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I just finished an instrument using French polish. I had a classics builder I know walk me through the process. And, wow, is it ever labor intensive. THAT SAID; I really don’t mind the time and work part. The process WAS very enjoyable ... really

I’ve used EM6000 on about 7 instruments and really like the end result, but the depth the French polish brought out was simply amazing and I don’t get that with lacquer.

My question is: can I maintain that visual depth if I do a French polish UNDER the lacquer? Am
I shooting myself in the foot somehow? Maybe going in circles?
This is an incomplete thought for me, so I’m asking for input to help me connect the dots.
Thanks so much
B


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Since French Polish is really a process for applying shellac that leaves a very beautiful and deep gloss, applying anything over it would, in my opinion, leave it as only shellac (which is quite nice in itself...). The final surface, thin application and depth are French Polish's forte's as far as I'm concerned. Might as well have sprayed or brushed a base of shellac instead of French Polishing if you lacquer over it. Plus, if there's any oil at all left on the surface, it's going to be a mess with lac sprayed over it.

Right now, I'm French Polishing a guitar using Royal Lac instead of plain old shellac, hoping to get some of that lacquer durability while still maintaining the looks of French Polish. I've French Polished most of my instruments for years now, with only an occasional nitro finish now and then. I love to polish, and it's nice to be able to do it without nasty fumes or the need for a spray booth, not to mention that it's a beautiful finish. I've got to say, I'm impressed with the Royal Lac so far. It's building very quickly, feels and behaves pretty much like the shellac I've always used and looks great. If this works out well in the end, I'll probably stick with it.

Here's a picture after a couple of polishing sessions with the Royal Lac:



Dave

Well EM6000 is not lacquer so...... and no water borne material will ever have the clarity and depth of french polish or lacquer. This due to the process used to suspend the resins in a water based medium.

Solvent based and 100% solids polys will give depth and clarity even beyond french polish.

_________________
Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

Although shellac sticks to most other finishes, and a wash coat of shellac can often be used as a barrier coat or sealer, not every finish will stick to a shellac finish. If you build up a shellac finish and top coat it with something else you may have adhesion problems.

Why do you want to use Lacquer over the FP? It's not at all uncommon to use shellac as a sealer followed by Nitro but as stated Em6000 is NOT nitro.

I understand that EM6000 isn’t nitro, however I was under the impression it was a water based lacquer. Pardon the ignorance


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I believe EM6000 is a lacquer, but it’s an acrylic lacquer as opposed to a nitrocellulose lacquer.

_________________
Andy
www.bounsallguitarworks.com

The reason water born finishes tend to be 'flat' or 'veiled' looking is that the first thing that wets the wood is not finish, it's water. The finish has not really wet the wood, and the light can't get into the structure of the wood. Many water born finishes are designed to be applied over a sealer such as shellac or epoxy that does penetrate. The finish in the water born material can bond to the sealer, and the two materials have similar refractive indexes, so there is not a noticeable reflection at the boundary. The manufacturer can tell you what seal coats would work with your finish.

One consideration is the old painter's rule of 'fat over lean'. Putting a hard surface layer over a softer one is a recipe for disaster. The soft finish can move with the wood, but the harder stuff doesn't go along and crazes. Thus oil painter use more and more oil in the medium as thay work to inure that the surface layers can move along with what's under them. Anything will stick to shellac, but nitro is a much harder material than shellac. If either the shellac or the nitro is too thick you can get crazing.

Again, check with the manufacturer on all of this.

"Lacquer" has been used as a lump-all term, just like "paint", "stain" and others. It has become so prevalent that it is hard to talk intelligently about finishes with other people. The manufacturer describes EM6000 as a water-based acrylic lacquer. I think it is important to add the water-based adjective to differentiate it from solvent based acrylic lacquer which has been around for decades.

I'm surprised to hear that nitro is harder then shellac because shellac shatters like glass. But of course a simple seal coat of shellac probably doesn't go against the fat over lean rule.

This is a bit of a detour to the original question, but I’m considering French polishing my next guitar. I would like to give it a sunburst. Would it be best to use stains directly on the wood or is it possible to tint the shellac and develop a sunburst with the French polish? I’ve only once done a French polish finish on a guitar but that was 25 years ago. At that time I used stains on the wood then worked the shellac over the top. I wasn’t entirely happy with the results as the stain couldn’t get the wood dark enough.

You might find some good information over on mandolin cafe - some of them do hand rubbed bursts under french polished finishes.

The original urushi lacquer, used in the orient, is actually a reactive finish made from the sap of a plant that is related to poison ivy. It's amazing stuff. I think that the use of 'lac' in the name of a finish is, in some sense, an invocation of that superior finish, just as they use 'mahogany' to refer to medium brown, medium density tropical woods to try to make you think you're getting the real thing. I'd bet 'shellac' was just such a usage.

Compared with nitro, shellac is pretty tough stuff; not as hard, but less likely to crack when flexed.

These days 'lacquer' tends to refer to a resin dissolved in solvent. You paint or spray it on, the solvent evaporates, and you're left with the resin. Normally, as with nitro or shellac, the resin on the surface is the same as the stuff dissolved in the can, and if you hit it with some solvent it will dissolve. MEK, the solvent for nitrocellulose, is less common than alcohol or alkaline water solutions that will dissolve shellac, and that's a good thing! Nasty stuff, MEK. They add other things to lacquer thinner to make it a bit less nasty, but not much.

Water born finishes are emulsions; droplets of finish suspended in water, analogous to mayonnaise or Titebond glue. The idea is to make the finish spreadable/sprayable without having to add in too much volatile organic thinner. As the water evaporates the little droplets of finish stick together to form the film. There's some tricky chemistry involved, but the finish itself can be almost anything. So a water born lacquer is lacquer that's been whipped up with some water and a minimum of solvent. And so forth.

Lacquer is just a word ... actually derived from shellac. It was the japanese process of finishing that involved mixing shellac with other ingredients to produce a shiny black finish. Here is some info on "Nitrocellulose Lacquers"
https://howardguitars.blogspot.com/2015/02/air-dry-lacquers.html

OK now a science/chemistry lesson.

The reason water based finishes lack clarity and depth has nothing to do with water or what hits the wood first. They have the same issues if applied over a cyano-urethane isolation sealer as they do over bare wood.

The reason is manufacturing and the process used to suspend a "water-proof" resin system in a water compatible medium. First you must understand there is no water in these "Water Based" systems! They are water based in the fact that they can be cleaned up with water before dried and in some cases successfully reduced with water. You can grind up dried NC lacquer and mix it with solvents and have a new batch of finish, you cannot do that with any WB product. Plastic resins (which NC lacquer is!) do not dissolve in water. They do not dissolve in things that are water compatible. Petroleum products and can only be dissolved in petroleum solvents....

So in order to make these coatings they first start by dissolving the resins in solvents like acetone in a very conventional manner. This is then mixed with a glycol based solvent. Glycols are unique in that they can mix with both mineral solvents and water, just not at the same time. Now comes the part that ruins the clarity..... we must remove the petroleum solvent. This is done through distillation which requires heat. A long slow heat so as to boil off the lighter petroleum and not any glycols. This heat causes the plastic resins to start to polymerize! Polymerization is the curing or "drying " process that causes these type finishes to form a hard coating as opposed to simple evaporation like NC lacquer. This partial curing links molecules and is the real reason ALL single component waterborne clears lack the depth and clarity of other systems that completely amalgamate or polymerize in one step on the finished surface.

The reasons some brands are worse than others depends on the exact chemicals & distillation process used. Until someone comes up with a way to get these resin systems suspended in aqueous medium without partial polymerization this problem will alweays be.

_________________
Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

As always, more complicated than it 'should' be. Thanks Brian.

Yeah thanks for that lesson Brian, interesting stuff. And why I never use "water" base finishes.