Couple of Shellac Questions

[nikpearson]

Originally Posted by redir

Wouldn't the rubbing of cloths, sleeves, leg rests, and so on polish out the guitar if it was simply satin-ized with steel wool though?

But it can be re-satinised (is that really a word?) easily enough. Glossy finishes tend to dull, whereas matt/satin finishes tend to shine up. A little care when handle the instrument dramatically reduces the risk of this happening. I started wearing a running sleeve when playing in short sleeves for this very reason. No more polishing the lower bout where your arm rests, and no more pleasant for your arm as well.

[Quickstep192]

I’ve used Renaissance Wax on my shellac finishes with great success. It knocks down the gloss ever so slightly and I think it looks fantastic.

Often handled surfaces will be polished with use. The neck on my 30 year old Taylor was finished with a flat finish (finish with additives, not deglossed with steel wool) and it’s now shiny as can be. I just embrace the shine.

[conecaster]

Originally Posted by Alan Carruth

A good French polish job is .002" thick, or a bit less. Most brushed varnishes are a bit thicker, although some will end up at .003"-.005" or so. Typically a spray finish will be .005" or thicker, and in some cases much thicker. I have a cut off piece of an Ovation top that has .04" of hard water-cure epoxy for a finish, sprayed on in one coat, or so I'm told.

The best test of finishes I'm aware of, Schlekie's paper in the old Catgut Acoustical Society 'Journal' pegged shellac as about 1/3 less hard than nitrocellulose lacquer. Compared with many oil-resin varnishes that's pretty hard, although some of the modern ones seem to approach nitro in hardness. Shellac is also tougher than nitro; more likely to dent than chip at a given thickness. At .002" thick no finish is doing much as an 'armor'. You can, of course, lay on shellac as thick as you like.

One technique that helps speed the process is applying hot hide on tops while wiping it off in one stroke. For sealing under any finish this works well.

Personally I have no use for straight shellac. When I did restoration work for Gruhn years ago we used a formula sold by Metropolitan music.

I think of FP as a technique more than anything. It can be done using any alcohol soluble material. Elemi, Mastic, Pontaniac, Dammer, Sandarac, Copal as well as Shellac. The problem with Shellac is moisture resistance. By adding other resins the FP film can be more durable.

The use of Lacquer in FP has become much more standard in Spanish guitar making. My old friend and renowned classical and Flamenco maker, Robert Ruck, shared his use of lacquer in shellac. The result provides a durable and in some ways better result in that the oils used in the padding on technique tend to absorb into the film like is the case with other plasticizers in lacquer. Personally this technique is my preferred approach. I recently restored a top that was covered in dings using this after filling everything with shellac mostly.I had never used the Stewmac flakes and was impressed with that material.

When you blend in Lacquer, up to 30% (hard to estimate given degrees of cut), an amount of acetone and or Lacquer thinner is added to the alcohol. The solution is not that stable over time and the lacquer resins fall out. But the Stewmac stuff was better at suspending the lacquer.

My opinion is, that for all the mystique surrounding this technique I prefer modern finishes, except Polyester. I measure the film I remove for the bridge on every guitar. I usually have about .003 on a top.

If there is one thing I did early on that I do not regret, it was getting away from Nitro. I see guitars I made decades ago and they still look really good. The toxicity of the stuff is also a deterrent. It is sprayed against walls of moving water to capture the toxic over spray. Its sprayed hot to thin it out of a gun at higher solids content, reducing the percentage of Ethyl Butyl Ketone.

Nitro is a moving target, its 2/3rds plasticizers that slowly leach out. When restoring decades old lacquer it becomes very thin cellulose. So FP to restore it is a valuable approach.

The lacquer combo with shellac keeps the film looking good and durable without gumming up in heat or turning milky from moisture.

I have finished interior back and sides for a long time. I like spraying Deft semi gloss from an aerosol can. No over spray, it looks good enough.

Paul McGill

mcgillguitars.com

goacousticaudio.com

[redir]

Originally Posted by conecaster

One technique that helps speed the process is applying hot hide on tops while wiping it off in one stroke. For sealing under any finish this works well.

Can you elaborate on that?

[conecaster]

Originally Posted by redir

Can you elaborate on that?

Hide glue is of course heated in water to melt into liquid.

You don't brush it on and let it sit. As soon as it cools it is setting up.

So you want to brush it on followed by a paper towel to get it off while its still warm enough to be liquid.

The heat and moisture opens the fibers and the glue seals up the surface.

Then after it cures sand over it lightly with 320 before finishing.

Another old world trick. Violin makers used egg whites. Another protein saturation.

[redir]

Interesting I never heard of that trick. I have used egg whites and it works quite well.

[Alan Carruth]

conecaster wrote:
"Nitro is a moving target, its 2/3rds plasticizers that slowly leach out."

That's an issue for sure, although modern plasiticizers are much more stable than the old castor oil. The real issue with nitro is that it's the little brother to a high explosive. Instead of being nitrated to 90% or more it's 'only' taken to about 18%, which is enough to make the cellulose soluble in a bunch of solvents you really should stay away from. Those nitrated monomer units in the long chain can be 'kicked over' by something like UV light, and convert to CO2, NOx, and so on, releasing energy in the process. The low nitration fraction keeps this from becoming an instant chain reaction, the way absorbing nitroglycerine in sawdust or cat litter makes it into (more or less) stable dynamite. Nitro sure does burn fast, though. Eventually those nitrated molecules do break down, one by one, and if you take one brick out of every six from the wall you have...

Museum conservators these days consider nitrocellulose to be 'toxic', in the sense that the nitrates released as it breaks down attack other things. Ever notice the corrosion on tuners that have been in a closed case for a long time..?

Freash shellac is soluble in alkaline water solutions and alcohol. However, it tends to cross link slowly over time and become less soluble. After 75 years or so it's darn near bullet proof. A nitro finish that age is toast, unless you feel that the purpose of finish is to discolor, check, and flake off, artistically....

No fan of nitro...

[redir]

I'm a fan of Nitro because it's a hell of a lot easier to spray on and wait 4 weeks to polish out then to make 28,000 figure eights with a French Polish mouse pad.

[Fathand]

Originally Posted by redir

I'm a fan of Nitro because it's a hell of a lot easier to spray on and wait 4 weeks to polish out then to make 28,000 figure eights with a French Polish mouse pad.

Have you tried EM6000? Sprays and burns in like Nitro can buff after 1 week or less. Water based, less toxic.

[Belbein]

This is just my personal prejudice, and I build for fun, not commerce, so take it for what it's worth:

I now use exclusively French Polish. That's because I love building but HATE HATE HATE finishing wood. By the time I get to finish I'm so anxious to be done that I don't want to take the time to do it well and I invariably do a bad job. With French Polish, the method requires that I work on it for a few minutes and then WALK AWAY. The walk-away requirement of the method itself builds in rest-and-reconsideration time. It forces me to be patient and let it develop. The results are fabulous, too. When I walk in the next morning to begin again, the beauty of the incremental layers of finish are always inspiring.

In addition to that, I have various materials allergies and asthma, and a spray or highly chemical finish is deadly for me. French polish is just plain healthy.

And you can always take a sip of the everclear. ...

[redir]

Originally Posted by Fathand

Have you tried EM6000? Sprays and burns in like Nitro can buff after 1 week or less. Water based, less toxic.

I have not but have considered it. I still have a bad taste in my mouth experimenting with water base finishes some 20 years ago now.

[redir]

Originally Posted by Belbein

This is just my personal prejudice, and I build for fun, not commerce, so take it for what it's worth:

I now use exclusively French Polish. That's because I love building but HATE HATE HATE finishing wood. By the time I get to finish I'm so anxious to be done that I don't want to take the time to do it well and I invariably do a bad job. With French Polish, the method requires that I work on it for a few minutes and then WALK AWAY. The walk-away requirement of the method itself builds in rest-and-reconsideration time. It forces me to be patient and let it develop. The results are fabulous, too. When I walk in the next morning to begin again, the beauty of the incremental layers of finish are always inspiring.

In addition to that, I have various materials allergies and asthma, and a spray or highly chemical finish is deadly for me. French polish is just plain healthy.

And you can always take a sip of the everclear. ...

Yeah that's why I started using shellac too, health reasons. I only spray Nitro outside so that limits me to summer and fall, fall being the best season, because I will only do it outside.

[LHawes]

As a follow up to the OP, I am spraying rattle can nitro and have a protective coat of shellac on the top. My question is, do those who use nitro leave that coat of shellac on, then spray nitro? Or do you (would you) sand off the shellac before spraying? Or leave it on, then spray? I know leaving shellac on then spraying, or sanding it off then spraying are two good choices but am curious about others' choices and perhaps why. It also seems that the shellac adds a bit of color that nitro may not? Never sprayed nitro over bare spruce so don't know about any color change.

Thanks

[LHawes]

Originally Posted by Fathand

Have you tried EM6000? Sprays and burns in like Nitro can buff after 1 week or less. Water based, less toxic.

I've used CrystaLac's Brite Tone on a few guitars with great results. Thought I would try EM6000 as LMI had it on sale but didn't really like it. It seems to polish up OK but during finish sanding the wetRdry sand paper would load up with those little pieces of finish, after at least 2 weeks of cure time, and turned me off from EM6000. Won't use it again. The CrystaLac though was great as I stated and will use it again if my current nitro experiment fades.

[lar]

The owner of a Shellac company gave a talk at my local woodworking shop recently. It was interesting. You may like his videos - one of which is finishing a guitar with Shellac. He sells the Shellac flakes in different colors, and the denatured alcohol.

One of his products is his own blend of Shellac and synthetic resins - which he calls SF-Royal-Lac Post Catalyzed. It's supposed to be harder. Here is the link to it:

https://woodchuckers.com/products/sf...yysed-catalyst

And the link to his home page: https://www.shellacfinishes.com/

The website is a bit glitchy - be patient.