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Good Morning, I just had one of mine come back with a small ding in the top and the owner had put in it. Didn't look like a big one to fill. It may have compressed the wood a little but didn't delaminate the finish. I filled it and shot a light coat of nitro over the fill with hopes it would help it all burn in better. I left it a week and levelled and buffed. You had to look pretty hard but there was a witness line around the drop fill. I didn't want to risk sanding through so I left it at that. The finish on this guitar would have been about 6 months old.

Any tips on not getting witness lines? On new builds I always shoot at least one full wet coat over any drop fills and that works but the finish is a lot fresher at that point.

Any help would be appreciated.

Cheers,
Danny

Hey Danny bro!

Instead of nitro thin CA without any accelerator.... and waiting for it to dry, repeating once or twice followed up by scraping near level with a single edged razor blade with the corners covered in scorch tape and then some wet sanding confined only to the the area of the ding followed by a buffing and the repair IME is invisible with no witness line.... Whew.... I should learn to write proper sentences....

Jescar, the fret wire people, have recently started selling other products and fret wire in small builder quantities too. We tried out their compound for removing scratches and shining up a finish and love the stuff. Just Friday I had a client instrument with a glue film on the top that would not remove with hot water or conventional polish but the Jescar compound took it right off in seconds and left a nice surface - good stuff. Might be a good solution to have around if more drop fills are in your future in so much as it eliminates the need to take the instrument to the throw it on the floor and wreck your day buffer...

Thanks Bud! I'll give it a try next time.

I've used similar methods to what Hesh describes with good success. I've learned not to buff the area too much as the CA is a lot harder than the nitro. To much buffing and the drop fill can stand out as the finish around it buffs away quicker. The customer may not notice, but I do. Be sure to allow the CA plenty of drying time, at least over night.

If I'm drop filling with lacquer I usually start by putting a drop of acetone on the ding I want to drop fill. That will soften up the surrounding finish and I find helps avoid witness marks. I drop fill with thick lacquer, a small jar of lac that I've let sit out for a bit to thicken up. I'll often put a coat (or drop) of regular thin lacquer over the thick fill which will also help the new finish to melt into the original. To me the biggest factor in avoiding witness marks is letting the lacquer drop fill fully cure. This can take a few weeks, just like a new finish. Since I don't usually have 3-4 weeks to let a repair sit I've found different methods to speed up the cure time, like having a fan blowing on the guitar or a hair dryer set to low blowing on the area to cure. I'm carful to position the hair dryer at the proper distance so that it is only warm air blowing on the drop fill, not hot. I check on it regularly never leave it unattended. If the lacquer is not fully cured you can buff out the repair and it will look great, but it will shrink back as it continues to cure.

If time is a factor in the repair I go with the CA, but it can tricky. It is easy to make a mess of a finish if you haven't tried this repair before. Be sure to take you time and you should get good results.

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Butyl Cellosolve or Cellosolve Acetate is the stuff to use if you are going to try to melt old lacquer. I do a little spray with an airbrush, then drop fill the ding, then airbrush a few light coats of lacquer over it and finally, another shot of Cellosolve. I give it back to the customer and tell them to come back in 2 months.
I've tried the CYA that is supposed to be "finish" repair and I don't like it. It's too hard and the lacquer around it keeps shrinking. It doesn't.

You know too the Glue Boost products that Rick Rosenberg introduced on the OLF a year or so ago are excellent solutions for finish repairs. I believe that he was a sponsor at one time and if you go to his web site there are a bunch of testicalmonials... from some very notable Luthiers proclaiming love and devotion for these products.

We tried them too and are most impressed. From CA accelerator that will not leave you with the white foam blues to some polishes that seem to work better than our ole trusty McGuires we think that Rick is on to something good and we all benefit.

Anyway add our name to the Glue Boost fans, we like it.

To avoid the witness lines in nitro, or any finish for that matter when making repairs, as always it comes down to prep work. Cellosolve or any retarder actually can be used to soften up and blend nitro. But I only use that on large repairs myself and even then mainly on older finishes. For other small repairs I prep the surface by first cleaning really well to remove any polish that may be left which in itself may not be enough to cause adhesion problems but can and will cause witness lines or halos. Next I texture the surface around the area with either 600 wet/dry or some maroon scotchbrite. This opens the surface to allow the new finish to bond and provides a base texture under the repair at the edges to help blend the two when polishing out.

I too dislike CA for drop fills as it is always harder than the original finish. But on poly finishes it is one of the only choices.

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Brian

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

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Never heard of Cellosolve. Similar to acetone? This ding was the size of a match head. Would you use it on something like that?

I like the "come back in 2 months" part. Never would have thought of that. No reason they can't keep playing.

Good advise -- plan and allow time for the nitro drop fill shrink back. I am old school on this process.

Have not used CA for finish repairs -- but seems to me there is no way to predict if there will be variance in appearance as the dis-similar coatings age.

_________________
Ken Cierp

http://www.kennethmichaelguitars.com/

I don't know Hesh, I think you droped the ball on that one.

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Pat

Not at all Danny. I've heard it called epoxy thinner also. Much more powerful than acetone...dangerous to your health too. But then, what isn't these days...

No need to get testy, Pat.

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

Butyl Cellosolve is also called "retarder" and "blush remover" and "flow out". It is a slower evaporating solvent that allows the lacquer to set up more slowly (allowing trapped water to dissipate and the film to flatten out more. Like most solvents it will dissolve the old lacquer and help it blend into the new. Mohawk sells it in spray cans and calls it "No Blush Blender" (If sprayed too heavily it can sometimes cause orange peel!)
For drop fills I like to use thickened lacquer - lacquer that has been left open and lost some of the thinner components.

Yep, carefully get some retarder in there then drop fill with thick lacquer. You'll always see it, but this method gets you a little closer.

Please don't use super glue on a lacquer finish.

Yeah I must have been nuts... to bring that up....

CA drop fills are VERY common and these days there are even special CA formulations specifically for finish repairs including nitro. Welcome to the 20th century, er... or is it the 21st century now...

One advantage is that drop filling with nitro you and George Costanza have to worry about shrinkage, not so with CA. Nitro drop fillers have to wait for curing, the wait with CA is 20 minutes maybe on a long day.

As for appearance I would suggest folks try/learn on a sacrifice panel - it's easy, fast and in my experience invisible.

Regarding longevity Rick Turner has been keen to remind us lately that we are coming up on the 100 year mark for the invention of nitro and it's predicted that nitro finishes everywhere are going to start deteriorating at an advanced pace. Could be that over time the CA drop fill might be the only finish left on the instrument if you wait long enough..... And we all know that famous quote about in the long run.....

Thanks for the info. I most always use thickened nitro but next time I'm by the Mohawk store I'll pick up some retarder. I'm thinking it would be handy to have around for straying during periods of higher humidity.

Retarder is crucial. Just as necessary to have as thinner. Be careful with it, though, a little goes a long way if you intend to add it to lacquer to spray. As a "pre-drop-fill" I'll razor blade the fat side of a flat toothpick and thin it out towards the tip. Soak the chisel tip of the toothpick in a little cup of retarder and use it to apply a little bit at a time directly into the intended spot. Rinse/repeat 3 or 4 times. The key is being clean and patient. Retarder will f-up a lacquer finish if it gets anywhere other than its intended target causing way more work than is necessary. Use with caution, and for pete's sake keep the cup of retarder as far away from the guitar as is feasible.

I have tried fixing lacquer dings with CA but I encountered a serious problem: Somehow the CA would react with the finish, or something and basically now it creates something that would always sink just a little lower than lacquer when sanded flat and polished. Meaning it leaves a permanent mark that will not come out no matter how many coats of lacquer you put over it, requiring a partial refinish. This happened to a Kamaka Ukelele and a few other instruments.

I do not think CA is a good solution for lacquer fixes, perhaps the gluboost stuff will fare better. But I recommend lacquer drop fill if you want an invisible repair.

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

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http://www.gearupproducts.com/videos.html Nitro drop filling works great when you know how to do it and build it up proud of the surface before attempting to level and buff. Here's a link to Gear Up products which have been nothing short of embraced... by many notable Luthiers who work in the trade, do this stuff every day... and as such have direct personal experience with using CA for drop filling... successfully. The primary two advantages are very little shrink back which is a big issue with lacquer and the repair can be completed in hours not days....

Although CA is commonly used for drop filling poly finishes it does work well with lacquer too and some of these videos will detail how folks are using CA successfully.

As always and since CA is a term generically used there are differences in formulations from brand to brand and the Gear up stuff was specifically formulated for the kinds of things that we do. I doubt that all CA's would work as well. Gear Up's accelerator does not create the dreaded white foamy mess that other accelerators do produce.

We had good luck with other CA's, quality CA's too but never, never used accelerator and instead simply waited 20 minutes or so before adding any additional for the build and we waited longer before scraping back.