butyl cellosolve can permanently (for years, at least) soften lacquer.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

You're right, Howard.
I was off topic once again.
Nelson