Official Luthiers Forum!

So I have Been building acoustic guitars for a while and also some gibson style electrics and I have done french polish
some other natural finishes and used Nitro. I started a hand full of telecasters and I had and issue with the Nitro lacquer cracking if even a speck of water gets in a drilled hole or cavity. I have never had this issue before. I sanded back the finish and started again and wet sanded this time staying clear of the holes. Made it thru mosty but ended up with a crack that will be hidden by the pickguard. I then went to put the ferrels in I have the kind that go in flush and just a little pressure chipped and cracked the lacquer.

Question 1 Is there a way to get thru this with out wet sanded? What are some alternative methods?

Question 2 Ferrels in before finishing? If after how do you clear the lacquer back enough to push them in?

What kind of lacquer are you using. It sounds like it is too brittle with insufficient plasticizers.

You can dry sand with special sandpapers. Or you can wet sand with mineral spirits. I prefer the dry sanding.

For the inserts, you want to heat them with a low wattage soldering iron to press them in. Basically you set them on the hole and use the iron to apply pressure. As they heat up, they soften the lacquer. Be careful not to overheat, though.

Barry,

I am using Mohawk Stringed Instrument Lacquer. This particular guitar was painted blue using the stewmac pigment. Would this be the result from adding to much pigment?

What type of special paper do you use for dry sanding?

Roger,

Thats sounds like the way to go! I have a Weller digital soldering iron that I can adjust the temp on. Any guess at what the best temp might be?

Pigments can definitely make finishes brittle.... Sometimes it's a concentration issue ( to high a percentage of pigment) others its a PH imbalance caused in the coating by the pigment. Modern coatings have become very PH sensitive.

But it could be other things. Most modern lacquers are too soft as they are and are over plasticized so....Too much film build will cause finish to be brittle. Contamination between coats can make a finish appear brittle but it is actually adhesion problems between coats. Improper prep can do the same.

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Brian

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

https://www.howardguitarsdelaware.com/

the tuner holes are the worst offendors - i paint lacquer carefully in the holes with a brush from both sides during finishing to ensure all is waterproof before water gets any where near raw wood. Always a good idea to carefully open the holes to width with a backward running drill bit or step drill if you can get the right size - 8.8mm is ideal for kluson style tuners.

Press tuner bushings in hot, I use my soldering iron to heat and push them in. No chips!

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Brian

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

https://www.howardguitarsdelaware.com/

I chamfer the lacquer around any holes before installing hardware.

I've been using Behlen Instrument Lacquer with good results. I wet sand to 12000 with Micro Mesh so there's a lot of wet sanding involved and haven't had any problems with cracking.

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Julie Moriarty
http://JulimorCreations.com

Wes

I build Teles also, but this principle applies to any guitar. I spray nitro on all of my guitars. Old Picker is exactly right. The water from wet sanding swells the wood end grain in any open hole, especially if you are using something like figured maples or ash. These woods are very porous. They suck up water and swell. The lacquer is stretched. After the water dries out of the wood, the wood shrinks and the finish pulls away, leaving a nasty blister. This happens around the tuners, ferrule holes, bridge screw holes, control holes, etc. This will happen with any nitro. I apply CA glue with a pipette to seal off the end grain in the holes before I apply finish. CA attacks lacquer so you want to seal first and then finish. Don't use an accelerator. It can leave a white residue. As a word of caution, CA shows under finish with some light woods, so be neat and practice on scrap. I hope this helps.

Thanks for all of the help everyone.

I settled on using automotive sanding film discs recommended by the guy at the local auto paint store. They work great dry and I can use them by hand or on the air sander. I have been having good results sanding dry then onto three grits on the buffing wheels.