Shellac as finish?

[rogthefrog]

Is shellac a usable substance for a guitar finish?

[Frank Ford]

Originally Posted by rogthefrog

Is shellac a usable substance for a guitar finish?

Yes - Martin managed pretty well with shellac as a guitar finish for the first hundred years or so.

[rogthefrog]

Originally Posted by Frank Ford

Yes - Martin managed pretty well with shellac as a guitar finish for the first hundred years or so.

Good to know. Is it applied with French polish technique? Or sprayed?

I know nothing whatever about finishes

Thanks for the information!

[B. Howard]

it was applied as a french polish on Martins prior to the mid 20's, sometimes over a varnish base on lower end models. Spraying didn't start to be used for application until they started using lacquers.

You can however spray shellac though it will not be very durable when applied this way typically.

[Hot Vibrato]

Originally Posted by B. Howard

You can however spray shellac though it will not be very durable when applied this way typically.

This post implies that shellac is less durable when sprayed on as opposed to the french polishing method. Am I interpreting that correctly?

[redir]

Shellac is my all time favorite finish. I was always told that a shellac finish, French Polish, will be weak, require a ridiculous amount of care, is not a good barrier and so on so I avoided it. Instead I used lacquer which can kill you, water based finishes which are blue and don't buff well, poly wipes, Varnish, and a whole host of other methods till one day I decided to try this French Polish thing and.... It's great. And if you don't use your guitar as a canoe paddle then it's a perfectly suitable finish. And yes an errant pick will scratch the top like it will not do with a poly finish but then, think about that for a minute...

[tahoeguitar]

It was the traditional finish used on guitars and other stringed instruments before nitro lacquer. The usual application technique was French polish since nobody had invented the spray gun yet. It is made from bug excretions and most consider it more natural environmentally friendly than Nitro. It still off-gases a certain amount of alcohol during the application process, probably not as much as Nitro offgases toluene and acetone, methyl ethyl ketone, and other nasty stuff. Modern lacquers are being formulated with less toxic solvents but I still don't want to breathe either industrial alcohol or lacquer fumes. Fumes from a good syrah or India pale ale are another matter.

A shellac finish is easily damaged by water and alcohol... OTOH it is easy to repair. Nitro is pretty impervious to water, alcohol can dull it or do more serious damage if left for awhile, and it also repairs easily. There are water based lacquers out there that don't offgas much and are reputed to be less toxic. The earlier generation water based lacquers were not as clear as nitro but I think that's getting better. The catalyzed urethanes being used by the big factories are impervious to everything except bullets. Fumes from some of these catalyzed finishes are super super toxic. They generally don't repair well.

Then there are the varnishes which I know nothing about other than some people are using and liking them for guitar finishing.

[dekutree64]

Originally Posted by tahoeguitar

A shellac finish is easily damaged by water and alcohol...

Is that with natural or dewaxed shellac? IME, dewaxed is completely waterproof if the film is unbroken. Can't wet sand FP because it's so thin you quickly make holes in it and then the water soaks into the wood. But I've tried leaving a pool of water to evaporate on a shellacked surface and no harm done. Steam will damage it of course, but that's first from the heat, then from the water.

I haven't tried waxy shellac, but from what I've heard, it has higher abrasion resistance but lower water resistance.

[Frank Ford]

Shellac is not commonly sprayed or brushed for very good reasons.

Compared to nitrocellulose or acrylic lacquer and other solvent lacquers it is absolute murder to clean out of fine spray gun orifices if it has been let dry too long.

Shellac has an unbelievably high surface tension, which makes for a "fat edge" around any little holes as it literally crawls right up out of pores or whatever an deposits itself on the surface above. Spraying shellac is asking for moisture problems because alcohol is hygroscopic as all get-out, so blushing is easy to obtain.

Brushing shellac gives new appreciation for the phrase "flow-out" as you wish it acted like varnish, which is self-leveling.

Wiping shellac actually pushes the material down into pores, scratches and other divots, allowing the material to be spread thinly without lumps. The process of French polishing is a method of allowing repeated coats to be applied in incredibly thin layers during a single session as the rubbing pad is lubricated with an oil that's also incorporated into the finish.

Such oils also become part of the final film and contribute to its durability, flexibility, hardness, etc.

That's where practice comes in. Like guitar playing, French polishing is all about practice. It is absolutely possible and reasonably convenient to build as thick a shellac finish as it is a lacquer one. It's absolutely possible and reasonable to obtain the same level, brilliantly reflective high gloss that's typical of a fine lacquer finish.

I'd say that when I'm building a finish that way, I may pass the shellac-charged pad over any given area of the finish about once a second, with the shellac being deposited and alcohol flashing off at each stroke:



As the film builds, it becomes more delicate, so it's necessary to sense and adjust technique continuously. Takes practice to get the "feel" of it, and if you think that doesn't apply to you, well, you're thinking wrong.

Practice. . .

[Alan Carruth]

Some years ago Martin Schleske tested the properties of a number of finishes and published the results. Since he's a violin maker he concentrated on ones that get used on fiddles, but he did test both shellac and nitro. Nitro was the hardest finish he tested; shellac was about 2/3 as hard, and most of the rest were softer.

Gibson used to use varnish, while some of their competitors used shellac. I've seen an old ad for Gibson that talked about how their competitors killed the tone with their 'glass hard' finish. These days nitro is considered 'soft'.

One of the advantages of French polish is that it can build up a nice looking film that is very thin, thus adding very little weight or stiffness. A very thin layer of anything is not much protection, no matter how hard it is.

The problem is that most 'affordable' guitars these days are finished with something like UV cure polyester, which is relatively bullet proof. Since it's so hard and goes on so thick by comparison it probably does hurt the sound. Somehow, though, it's almost impossible to communicate the notion to somebody trading up for better tone that they have to pay attention to the finish. The guitar is more expensive, and thus should be better in every way, right? So how come the finish won't withstand what they've come to think of as 'normal' playing? I've had guitars pretty much trashed at shows, despite a lot of effort in carefully trying to explain that the finish is not hard, and they will need to be careful.

Shellac is also soluble in alkaline water solutions, and for some folks that means 'sweat'. I've seen people who have worn through the French polish on the back of the neck in a couple of weeks. Back when you bought your guitar from a local maker you'd just take it back every once in a while to renew the FP, but that's not common these days.

The bottom line is that FP is a great finish IF you can get the customer to treat it the way it should be treated. These days I tend to only use it on the tops of Classical guitars, and then only if they're spruce. I've had too many bad experiences with FP over cedar.

[redir]

I have brushed on shellac though. In fact I start all my FP projects in this manor. I brush on about 3 coats then sand back nice and flat before I then FP. It's a good way to speed up the process. But I have also just brushed it on, wet sanded it out and polished it too. You have to make the shellac very dilute with alcohol. It's not something I actually measure. I just pour in the alcohol till it's right. You basically have to take one full brush stroke and just leave it. Don't even be tempted to touch it again.

[Howard Klepper]

I have sprayed shellac finishes on guitars with no ill effects or problems.

Whether the end product is in some way inferior to a French polished shellac is a subject of longtime debate. Surprisingly enough, those who French polish are usually convince that the process increases the density and strength of the finish; those who spray think not. I personally cannot see how the amount of pressure applied in French polishing can have any effect on the resulting finish. It takes enormous pressure to compress a liquid or solid.

[TNO]

Fresh-mixed shellac from garnet flakes sprayed through a preval makes for a quick and easy finish for a Fender neck. Gives a great vintage look except it won't check. Ive never managed to wear through it even on a maple fingerboard.

[printer2]

Originally Posted by Frank Ford

...Brushing shellac gives new appreciation for the phrase "flow-out" as you wish it acted like varnish, which is self-leveling....

Originally Posted by redir

.... You basically have to take one full brush stroke and just leave it. Don't even be tempted to touch it again.

No kidding. I know, probably not the same as made up with flakes but I bought a can of shellac and only found out it had wax so I thought I would use it on a frivolous electric guitar build. Found out it it did not wet out all that well and did not like being disturbed after it is laid down. Sanded through it a few times, eventually sanded it all off and used poly.

[Frank Ford]

Originally Posted by Howard Klepper

. . .I personally cannot see how the amount of pressure applied in French polishing can have any effect on the resulting finish. . . .

Same here - once the alcohol evaporates, the solid shellac left behind is probably the same.

BUT, when French polishing with oil lubricant, some of the oil combines with the shellac as an interstitial mixture, even though they have different solvents. Some practitioners believe the oil is the most important part of the finish, although that seems a bit extreme to me. There's no doubt that the appropriate oil polymerizes over time and adds to the finish in its hardened state. That's clearly a phenomenon unique to the method of application.

Whether it improves the finish, how much it improves it, or whether it contributes to softening, well, that's a far more complex discussion, you betcha!