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Old 08-13-2020, 08:02 PM
seangil seangil is offline
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Default Using Varnish

I've got a steel string, parlor-sized guitar build (spruce top/maple back) that is at a point where I need to add the finish. I don't have access to to a spray booth and had wanted to avoid nitro and highly toxic finishes. I have done a lot of reading in the various forums, pages, etc. and seen a wide range of opinions about different finishes. I'm really struggling with what to do. I had hoped to find a water-based lacquer, but have just seen too much negative feedback to feel comfortable trying it. Tru-oil and French Polish have advantages of being generally low toxic, but my understanding is that they offer pretty limited additional protection and need to be occasionally buffed up.

I am interested in varnish as a possible option. I have read about how it is "softer", but also allows more vibration. It also can be rubbed on. Collings has a good brief description on their site.

My question is less about how to describe the benefits of varnish and to ask:

"Under what circumstances would you choose to use a varnish product (e.g., Waterlox) over a lacquer (e.g., nitro)?"

Appreciate any thoughts.
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Old 08-13-2020, 08:18 PM
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Take a look at Beechwood Casey "Tru-Oil," a classic wipe-on gunstock coating. It's an ideal finish for the inexperienced user, can be applied in multiple coats, cures rather quickly and looks very good. Once cured, it's a good deal more robust than you might imagine for an oil finish.

Practice first, of course. . .
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Old 08-13-2020, 09:13 PM
seangil seangil is offline
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Default Tru-Oil

Thanks Frank. My hesitation about using Tru-Oil:

- My understanding is that it does not provide much additional protection to the wood; and

- It takes a lot of coats.

In your experience, how long does a tru-oil finish last? And under what circumstances is it preferable to varnish?

Sean
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Old 08-13-2020, 10:22 PM
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Mr. Jelly Mr. Jelly is offline
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My experience with varnish is that it's soft not very defined but really cool. For a guitars tone to really come through I'd say varnish is the way to go. After a second thought I agree with myself.
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Old 08-13-2020, 10:47 PM
charles Tauber charles Tauber is online now
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I think you’re barking up the wrong tree. There are many finishes that are viable for a guitar. The best one is specific to your circumstances, the one that best is at the intersection of what you want in appearance, protection, sound and application method that suits your available level of technology and tolerance for tedium.
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Old 08-14-2020, 06:42 AM
seangil seangil is offline
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Default varnish

Hi Charles,

Your post nails my problem exactly - too many choices and not enough context. I've read a lot of posts about different attributes, but most write about finishes like wine tasting - lots of descriptors, but I still don't have a good sense of when to choose one over the other.

In this case, I value:

- Protecting the guitar body for nicks and scratches;
- Low toxicity since I don't have a well-ventilated space to work on this;
- Ease of getting an even finish;
- Glossy, even surface is nice, but not essential in this case, particularly since my woods are pretty smooth;
- Needs to be compatible with a pore filler since I already used one;

If these are not the right type of criteria for eliminating options, then welcome advice from others. I am trying to figure out how to sort through the vast, semi-structured advice on the internet about the many different finishes out there.



Sean
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Old 08-14-2020, 09:25 AM
charles Tauber charles Tauber is online now
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Quote:
Originally Posted by seangil View Post
In this case, I value:

- Protecting the guitar body for nicks and scratches;
- Low toxicity since I don't have a well-ventilated space to work on this;
- Ease of getting an even finish;
- Glossy, even surface is nice, but not essential in this case, particularly since my woods are pretty smooth;
- Needs to be compatible with a pore filler since I already used one;

If these are not the right type of criteria for eliminating options...
Those are exactly the criteria to identify.

Let's start at the top. Finishes applied to wood, generally, fall into two broad categories: penetrating finishes and surface finishes. As the names imply, penetrating finishes are absorbed into the wood while surface finishes have little appreciable absorption and sit on the surface of the wood.

Examples of penetrating finishes include oils such as olive, tung, "Danish", walnut, linseed and others. Generally, they are the easiest to apply - usually a rag or brush - but offer the least protection from moisture, dirt and mechanical damage (abrasion, impact). Although commonly used to finish wooden items, in my opinion, they aren't a good choice for "fine" guitars.

Examples of surface finishes include varnish, lacquer, shellac, urethane, and others. (Though it can be used as a surface finish, I purposely left epoxy out of this discussion: it is different than the usual surface finishes.) Surface finishes can be applied with a rag/pad/trowel, brush or sprayed. (penetrating finishes can also be sprayed but seldom are.) Many of the common surface finishes involve "solids" that are dissolved in some sort of evaporative carrier that makes for a liquid that facilitates application. "Drying" or "curing" is the evaporation of those solvents.

Application of the liquid leaves a texture to the surface film that is applied. That texture is dependent, in part, on the method of application. A brush can leave brush strokes, a rag/pad can leave "drag" marks and a spray can leave a pebble-like texture of the atomized liquid. Regardless of the method of application, the finish, ideally, has sufficient time before becoming sufficiently solid to level and "flow-out" to reduce some of that texture. (French polish, a method of application, involves many very thin smooth coats and doesn't rely on the liquid finish to level.)

Light striking a surface reflects from that surface. The more irregularity to that surface, the more scattered is the reflected light. The more scattered the reflection, the lower the gloss of that surface appears. The less scattered, the shinier/glossier that surface appears. The higher the gloss, the more visually obvious are any imperfections and/or textures in that surface.

While penetrating finishes are typically matte or very low gloss, surface finishes can be at any level of gloss from matte to mirror. Given that the higher the gloss, the more obvious any surface imperfections, a low gloss (matte or satin) finish will hide surface imperfections and the texture of the finish application while a high gloss finish will accentuate them. A "good" high gloss finish requires a "perfect" surface, free of imperfections.

One of the imperfections that high gloss finishes should be free of is texture left from the application method. In many high gloss finishes, the texture left by the application method - brush marks, drag marks or spray gun atomization/drips, runs, etc. - are abraded out using successively fine abrasives, each removing the surface imperfections (abrasion scratches) left by the previous one.

Much of the work in applying a high gloss finish is in achieving the "perfect" surface, eliminating defects in the wood surface, eliminating texture left from the application method and "eliminating" - sufficiently reducing in size - the scratches in the finish due to abrasion of the surface to eliminate texture from the application.
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Old 08-14-2020, 09:26 AM
charles Tauber charles Tauber is online now
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With that background information, lets see how that aligns with your stated values.

- Protecting the guitar body for nicks and scratches

Typical penetrating finishes (and wax) offer the least amount of protection from mechanical damage.

Nearly any of the surface finishes offer some level of protection from mechanical damage. One of the goals in a finish for an acoustic guitar is that the finish not inhibit tone. The best approach to that is a finish that results in a thin film. As a thin film, all of the surface finishes leave the wood susceptible to mechanical damage. Some finishes are harder than others, some are tougher than others, but most will offer "adequate" protection from minor scratches and bumps: none will allow the finished guitar to be used as a baseball bat and remain unscathed.

- Low toxicity since I don't have a well-ventilated space to work on this

Veteran guitar maker Sergie de Jonge once stated that he started out with "solvent-based" lacquers before switching to water-based finishes, only to find that he found the water-based finishes more "toxic" to his health than the solvent based ones. He now uses shellac (French polish), finding it to be the most benign for him. He stated that it typically took him about 15 hours to spray finish a guitar. After sufficient practice, he now French polishes a guitar in about 12 hours. French polish can be done almost anywhere and requires no special equipment. It does require skill.

Tru-oil, a finish I haven't tried, is applied much like a French polish. My understanding is that there isn't a lot of smell/fumes since little actual finishing material is applied - less solvent, less evaporation.

"Varnish" is an umbrella that includes a wide variety of evaporative solids-dissolved-in-solvent liquids. Some are water-based, some not. Traditional varnishes, such as used on violins, evaporate very slowly; more modern ones are more like lacquers - another umbrella term.

In many circumstances, the actual application can be done out of doors. For example, you can spray lacquer outside and then bring it in doors between coats and for curing. It will outgas and smell, when brought indoors, as will many finishes.


- Ease of getting an even finish;

I think I can safely say that no "good" finish is easy. If you want a texture-free, gloss finish that looks "perfect", there is no easy way to achieve that, particularly in a typical hobby workshop environment.

As I previously stated, the lower the gloss, the less obvious the surface imperfections. Getting an even finish is easy for a skilled French polisher, as it is for someone skilled in spraying and who has the right setup and equipment.

For someone new to finishing guitars, a wipe-on finish is probably easiest and involves the least amount of sanding to remove application texture. Finishes such as a wipe-on polyurethane - I've used a wipe-on poly on a variety of furniture projects, though not guitars, and have found it very easy to produce good results, though it smells while drying - shellac or Tru-Oil could be good choices.

- Glossy, even surface is nice, but not essential in this case, particularly since my woods are pretty smooth

That suggests a higher-gloss wipe-on such as shellac or polyurethane or a sprayed finish. You can use aerosol cans of lacquer or urethane sprayed outside. One can produce an acceptable finish with aerosol cans.

I don't believe one can get a high gloss from Tru-Oil.

- Needs to be compatible with a pore filler since I already used one

Just about any surface finish is compatible with pore filling. If need be, a coat of shellac can be used between the filler and the top coat.


If you don't already have spray equipment - or don't plan on buying it - that largely rules out any sprayed finish, unless it is from a can. Choosing to use an aerosol can limits/defines your choices.

That leaves brushing or padding. I've sprayed Target's EM6000 - a water-based "lacquer" - with good success. (It smells bad, though.) One of the makers who used to post here reported successfully brushing it. While varnishes can - and are - sprayed, they are traditionally applied with a brush. Traditional varnishes have a long drying time between coats and an even longer curing time. (Many sprayed lacquers need two to three weeks to cure before polishing: traditional varnishes longer than that.)

French polish is a method of applying shellac with a pad. (It can also be brushed or sprayed.) Tru-Oil is also. I already mentioned wipe-on poly. There are also some padding lacquers: I've used one, who's name escapes me, but it smelled just awful, worse than nitrocellulose lacquer, which is not easy to do.

There is a relatively new class of finishes called "hard wax". They are an easy wipe-on finish. I've seen it used on a guitar. It wouldn't be my first choice, but it is a viable finish. It is lower gloss. One hard wax line of products is from a company called Osmo. That finish was discussed on this forum a month or two ago.

Also recently discussed here is a new product line of UV-cured lacquer-like products by Solarez: https://www.solarez.com. I have not tried them, though I'm curious about them and will likely try it at some point. Bruce, I believe, mentioned that their product is brittle. That could be a viable finish option.


In the search for the perfect guitar finish, I've chased my own tail on choice of finishes for four decades. There are new finishes being introduced - and some that are retired - on a regular basis. There are many options. A lot of trial and error is involved, both in finish type, brand and application method. I tried Target's EM7000 - it was a disaster - but their EM6000 worked very well. (EM7000 has since been retired and is no longer manufactured.)

What I've learned over the years is that many, many finishes can viably be used on a guitar - not just the ones used by the large guitar manufactuers in industrial settings. My advice is don't deliberate too much, just chose one and start learning how to make that one work. No matter what you chose, practice on scrap, not your completed guitar.
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Old 08-14-2020, 09:39 AM
Alan Carruth Alan Carruth is offline
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"In this case, I value:

- Protecting the guitar body for nicks and scratches;
- Low toxicity since I don't have a well-ventilated space to work on this;
- Ease of getting an even finish;
- Glossy, even surface is nice, but not essential in this case, particularly since my woods are pretty smooth;
- Needs to be compatible with a pore filler since I already used one;"

I can't think of any finish that does all of those things, and that's going to be the case pretty generally, no matter what your wish list is. As a friend of mine says; when there are a lot of different ways to do something it's a sign that either everything works, or nothing does. Finishes are an example of the latter.

To protect the wood from nicks and scratches you will need a fair thickness of tough and hard finish.Tough and hard are attributes that don't often go together: nitro is fairly hard as modern finishes go but not all that tough, in the sense that it scratches, and this is often the case with solvent based resins. Shellac is a solvent based resin that is fairly tough, due to the fact that it's naturally cross linked, but it's not as hard as nitro. French polish is a method of applying shellac (or other such resins or mixtures) that gives the thinnest possible coating, which is why it has about the least effect on sound. You can brush shellac to get a thicker film that will wear better.Be aware, though, that shellac is soluble in alkaline water solutions as well as alcohol, and some folks seem to have alkaline sweat. There are some oil-resin varnishes that are both hard and tough; look for floor finishes, and avoid 'spar' varnishes: they have a lot of oil in them which makes them soft.

Note that any finish that has oil in it adds damping in proportion to the amount of oil. This tends to kill highs. Thicker finishes also can kill high end sound due to the added mass. Oils that soak in also add a lot of mass. Tru-Oil doesn't seem to soak in as much, and may form a better protective film than plain 'boiled linseed oil'. But oils don't cure hard, so they don't offer much protection against dings and scratches. They are easy to renew once the damage has happened.

This sort of dissection could go on all day, and leave you just as confused in the evening as you were in the morning. That's why I say that there is no 'good' finish.

The only person who can cut the knot is you. Dig out all the scraps of the wood you used to make the guitar and make up sample coupons. Get three or four different candidate finishes and try them out on the samples to see how they work. Choose the one that has features you need and drawbacks you can live with. If I were you I'd try Tru-Oil, shellac (Zinnser's is easy to get and usually pretty good), and one or two varnishes. Some luthiers have reported good results with Pratt & Lambert #38, now put out by Sherwin Williams, iirc. I've been using Murdoch's 'Ure-alkyd 500' floor varnish, from Sutherland-Welles. It's relatively environmentally friendly (the resin is made from the waste from a cheese factory, and they use citrus solvent rather than mineral spirits as a thinner), hard and tough, and it goes on thin. It can also be a bear to get it to harden on some tropical woods, ad with the hardness it takes some work to polish up.
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Old 08-14-2020, 09:40 AM
CaffeinatedOne CaffeinatedOne is offline
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Might want to investigate a wipe on poly finish - again, there are many brands and so forth, but Stew Mack, Allied (I believe) and LMI have all experimented with versions of these finishes and offer products that would work well. As with any finish, surface preparation will be 99% of the work involved.
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Old 08-14-2020, 12:44 PM
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One of our old-time luthier pals said, "It shouldn't be called "finishing" - it should be called "beginning". . .
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Old 08-14-2020, 12:53 PM
seangil seangil is offline
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Default waterlox?

Many thanks to everyone - particularly Charles and Alan for laying out so much in a systematic way.

I am going to pick up a varnish product for a test run. Has anyone use Waterlox? I don't know that I can find Murdoch's around me.

I have used the solarez pore filler and can post some pictures of a mahogany neck if that would interest people. It comes as a pretty viscous liquid, perhaps akin to the consistency of honey. I used a brush and then a credit card as a wiper/scraper. With a bit of care, I found it fairly easy to get a smooth layer without obvious application marks. VOC smell was pretty strong, so you would need equipment/environment where you can manage that. It cured in sunlight in a few minutes. I have some of the lacquer product, but have held back from using it so far due to some of the reports on it being difficult to level and relatively brittle. However, it does live up to its promise of easy and rapid curing when exposed to sunlight.
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Old 08-14-2020, 12:56 PM
seangil seangil is offline
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Default Osmo

Btw - for those who like exploring finishes, I have one other to share:

https://osmo-store.com/

Mule resonator guitars use them on the neck and I have seen videos from a Canadian luthier using it on his necks. The effect on Mule guitars is quite impressive visually and the neck feels very smooth (although that is obviously more than just the finish).

I haven't found examples of people using it beyond the necks, although I assume that you must also be able to use it on the back/sides if not also the top.

Sean
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Old 08-14-2020, 01:09 PM
redir redir is offline
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The word varnish is complicated too. Tru-Oil is more or less a varnish. I've tried some oil varnishes out of the can before and they are not any more protective then Tru-Oil and probably not with shellac either. The only finish that offers a good nick protection is UV cured Poly.

If you want the best tone imho then you almost really want the least protective finish.
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Old 08-14-2020, 01:40 PM
Rudy4 Rudy4 is offline
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Quote:
Originally Posted by seangil View Post
Btw - for those who like exploring finishes, I have one other to share:

https://osmo-store.com/

Mule resonator guitars use them on the neck and I have seen videos from a Canadian luthier using it on his necks. The effect on Mule guitars is quite impressive visually and the neck feels very smooth (although that is obviously more than just the finish).

I haven't found examples of people using it beyond the necks, although I assume that you must also be able to use it on the back/sides if not also the top.

Sean
I've been using Osmo Poly-x for necks with great results.

To the OP:

Check out my fairly recent mahogany size 0 in the AGF topic:

https://www.acousticguitarforum.com/...d.php?t=578582

Tru-oil is a good treatment for inexperianced users, but I'd advise against it because it takes WAY too many coats to achieve a build up, and it isn't as protective as I'd advise.

I've been using Minwax satin wipe-on poly (NOT the water-based type!!!) for years and have finished many instruments with it. I make up my own "fads" from soft lint-free cotton and apply 3 coats over 24 hours. I'll post a bass building topic that outlines the process. I used the same finish on over a hundred custom lap steels and the results were always quite good.

Here's a bass construction topic on Talkbass outlining the process with photo and text #110:

https://www.talkbass.com/threads/30%...1251494/page-4

Here's the text from that topic post:

110. The body components get another of my favorite treatments, Minwax Wipe-on Satin Poly applied with a soft cotton "fad". For those unfamiliar with the term "fad", it is the common name for the pad that is used to apply the finish when "french polishing". I make them by wrapping a small wadded-up ball of cotton fabric with a smooth layer of the same fabric and tieing up the top with a rubber band. A lint-free soft cotton material is best; I like to use old worn-out tee shirts. I make up a fresh fad for each application and try to be meticulous about applying it in a clean and dust-free method, to the extreme of taking a shower and donning clean clothes before a new coat of finish is applied. An ounce of prevention is worth two or three pounds of cure when it comes to finish application. I do three coats with a day between applications and knock down any dust specks on the surface with 0000 steel wool before the next coat. A wipe-down with a tack cloth proceeds any finish being applied, obviously. When finish is done it's time to once again re-assemble everything and finish up by attending to the wiring details.

Last edited by Rudy4; 08-14-2020 at 01:48 PM.
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