Spraying versus french polishing

[Jim Bancroft]

Question- I know these are just methods for applying finish, but is the outcome different.
If shellac is sprayed on and buffed out is it going to look different, in any way, versus, if it was applied with a pad, in the french polish method.
I can't see where there would be any difference once the finish was completed, but I'm not an expert on this stuff.

Jim

[Bob Webster]

Actually, Eugene no longer uses walnut oil. It's not at all tougher to do but, like linseed oil, walnut oil will incorporate into the finish by oxidative crosslinking. That means that the finish is much more resistant to alcohol and so, it's a whole lot harder to refinish or touch up with more shellac/FP. Non-polymerizing oils like olive oil or mineral oil are the choices now of folks who use oil as a lubricant. Or..., you can do the job without any oil, like Cyndy Burton does. How she does it is beyond me. She uses a blonde shellac that she bought 50lb of a long time ago and I suspect it has a bit of wax still in it. She's offered to have me try some of it but I haven't had a chance to get down to Portland to get some.


Cheers,
Bob

[Matt Hayden]

I think the crosslinking is why I like it - it's a tougher finish. Yes, it's harder to repair, but honestly, what guitar doesn't get some dings? I'd rather have a tougher finish that's harder to touch up than one which wears a lot....just my opinion.

[Bob Webster]

I agree wholeheartedly with the need for more toughness. It's really heartbreaking to see someone put a nail dent in your newly FPd guitar top. I'm just starting to FP an Antonio Marin copy I'm building and I've included 10% sandarac in the shellac, following a lead from Frank's site. I'm hoping for a little more toughness and, potentially, a little higher gloss on buffing out.

[Ned Knepp]

Bob, did the sandarac tint your shellac?

[Bob Webster]

Not that I can tell, Ned. I use Behlen superblonde shellac and the applied finish doesn't look any different than before. However, dissolving the combination of powders (resulting from aggressive grinding in my dedicated Braun coffee grinder) is different. Without the sandarac, the shellac is a clear solution in about an hour or so. With the sandarac and filtration through a coffee filter after one hour, there's still a haze to the solution that doesn't go away for another couple of days. Application, however, seems not to be any different. I bought my sandarac from a bookbinder's supply in New York.

Cheers,
Bob

[Ned Knepp]

Thanks for the info, Bob. I haven't tried sandarac in my shellac but I wouldn't mind giving up some simplicity in repair for a harder, more resistant finish. I like to use a pretty dilute cut of shellac, maybe 1/4 lbs or less. I like the way it works but it takes time to build. Since I don't do this professionally, the time to build a finish isn't usually an issue but I would like a "harder" finish because it's so thin.

Do you think the "haze" you had in your solution after straining the mixture was undissolved sandarac? I'm wondering if you actually ended up with the sandarac to shellac ratio you though you were getting. In retrospect, do you think it might have been better to wait a couple of days before filtering the solution or perhaps dissolving the sandarac separately then combining it with shellac?

Thanks,
Ned

[Bob Webster]

Sandarac is a resin collected from a small African conifer and does not have a discrete chemical formula, which is to say that there is alot of different crap in there, Some of that stuff isn't necessarily so soluble in alcohol. Additionally, there could be insect parts, bird stuff, etc.

The haze I saw was only marginally reduced by the initial filtration and there were no significant sized particles prior to filtration, so I'm reasonably sure that I didn't lose much sandarac at that step. I used 5.7g of it along with 2oz of shellac into 8oz denatured alcohol to make up my doctored 2lb cut.

Dissolving the sandarac beforehand is a really good idea. One could then just measure it out and introduce it to the shellac using a syringe. Mixing the two solids before grinding, on the other hand, provides some bulk in the coffee grinder to pulverize it and speed dissolution.

Cheers,
Bob

[Jim Bancroft]

Frank,
Guess I was extremely lucky when I sprayed it. The guitar was a 1926 Martin, with I'm guessing an original shellac finish, it wasn't lacquer. My purpose was to add finish over the original finish.

I tried french polishing it, but was having problems. So I turned to spraying it on. I mixed a 1 lb. cut, so it was fairly thin. Sprayed numerous light coats, light sanding(800 grit?) between some of the coats. Probably applied 5 or 6 coats before I figured I had enough to cure and buff out.
The finish turned out fantastic, I couldn't have expected better even if it was french polished, a deep rich high gloss, thin hard finish, that rubbed out perfectly.
I didn't have any of the problems you or others have mentioned, orange peel, run, gather, ect. The stuff sprayed perfectly. With the results I had, I wouldn't shy away from doing it again.

Still, no one actually answered my question," would shellac sprayed look different than shellac applied with the french polish method"? My quess is it wouldn't, if they are both high quality work.

Thanks
Jim