Official Luthiers Forum!

hi. on my 4th time doing french polish i got something similar to shattered glass on the top. definitely a bummer. i'm guessing that i went too quick between coats and maybe too heavy? i'm thinking the fix is to sand down the finish and start over. any advice on how not to do this again and how to fix would be greatly appreciated!

_________________
http://www.wideskyguitars.com
https://www.instagram.com/wide_sky_guitars/

Using regular dry mixed shellac? How heavy a mix, 4 lb cut? Lighter? Pre-mixed?

_________________
Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

i use dry mix. starting with 2lb then move to 1lb.

_________________
http://www.wideskyguitars.com
https://www.instagram.com/wide_sky_guitars/

Yep, probably went too fast for that much shellac. But to me, the beauty of FP is that you can refine a surface to perfect smoothness without needing a thick layer of finish on top. Focus on filling the micro-structure of the wood, and only leaving a soap bubble thin layer on top of the highest points of the wood itself. If it takes a lot of coats to fill the micro-structure, then sand or scrape level to remove the excess shellac, and do one more pass to fill the roughness left by that.

Ideally you should be able to use technique to drag shellac around and level the surface before ever building to an excessive amount of shellac, but my attempts often end up just making a mess of streaky gummy shellac... though making a mess and then sanding/scraping level is fair game, and can still be faster than doing a ton of polishing passes to fill a rough area.

yup, thats likely the cause. I did the same thing, trying to finish a guitar quickly as I was moving. they also do that around where the forearm hangs over the top, from the humidity in your skin. dont know about the repair, i didnt bother. probably trying to go over it hoping it will amalgamate back to a smooth finish would be in vain if you are going for flawless. i switched to nitro, but my old fp guitars still have a noticeable tone edge, too bad its such a job to get it perfect and keep it nice looking.

I'd use alcohol to remove the finish, followed by a light sanding. A little
bit of mess, but less chance of thinning the wood more than you want.

_________________
Gene

Politicians and diapers must be changed often, and for the same reason- Mark Twain

Sergei de Jonge taught me a nice trick to remove the shellac ... cut a couple of layers of paper towel to the approximate shape of your top, lay them on the top and gently squirt alcohol on them to soak them ... leave for 3 minutes and then use them to wipe off the shellac. Lightly sand and start your French Polishing again. You'll be surprised at how quickly it builds after this process too.

Thanks for the advice! David, I am definitely going to try this. I'll let you know how it goes.

_________________
http://www.wideskyguitars.com
https://www.instagram.com/wide_sky_guitars/