Finishes

davismanLV

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Just because Al likes to talk about finishes SO MUCH.... I'll repeat this post: (although I know he'll debate it to death because he's still talking about it 3 pages later, but.... it bears repeating, I guess)

When you use the term "varnish," you're probably referring to conversion varnish if you spray finishes. If you brush or wipe, you're probably referring to one of the many varnishes sold at home centers and paint stores.

Conversion varnish, also called "catalyzed varnish," dries fast, so it almost has to be sprayed. The other varnishes dry very slowly, so it doesn't make much sense to spray them when you could instead use lacquer or a catalyzed finish and avoid dust and runs.

Though the various products that go by the name "varnish" may seem very different, there's actually a logic to the naming: They all dry hard and cross-link as they cure to produce an exceptionally protective and durable film.

Contrast varnish with oil, which doesn't dry hard, and with shellac, lacquer and most water-based finishes, which don't cross-link. Though you are losing the benefit of easier repair with a varnish, you are gaining much better resistance to moisture, scratches, heat, solvents and chemicals.

Let's look at each of the varnishes:

Conversion varnish is a fast-drying finish that comes in two parts: the finish and an acid catalyst you add to the finish just before spraying. The catalyst brings about the cross-linking. Conversion varnish is rarely available in paint stores or home centers. It's usually found only through specialized distributors or directly from manufacturers.

This is largely because it is a very "unfriendly" finish for non-professionals. In addition to knowing how to spray and tune and clean a spray gun, you have to be precise in the mixing of the two parts and accurate in the thickness of the coats you apply because too thick of a film (more than five mils) is likely to crack.

You also have to work in warm temperatures and have a good spray booth that exhausts all the overspray. In winter months, this means having adequate heated replacement air, which can be expensive to install and operate.

Moreover, despite following all the "rules" for applying the finish, things can (and often do) still go wrong, with the most common being wrinkling and poor bonding.

In return for all these negatives, you get an attractive and extremely durable result. This is the reason conversion varnish is commonly used on cabinets and office furniture, which have to stand up to a lot of abuse.

Alkyd varnish is the common varnish available at paint stores and home centers. It is meant for interior use and is made with alkyd resin and usually modified soybean oil, rather than linseed oil or tung oil, to reduce yellowing. Some varnishes are made with phenolic resin, but these are rare because phenolic resin yellows significantly more than alkyd resin.

Polyurethane varnish is a more recent type of varnish, originally marketed just for floors. But it is more common in stores now than alkyd varnish. It is made with both alkyd and polyurethane resins (more properly called "uralkyd"), and it is usually made with modified soybean oil so there is relatively little yellowing. Polyurethane varnish is more protective and durable than all the other varnishes except conversion varnish.

Spar varnish is meant for exterior use and is made with a higher ratio of oil to resin than interior varnish. This makes it more flexible to withstand the greater wood movement outdoors.

Marine (boat) varnish is spar varnish with ultraviolet-light absorbers added to resist penetration by UV rays. Many marine varnishes are made with phenolic or polyurethane resin and tung oil because these provide the best resistance to water.

There is a big difference in the amount of UV absorbers added to products labeled or marketed as "marine" varnish. The products sold in home centers and most paint stores have very little absorber added, so they are only a little more effective against sunlight than common spar varnish. The marine varnishes sold in boat marinas are far more effective against UV light. They are also more expensive.

Wiping varnish is a term I coined about 20 years ago to categorize a group of finishes that are sold under different names, but are all the same - alkyd or polyurethane varnish thinned about half with mineral spirits so they are easy to wipe on and off wood. This finish is the most popular wood finish with amateurs because of its ease of application and excellent protective, durable, and dust- and run-free results.

Examples of commercial brands of wiping varnish are Wipe-On Poly, Seal-a-Cell, Waterlox, Profin and most brands of "tung oil" not specifically labeled 100 percent tung oil. If you're not sure what you're buying, just make your own by thinning any commercial brand of alkyd or polyurethane varnish. Add less than half thinner to achieve more build per coat. Add more than half thinner to improve flow and leveling.

Salad bowl finish has had a long run as a popular finish, especially with wood turners, because of 20 years of fear created in woodworking magazines regarding the safety of clear finishes from which to eat off. In fact, salad bowl finish is simply wiping varnish made with the same ingredients - including metallic driers - that are included in all varnishes. The implication in the name that other finishes aren't safe has merely reinforced the misunderstanding created by the magazine articles.

Wood conditioner (or "stain controller") is the varnish equivalent of a nitrocellulose or vinyl-sealer washcoat you may use to reduce blotching or within multistep finishes to separate coloring steps. Wood conditioner is varnish-thinned with about two parts mineral spirits to produce approximately the same 10 percent solids content you might use for washcoats.

Unfortunately, it has become commonplace to think of wood conditioner as necessary to somehow "condition" the wood and this has led to its overuse among amateurs. Also, unfortunately, directions on the cans to apply a stain within two hours lead to unsatisfactory results because the thinned varnish has to be allowed to dry thoroughly to be effective. This usually requires six to eight hours.

Gel varnish is alkyd or polyurethane varnish made into a thick gel consistency similar to clear glaze so it doesn't run on vertical surfaces. Because gel varnish doesn't level on its own, most or all of the excess has to be wiped off after each application to get a level result. In this sense, gel varnish is similar to wiping varnish, but with the difference that gel varnish produces a satin sheen, while wiping varnish produces a gloss.

Because gel varnish is less resistant to water than wiping varnish, it's often wise to apply several coats of wiping varnish before finally achieving the satin sheen with topcoats of gel varnish. Apply the gel varnish after steel-wooling the wiping varnish to remove the gloss.

There are significant differences in the varnishes listed, but they all have one thing in common: they all cross-link to produce a hard, durable film that can be built up in several coats to be very resistant to moisture penetration.

This is from a website by a guy called Bob Flexner called "Understanding Wood Finishing". I find it helpful to understand what's going on.

P.s. - nitro is an okay finish for guitars. Not so much for cars. Water will ruin it..... as will alcohol and lots of other things. It's just easy to use and repair.
 

adorshki

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Kind of appropriately coming "full circle"; Clydetower just posted this, straight from the horse's mouth, from here:
http://www.letstalkguild.com/ltg/showthread.php?196076-My-review-of-the-NEW-OXNARD-F55e
Still doesn't tell us WTH conversion varnish is, but it tells us how they're achieving the HG.
THANK YOU Clyde!
Also, I have some detailed information from the finishing manager about the finish on the F55 burst:
The whole finish with color is about 0.9mm total thickness and is comprised of a conversion varnish as a base coat and a nitro top coat. This is similar to how Gibson finishes their guitars to speed up the drying process. In the case of the sunburst finish, the color is under the base coat. For reference, they use Mcfadden EL3128 dark salem for color match.
 
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hansmoust

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Nuuska

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Hello

0,9mm is THICK layer of laquer. Many car parts are made of 1mm steel sheet.
 

bluesypicky

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Now it would be interesting to measure the sustain duration with that kind of coating on the top... (that's if can hear a sound at all) lmao
 

ClydeTower

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tommym

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I corresponded with a few luthiers and guitar companies regarding touching up / color matching old failing nitro finishes vs striping / refinishing the entire guitar. Either way it seems you take a chance. This was my takeaway from all the discussions:

1. There is no guarantee that the new sealers and nitro formulas are compatible with the older vintage sealers and nitro formulas.

2. There is no guarantee that after stripping and sanding the old stuff off that you will be left with enough wood thickness to justify completing the project.

3. There is no guarantee that the new sealers and nitro formulas are compatible with the new sealers and nitro formulas. Man, you just can't win.

Also, with my Guild F44, I was told that there was a possibility that the OHSC itself was deteriorating and contributing to the on-going failure of the guitar finish. The red flag to the luthier was my observation that the nickle plated tuners were fully tarnished after setting in the case for a month or two. I think he was right, as my other guitars with their nickle plated hardware don't have this issue.

Tommy
 

davismanLV

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2. There is no guarantee that after stripping and sanding the old stuff off that you will be left with enough wood thickness to justify completing the project.
Okay here's a problem. Modern strippers, while harsh and volatile, will strip a finish quickly and you can scrape it off (the finish) and then you neutralize the stripper. The wood was already finish sanded to prepare for finish. So unless you use a BELT SANDER.... you can do a light sanding, do a spit coat, and then refinish or stain and refinish if you like. Strippers do not eat wood away...... at least, not any I have used. So, I disagree......
 

adorshki

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Just thought I would highlight the most interesting aspects of your post Tom.
Always a lot to learn on LTG. Thank you.
After all that I can't believe you missed the part about the spit coat.
Consider this a severe tongue-lashing.

Okay here's a problem. Modern strippers, while harsh and volatile, will strip a finish quickly and you can scrape it off (the finish) and then you neutralize the stripper.
Joking aside, what about Polly, er, poly?
 
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bobouz

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Also, with my Guild F44, I was told that there was a possibility that the OHSC itself was deteriorating and contributing to the on-going failure of the guitar finish. The red flag to the luthier was my observation that the nickle plated tuners were fully tarnished after setting in the case for a month or two. I think he was right, as my other guitars with their nickle plated hardware don't have this issue.
A bit of a veer: Quite some time ago, I had an issue with rapid tarnishing re the nickel plating on one of my electrics. If polished, the metal would become hazy again within a week. As an experiment, I moved the guitar into an SKB-type thermoplastic case. Lo & behold, no more quick tarnishing.

Since then, I've sold all my older vintage cases, and converted to the SKB style for a good portion of my instruments. This has also eliminated mildew issues with some of these moldy-oldies. The plastic cases seem to provide a significantly more stable environment overall, and luckily, I really don't care one whit about the originality of cases.
 

adorshki

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A bit of a veer: Quite some time ago, I had an issue with rapid tarnishing re the nickel plating on one of my electrics. If polished, the metal would become hazy again within a week. As an experiment, I moved the guitar into an SKB-type thermoplastic case. Lo & behold, no more quick tarnishing.
I think it's quite appropriate here.
We've had at least 4 or 5 reports of mysterious finish breakdowns over the years and they seemed to be related to "vintage" (including original) cases.
I'm pretty well convinced now that the culprit is the expanding foam that came into widespread use in the early '80's.
With out linking to the several sites I looked at tying to confirm my suspicion that the foam was emitting NCL solvents as it outgassed as it aged, I'll just say my guess appears to be confirmed.
One site states it emits benzene and toluene as it degrades chemically, and those are NCL solvents.
I think the formulations or specific product used as cushioning in the cases has been changed over the years or I'd be seeing the effects on my own beloved guitars which are always stored in their OHC's.
Edit on 5/14: It occurred to me over the weekend that even the glue used for the lining could be the culprit and/or even possibly aggravate the problem.
 
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tommym

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Yeah, when you add the cost of a new custom case to the cost of a complete refinish, plus turn-around shipping, insurance, etc., it adds up pretty fast! For my F44, that would have been the time to do a neck reset, along with a complete refret too. Yep, it adds up pretty fast. The costs were approaching, possible exceeding the cost of a comparable brand new Collings SJ Maple. My NH F-30R and F-30 Standards also threw a wrench in the works by being so much easier for me to play than the narrower 1 11/16" vintage Westerlys which includes the F44. So, I don't see any new vintage Westerlys coming my way in the future. Kind of a sad day when you come to that realization as for me it was always Westerly or nothing when it came to guitars. But sore joints and aging have a way of changing our plans.

Hopefully the "finishes" on my New Hartford Standards will stand the test of time, as they were supposedly a "work in progress". NH started out with a gloss body / gloss neck, then went over to gloss body / satin neck, then went over to satin body / satin neck. I'm not much of a fan of a satin body finish, but I've come to much prefer the satin neck finish on my NH Standards over a gloss finish on the neck.

Tommy
 

walrus

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Thank you for the "stripper" summary, bluesy, I concur that was very interesting. And I assume Tom knows his stuff regarding strippers, being as he is in Vegas.

Still LMAO! :anonymous:

walrus
 

adorshki

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Just ran into this courtesy of SFIV1967.
Gonna post it here because it's about finishes used in Westerly, and the question comes up occasionally:
Was "poly" (in any sense of the term) ever used by Guild?
Why yes, yes it was indeed.
From here:
http://www.letstalkguild.com/ltg/showthread.php?197915-D25-M-what-is-the-body-finish :

Just for the "Well I'll be darned" factor, they actually did use poly on at least one of the "faux soundhole" models in the '80's*, and there's one member who insists his late '90's D4 with satin finish is poly as well.
Although I was extremely skeptical at first, after doing a bit of research into it, I found evidence that seemed to confirm it.
For example, pickguard mounting technique seems to corroborate it: another member removed the p/g on his D4 with simple heat, which wasn't possible on NCL-finished guitars because the 'guards were finished over.

*That came from Hans who corrected me when a new member asked the same question about one of 'em a while back.
One of those scenarios where I've forgotten the detail of the model, but not the fact of Westerly actually having used a poly finish.
Hans also mentioned once they "experimented" with poly in Westerly, and I suspect more than one if not all of those "FS" and "DS" models used poly:
Kurt' got a couple of 'em:
Crossroads.JPG

In fact I think it was the FS46ce (on the left) that Hans ID'd as having poly finish.
Corona Savoy electrics used poly too.
You can be forgiven for forgetting about these very unusual exceptions, if you ever even knew about 'em.
:friendly_wink:
Hideglue, who worked in Westerly said: "There was plenty of polyurethane sprayed in Westerly (solidbodies and archtops)".
See: http://letstalkguild.com/ltg/showthread.php?169130-Lacquer-amp-Poly-What-years

But "poly" is not one thing but multiple things. Polyester is resin based and therefore thicker & goopier. (In general not great for resonance-tone). Polyurethane is more expensive but it's thinner and sounds measurably better than Polyester. But that is what it was in the past.

Taylor for instance is using both. On the gloss models they use ultraviolet-cured polyester (which nowadays is thinner than nitro!) but on satin models they use a base coat of UV-cured polyester and the final satin finish material is a two-part (resin and hardener) polyurethane.

Hideglue also said in the past: "Guild regularly used polyurethane as a finish for quite a few solid, semi-solid and archtop models. The experimentation, and subsequent lack of implementation, was with a UV cured finish, ala Taylor."

Ralf
 
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Br1ck

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Just an FYI. I just built a mandolin and used a new type of shellac marketed as Royal Lac. LMI has some videos on it. I've done a lot of nitro laquer finishes but wanted something a little less glossy. The Royal Lac really fits the bill. I whipped on the sealer and first couple of top coats and french polished the rest.

If I were looking to refin and old Guild, I'd use this finish.
 
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