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Applying the finish is one of the more challenging aspects of lutherie -- not because it's difficult to do but rather because most of us are simply not set up to apply a quality finish. This has been my issue. I have a very small single car garage workshop where I do my most of my work. I have a wood room in my house where I do bracing and keep a lot of my tools. I can do a killer French Polish finish but with the steel string crowd, it just isn't the best option and limits your market.

I used to have Joe White do my work before he retired and he did splendid finish work. I was unsuccessful in finding a replacement and had a negative experience with a well known guitar finisher. In fact, I went to a guitar show right after they did a poor job on my guitars only to find they did some fantastic work for another luthier. Basically, they had some sort of issue with their sealer (my thoughts at least) that cause the finish to settle and shrink back in a bad looking way as well as bad witness lines in noticeable places -- and had the gaul to blame me for the problems. It ended amicably but mostly because I'm a really nice guy -- but underneath I was pissed and this cost me a LOT of money in the long run. Please don't ask who, I don't want any drama and chances are you will have better luck than I did -- but god help you if they screw up because it will be your fault

I didn't try the OLF's Brian Howard, tho' and Tony Ferguson did spectacular work for me before I switched from him to Joe White many years ago. However, I quickly realized that I needed to do my own finish work because my standards are extremely high and I want a very thin finish on the top of my guitars. At this point, I've tried oil varnish and am also done with my first attempt at urethane (it's going extremely well).

I will follow up after the urethane is complete and let you all know if it works or not. After a long 1.5 year journey, spraying urethane is where I have ended up. If it doesn't work out, then I'll go to French Polish. I expect the urethane to work at this point. I believe my concerns and thoughts about finish work might be useful to some of you. In bullet point form, here are some of thoughts/questions that have crossed my mind:


1). I build at the pinnacle of craftmanship. I NEED my finish work to match the rest of my guitars in quality. Not boasting here, I've spent 15 years fervently developing my skills and am OCD to the max. I just want everything to be absolutely perfect or it bothers me to no end.

2). My shop space is small and I don't want to risk my lungs of health. Is French Polish or Varnish my only options?

3). Joe White did a great job with a thin polyester finish (3 to 5 mils max) but my guitars always came back less vibrant. I recently built 2 French Polished topped guitars with Joe's polyester finish on the rest of the guitars -- they were noticeably superior instruments.

4). I believe that on super responsive guitars - the finish becomes more important. I don't think the finish is a massive factor on heavily built factory guitars.

5). I think polyester may be too hard a finish. At least, it does negatively effect the tone of my guitars. It is; however, a superb finish in terms of durability.

6). I haven't delved into much of the waterborne finishes but my early experience with waterborne finishes was kinda "meh". They just never had the depth of solvent based finishes. Aesthetics are extremely important to me. I am also selling guitars at a price point that warrants the quality being the best it can be.

7). I spent some time with Murdoch Uralkyd 500 oil varnish. Beautiful finish and durable but a lot of work due to sanding between each layer. I brushed it on and had issues with it drying over some of the Rosewoods. I also had problems with surface tension and it pulling away from edges. I believe spraying might have helped but ultimately, I would probably need to change headstock and not bevel the edges which was causing my some trouble with the varnish. Ultimately, I found the varnish very finicky. The tone; however, was every bit the equal of French Polish.

8). The oil varnish is very beautiful on certain woods but I dislike the intense amber hue on spruce and maple. The Murdoch is one of the less yelllow varnishes. Also, varnish yellows over time. This is an aesthetic issue for me and one of the major reasons I moved on from Oil Vanrish along with the Rosewood drying issue -- I use Rosewood and Cocobolo ALOT.

9). Nitrocellulose lacquer is easy to apply. It is easy to repair. The burn in also allows makes it a bit easier to go for thinner film thickness without fear of witness lines. Tonally, I feel certain I could get what I need out of nitro and also the looks. Crazing and checking do concern me as does it's reactivity to plastics and certain sweat/chemicals. Customers have become used to more durable finishes.

10). Ultimately, I decided not to do lacquer because of the off-gassing. The catalyzed urethane has very nasty chemicals but they are gone within a day for the most part. I still may consider lacquer but only if I have a shop that is well equipped to handle finish work -- meaning a separate room just for spraying or where I can store the guitars and let them offgas for a month.

11). My homemade spray booth works extremely well. It is capturing all the over spray and eliminating the VOC very quickly. There is some lingering smell in my house from the MEK but it is barely noticeable and is gone fairly quickly. My home is extremely "unsealed" - I can put some acetone outside and smell it inside quite easily -- so I am confident that my booth is doing a good job and that I am not messing with my health. I plan on sharing my spray booth setup as it may be helpful to some of you all. I am completely decked out in protective gear and wear fresh cartridges. I evacuate the air while I'm spraying and also at periodic intervals while the guitars are drying. My shop smells bad but the smell is completely gone a couple days after spraying.


12). My major concern now is whether the urethane will hurt the sound of my guitars. My thoughts thus far are that it won't be quite as good as French Polish or varnish but will be awfully close -- and noticeably better than polyester. But we will see, I still have the final topcoats to apply but I also have to level and sand the finish - so it should be a wash in terms of film thickness at this point.

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That's it for now but I will follow up in about 1 month with my thoughts on the urethane as well as share my spray booth setup and the like. If the urethane works well, then I will share my urethane finishing process. I'm using the Cardinal Luthierthane product, FYI.

Best of Luck to everyone in the New Year. Hopefully, it won't be the dumpster fire that was 2020

Nice post and some things to think about for myself. I'm still using Mohawk instrument lacquer and just step outside my shop to do the spraying and then step back in and hang to dry. Neighbors have never complained but I'm in Canada and not somewhere like California and a very low volume builder. I'm sure some people catch a whiff and think, what the? Interested in trying other solutions, but this still works well for me without a spray booth and haven't had a bug stuck to the finish yet! Sorry for contributing to climate change or whatever.

Thanks for the write up, Simon. Lots of great detail in there.

A question for you - would you expect the Cardinal Luthierthane and their UV cured urethane to behave similarly? I’ve been trying to get my hands on their UV cured urethane in gloss but everywhere I’ve gone I’ve been told it’s sold in 5gallon minimum quantity. I have some of their UV flat urethane but wanted to try the gloss to compare to the Simtec gloss poly topcoat I’m using now.

Hope you are well!

Brad


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I've primarily French Polished for years, with very good results. The past couple of guitars I've done, I used RoyalLac instead of shellac, still applied via French Polish. I like the results. It goes down like shellac does, builds a little quicker. But after a month or so, it's a far harder finish and seems to be a lot more forgiving of sweat, alcohol, etc. over shellac. Time will tell how it does in the long run. It's a little more toxic than shellac, but doesn't seem to be too bad. Still a very thin finish, but probably a bit more durable than conventional FP. That said, my conventional French Polished banjos have been running around the festival scene for years with no complaints (at least that have made it back to me). Pretty tough torture track there.

I too have very limited space--12x20, but I'm going to try spraying RoyalLac on my next project. I can make room for a temporary spray booth. We'll see how it goes.


Dave

I've been French polishing with Royal Lac as well. I like the results and plan to keep using it.

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Steve Smith
"Music is what feelings sound like"

I noticed a pretty big improvement between urethane and polyester applied at more or less the same thickness. The urethane ate less life.

I need to figure out how to FP. My pal gets his back/sides done in UV poly and then FP’s the top in catalyzed Royal Lac and gets a 1.5 mil coat. About as good as you’ll get with a buffed out top coat I imagine...well, he pads it on then sands and buffs so I guess it’s not really FP. But it’s thin..

catalized varnish may be something to look into
thin high gloss not too difficult to use.

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John Hall
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Some really good replies here.

For those of you that have used Royal Lac -- here are my thoughts and potential fears. I too have heard about the improved durability of Royal lac and have considered it. I imagine it is nowhere near the same durability as the Cardinal Urethane but still a finish that would be marketable to the high-end crowd. And that is an issue for me and for many of you here -- we need a finish that is marketable and that doesn't look/function inferior to mass produced guitars.

What happens to Royal Lac if Vijay goes out of business?
What happens if you need to repair the Royal Lac?
Does French Polish (or Royal Lac) go over it? (One of the things I love about French Polish is the ease of repair.)
Can you get witness lines between coats if they are applied many months down the line?

I didn't have answers to those questions and I thought I would give spraying the urethane a chance as it will likely make it easier for me to get a "perfect" finish. Thus far, I like the workability of the Cardinal product very, very much. It goes on well and covers well and seems to have some flexibility to it. I'm just trying to get the top finish extremely thin. I have considered using urethane for everything but the top and either using FP or Royal Lac to get the tone I want. If I go the route of applying Royal Lac then I may be bothering some of you for pearls of wisdom regarding its application.

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HI Brad,
I prefer using the catalyzed stuff because I worried about getting a perfect cure with the UV. The UV stuff is also a bit expensive. From what I understand, the end product will be the same whether UV or chemically catalyzed. Tim McKnight has been very helpful and he uses the McFaddens urethane and likes it. I've never used it but the Cardinal product has given me no reason to try anything else. Bear in mind, I'm not an expert with these modern finishes -- so don't take my comments as fact.

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Hi Ed,
If you ever want to discuss FP - give me a call. I'm not too shabby when it comes to doing a quality French Polish on a guitar.

Your post echos my thoughts and experience. I've been building for eleven years and spraying nitro for forty. Nothing sucks quite as much as OCD'ing your way to a near-perfect build and then having issues with the finish.

My own hands-on experience with finishes is mostly nitro. At this point I can execute a flawless high gloss nitro finish. Over the years I've communicated with dozens of experienced builders and finishers and the consensus is that there is no perfect finish. Some are easy, some are difficult. Some are dangerous and some less so. Some are more durable and some are less. Water based finishes that I have tried just don't cut it.

One of my mentors and a very experienced high end builder told me years ago that the average steel string player isn't responsible enough for a FP finish. I tend to agree after years of dealing with build customers and repair customers. I recently got a call from an out of state number, a guy who found one of my 2018 builds in a consignment shop in Boise, ID. The guy told me that it was one of the best sounding guitars he had ever played but that it was beat to hell. The back was cracked, there were chips, dings, and scratches all over it. This is more typical than the person who cares for an instrument well. FP scratches much too easily for my purposes.

I've settled on nitro as the best combination of all factors for me. I have a 20 x 40 shop with a small built-in spray room. Explosion proof fan that moves a lot of air. I spray full builds May through October and only do repair touchups in the colder months. I time spray sessions on days when I can do work outside of the shop, and I vent the shop with the fan intermittently during the first few days of off gassing. This is not an ideal setup but it works for me and is the best I can do without sending my work out to someone else. I won't do that.

I've seen Brad's finish work and it is gorgeous. So obviously there alternatives to nitro. But none of them are perfect. Pick your poison.

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It will probably be alright.

Simon, No disrespect but do you live out in the boonies, well away from neighbors and kids?

You have hit upon the conundrum: luthiers want their guitars to sound way better than factory guitars but they want them to look like factory guitars and take similar amounts of mishandling. I think this is a Venn diagram where the circles don't intersect.
I have been working with button lac and in my experience it is considerably more durable than blonde. I sound like a broken record but if you look at antique guitars from before the nitro days, anything from CF Martin to Washburn (Lyon & Healy), or pre- and post- synthetic finish classicals that have been finished with shellac you will be amazed at how well the finish has held up. Besides the possibility that various gums might have been added to shellac the biggest elephant in the room is that all shellac used to be processed by heat. Button lac is the only commercially available shellac that is heat processed. Apparently there are still handmade shellacs that are heat processed but I have no idea where they can be obtained. The color of button lac is darker than blonde, which makes finishing a soundboard more difficult, and obviously retouching as well. The most trouble-prone areas on guitars finished with modern shellac are the upper bout on the back's bass side where it comes into contact with the chest, as well as the bass side rim where the arm crosses. Blonde shellac on the soundboard holds up well in terms of moisture resistance, probably because there is no contact per se with the player's body. If you try to get any film to 1-2 mils thickness it will dent easily on the soft soundboard no matter what finish is used.
There are so many advantages to shellac for the hand builder, not the least of which are no special equipment or spray room is required, and the complete absence of health worries for you or your neighborhood. Oh yeah, it is the best for sound.
I am reminded of a lyric in Bob Dylan's "Lay, Lady Lay": Why wait any longer for the one you love when he is standing in front of you?

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I spray nitro and don't see switching to anything else. My spray booth in my attached garage shop pulls makeup air from my house. Off-gassing use to be a problem until I installed a small bathroom vent motor in my spray booth to pull a tiny bit of air. I let it run for at least a week after the last coat. This has made a huge difference and no more complaints from the wifey.

Hi Barry,
Yep - that was my particular issue. The off-gassing would have been a problem for me. I'm still considering nitro but won't really consider it until I have a different shop. Even spraying outside and leaving the guitar in my shop would have been an issue with nitro. For me, this is the appeal of the urethane. As long as I can get good tone out of this, I think the urethane is superior to nitro in every regard, except for looks and repairability. Almost as good looking as nitro and better looking in the long run (I don't like the decayed nitro look) but nowhere near as repairable. Always a tradeoff with finishes - nothing is perfect. One of the appeals of urethane is that it does cure quickly and the finish doesn't continue to shrink -- so if you build a good film and wait a while before buffing -- the urethane can continue to look great indefinitely. The traditional Martin crowd may however, prefer nitro -- so what works best for me might not be best for others or their clientele.

Hi Tom,
I've definitely kept your advice in mind while thinking through all this stuff. Bear in mind, I'm also a proponent of French Polish and skilled at it - so that is definitely a viable option for me.

One of my concerns is that the French Polish is often a surprising element for players - they just aren't accustomed to how delicate it is. At least, that has been my personal experience with my clients. Classical players are a different matter. I also don't want to outsource anymore -- so I'm doing the entire finish myself from here on out. French Polish over the entire guitar has some definite drawbacks. I also vastly prefer the aesthetics of a finish with very little color.

Oil varnish is every bit as good for tone as the shellac. My guitars still sounded impressively good with the polyester. IF I can get very close to the sound of varnish or shellac, then the urethane is a good mix of qualities that works well for me. But we'll see, as I mentioned - I can still just French Polish the top and that may be the best course of action. It really depends on how well I can do the urethane finish on the soundboard.

Regarding the VOC health issue, I am getting very little over spray and very little chemicals into the surrounding area. Urethane is a high solids build - so I don't have to spray much to build up the finish. All over spray is being collected on my booth and not going all over my shop. The main "smell" culprit is MEK - similar but a bit worse than acetone. I live alongside a river -- any smell outside is carried away and dispersed immediately. Any person applying oil paint inside their home or outdoors is probably "polluting" more than I am. The main issue is my health within my shop. There the chemicals are concentrated if I can't disperse them. The main issue for me is the isocyanates in the urethane -- very bad stuff. It is gone the next day but I want most of it out of the shop and certainly not pouring into my home. Overall, I am incredibly health conscious and I feel quite safe with my setup and the urethane. I wouldn't feel safe with nitro in my particular circumstances.

I have taken a lot of my precautions in how I approach spraying -- for anyone that's interested, I will follow up in a few weeks with a write up of how I'm protecting my health and ensuring this stuff doesn't harm me. A haphazard approach is definitely not sensible when spraying either urethane or nitro -- or any finish for that matter.

I don't have much to add as my only finishing experience has been French polish and some waterbased finished applied when I was a teenager but I'm intrigued by your mention of varnish. Have you used a wiped varnish like Liberon finishing oil (used by Kevin Aram) or something more akin to what Bruce Sexauer is using? My shop is very small so as I introduce a steel string model a varnish I can apply without passing out is something I've been very interested in for that project!

Hi Brian,
If you want to use varnish then I recommend using the Ace varnish or the Murdoch Uralkyd 500 varnish. Bruce uses them mixed 50/50 I believe. I brushed the varnish but believe I would have had better success if I sprayed them. The Murdoch is actually quite pleasant to use (until you add acetone) -- but overall, it is an incredibly "healthy" alternative. IF you go that route, feel free to give me a call and I can give you some pointers.

I STRONGLY recommend using a rotisserie setup if you are applying varnish. My main issue with the varnish were as follows:

1). Too amber/yellow for my tastes on spruce/maple. The ambering increases with age. Not too mention that wood darkens with age.
2). Drying issues over Rosewood - in particular Cocobolo.
3). It's a lot of work - having to scuff sand between each coat. Spraying this urethane is so much faster.


You might consider General Finishes EnduroVar. I have heard good things but decided against it.

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For me, if the urethane doesn't work out -- then I will go to French Polish. Nitro was also an option for me but my shop space doesn't permit its use.

I just touched up one of my guitars I built about 3 years ago which was done in Royal Lac. I touched up with regular shellac and a pad, basically French Polish. It looks just fine. That's the wonderful thing about shellac is it stick to anything and can have a nice gloss.

I almost always FP guitars now and mostly with regular shellac. I like the Kusmi button shellac. I will use Royal if a client wants something a bit more durable and resistent to sweat, alcohol etc..

I do like an oil varnish though too.

But anyway just wanted to chime in since you asked about repair. It seems to me that regular shellac touched up Royal pretty well.

Thanks Simon! I had planned to brush as I lack any sort of spraying capabilities (both knowledge and tools/appropriate space to set up a booth) Although the water based finishes I used tended to have some slightly blue coloring in certain light (I've heard this was common with the finish I was using) I generally enjoyed brushing and was able to achieve pretty good results.

The amber tone is a plus for me and considering how sore my arms get after spending a few weeks polishing a guitar the extra work isn't too big a turn off! Mostly concerned about the wear steel strings receive compared to classicals.

Just curious, what kind of brush were you using? I had used foam brushes but would like to try a bristle brush much like violin makers use.

I would not add acetone to the Murdoch varnish; that may contribute to problems you mentioned around the edges. It's thin enough already, unless you're trying to spray it. I ran int something like that once with acetone in the old 'Rock Hard' varnish, when I added a bit too much as the stuff thickened in the can: it 'pulled', like water beading up on a surface with low surface energy.

TRein wrote:
"You have hit upon the conundrum: luthiers want their guitars to sound way better than factory guitars but they want them to look like factory guitars and take similar amounts of mishandling. I think this is a Venn diagram where the circles don't intersect."

I think it's the customers. When I was sharing shop space they used to complain to us that our guitars were not as shiny as the factory ones. It's easy to get that look with a thick finish that eats sound. Ovation has used .04" of epoxy on the tops; it sure does stay level, and you can buff it right up. Sound? Ah, well.... We're charging more, so we have to do better in every respect.

Surface prep becomes a religion.

The long term chemical breakdown of nitro stops me. One molecule out of every six is a high explosive that breaks down eventually, particularly with exposure to light. When it does it releases oxides of nitrogen that react with water vapor to form nitric acid. Nitro is thus considered toxic by museum conservators, and has to be isolated from other displays, along with cellulose acetate, which releases acetic acid. Didn't Martin use acetate bindings at one point?

Yes, varnishes yellow with age, but I consider that less of an issue than the deterioration of nitro. I've also been told by a conservator that polyurethane becomes brittle with age.

I used, and taught, FP for a while. One of my students came back after three or four years and there was hardly a lick of finish on his guitar. Some folks have sweat that eats shellac. Otherwise, what's to not love?

A friend came by the other day with a new guitar he'd made. It had the usual 'veiled' look, and was crazed all over. He's been spraying a water born finish, and was adding a small amount of alcohol to speed up evaporation and cut down on runs. I've seen that same sort of crazing from mixing a little alcohol into epoxy to slow it down. There's a bad idea you can avoid.

I have yet to hear of the 'perfect' finish. Urushi lacquer can be the most beautiful, durable , thin, flexible, and water proof of them all, apparently, but it's related to poison ivy, and some people are quite allergic to it. And so it goes.

Oval soundhole and I were typing at the same time.
I use a soft 1" 'camel hair' brush with oil varnish, but that's just my preference. You can spend some time pulling the Murdoch's varnish I use on, and it's thin enough that getting too much down gives lots of runs, so a small brush works well. It's a 'floor' finish after all, and is not formulated to be applied to vertical surfaces.

Royal Lac is not as repairable as French Polish. Once cured if you need repair you basically need to refinish if you want it perfect. Royal Lac does not bond to fully cured Royal Lac. It does seem to bond to shellac and royal lac bonds to shellac, but you could not do a royal lac or a shellac repair without out witness lines. I use gluboost fill and finish for repairs. They look good and are OK in a repair situation but are not perfect.

All the above has been my experience.

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Thank you, John. That was my suspicion and why I've been hesitant to consider the Royal Lac. In my opinion, one of the most promising features of French Polish is how easy it is to repair.

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Hi Al,
Regarding the acetone -- I didn't add much - at most 5% but maybe that was some of my problem. However, the issue still presented when I didn't add any acetone as well. I think I was laying it down a bit thick with my foam brush - maybe that encouraged the finish to pull somewhat ??? The other issue is that it just wasn't drying on those edges (with Cocobolo). I didn't have as much problem with other tonewoods.

I do know Bruce Sexauer likes to add some acetone as he feels it helps bite into the previous layer and prevent witness lines. Anyway, thanks for letting me know -- very helpful. I liked the varnish a great deal and feel if you can get past some of the application hurdles, that it is terrific finish for steel string guitars.



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I will add that I used foam brushes to apply the Murdoch varnish and it worked extremely well for me. The rotisserie setup also helped prevent any runs whatsoever. The finish laid down absolutely perfect - no sags, no runs, nothing.

Simon--

I'm a dumba** beginner compared to you. Here is a link to a thread I posted regarding my eighth guitar; there are some pics of my first time applying Enduro Var on top of Silver Tip as the pore filler/first layer of finish, both applied with foam brushes (scroll to the bottom):

viewtopic.php?f=10101&t=53753

I think it came out pretty nice. If I can make it work, somebody with your level of expertise would have no problem.

I recently built a knock down spray booth (documented in another thread), because I want to experiment with a few other finishes that are best sprayed. Catalyzed finishes seem to hit a good spot that you might be interested in. They are very toxic while mixing and applying, but after a short cure time, they are relatively harmless. So, no long, smelly off-gassing period.

Unfortunately, if you want the ability to repair the finish, shellac and nitro are the burn-in finishes. All of the more modern options require more skill to apply an invisible repair. But the upside is that repairs are less likely to be needed, because the finishes are more durable in the first place. As has been said, there is no perfect finish.

I can say that, when I take my new spray booth for a spin in a few months (I need to build another guitar first), the first finish I will be experimenting with is Royal Lac Post Cat. When fully cured, it is harder than nitro, but slightly softer than 2K. It looks just like shellac. It stays repairable for several weeks after application. The working solvent is alcohol. There's just a whole lot to like about the finish, from the accounts I have read. I have used the original formula, and I liked French Polishing with it. But I am very interested in this catalyzed version.

Good luck with your quest for a finish that will meet your needs.

HI Don,
I hope you'll chime in when I discuss my spray booth setup (knock down like yours) - that will yield a more helpful thread.

I'm currently using a catalyzed urethane from Cardinal (Luthierthane) - I believe it is used by some major US manufacturers and seems to be a well-regarded product. Please let us all know the catalyzed Royal Lac turns out. I'm still at the stage where I'm considering a few options, especially if I don't get the results I want with the catalyzed urethane.

What I do like about the product thus far is that it has extreme clarity -- builds quickly and is easy to level. I also like that the finish cures quickly and becomes stable quickly. The isolante sealer pops the grain extremely well - epoxy pore filling works great and a Rosewood oil based pore-filler makes Mahogany necks look fantastic. So visually, I'm really happy with this product thus far -- but if I could get most of these results in a less toxic package -- that is certainly worth looking into !!!

I may have to do something like that Barry although the smell doesn't permeate into my living space. I use proper PPE when spraying and maybe I'm a little weird but the off gassing smell doesn't bother me in the days after spraying. Might have something in common with Hunter S. Thompson "There is nothing in the world more helpless and irresponsible and depraved than a man in the depths of an ether binge". Ha! Cheers.

FWIW I sprayed a guitar with Post cat RL it turned out fine, but I still noticed a tone bite even at 3.5mil.

Next time I’ll spray the body and pad the top. The 1.5mil finish on the top is a goal...

And that's not an easy goal to achieve !!! I'm going to try and get under 3mils and hopefully, that will be thin enough to not hurt the tone at all. I also think it is very important to keep the finish thin around the edges of the top - that is home to a lot of higher frequency modes. Ultimately, I want it thin everywhere on the top and equally so. We'll see ....