Acoustic Guitar Construction

Anyone spraying shellac -- as if it were lacquer?


Actually -- it seems perfectly logical to me -- spray, level, polish. Why not?

I've only done it with touch up in a air brush setup. But I think it would work just fine.

Strangely enough, I'm getting ready to try that, if all goes well. I'll be using a preval sprayer on some scrap first naturally. If it comes to fruition I will report!

There is a product called Royal Lac I think it is a shellac? -- I see some guitar finishing talk but know nothing about it?

Royal-Lac is shellac with resin additives that cause crosslinking. The additives are said to improve shellac's susceptibility to alcohol, water, and heat damage. I have been conducting a test of it that is now into its 6th month. So far, so good. The company that sells it is knowledgeable, responsive to luthiers, and dedicated to integrity. (https://www.shellacfinishes.com/)

Robert O'Brien endorses it on the sales site after finishing a series of sample boards using brush, pad, spray gun, and French polish to apply it. He said, "All results are nice. The product is indeed alcohol and heat resistant which is nice. Congrats on a nice product."

Tim McKnight has used it for spraying guitars and praises it as resulting in "the highest gloss that I have ever seen in any finish". He goes on to say "The clarity is like none other".

This is McKnight's result.

It has actually been 7 months (after I looked at my notes) since I applied Royal Lac to my "guinea pig" deconstructed Korean made Harmony. Like I said above, it looked good, considering how I finished it. The guinea pig has some kind of catalyzed polyester finish as a filler base that I was unable to remove. I padded on 6 coats of Royal Lac with a wad of cheese cloth, nothing fancy. This produced a shiny - as opposed to satin - finish. I did not attempt to level or rub it out.

First I applied a pool of 91% isopropyl and let it stand until it evaporated. It dulled the finish inside the perimeter and left a ridge around the edge that I could feel with my finger.

Next I applied a pool of denatured ethanol and let it stand until it too evaporated. Same result as the isopropyl.

Finally I applied a pool of Behlen's 631 lacquer thinner, left on until it evaporated as well. It did such minimal damage that I could hardly detect it, just a couple of spots about the size of a pin head or smaller.

I will let the two alcohol damaged areas dry overnight. I anticipate they can be easily buffed out after carefully sanding the ridges flush. (The ridges are tiny.) The lacquer thinner damage, small as it is, should simply buff out. These flaws look much easier to fix than what happens after I drop fill with thick lacquer or CA.

Royal Lac seems like it is pretty tough stuff.