Official Luthiers Forum!

I have a few general questions...

What is the schedule as it pertains to guitars as opposed to cabinets floors etc?

Will varnish stick to a CA porefill, or would I need to add a shellac tiecoat?

Thanks...

For varnish, I've usually done it more or less like this: http://www.cumpiano.com/Home/Articles/A ... acher.html
However, I prefer to thin the last coat with (real) turpentine, as it greatly improves flow out. It's an old school trick, but a good one.

I've found that long term adhesion and durability is better if the shellac sealer coat is skipped, and thinned varnish is used for 'sealer' instead. This does make sink back into the grain more of an issue.

Eons ago, I refinished a guitar with brushed on lacquer following C&N's instructions. I'll never do it again. Very inefficient, a general pain, and takes forever. Lacquer is not meant to be brushed.

Never used CA for pore fill, so I can't help you there.

Al Carruth is the expert on brushing varnish. I've only done one brushed varnish finish and one brushed lacquer finish. I will continue to brush varnish finishes, one was enough for lacquer. I've got Al's finish schedule somewhere, he's posted it here before, but it's for the old Rockhard that is no longer available.
Maybe Mr. Carruth has completed his testing for a replacement for the Rockhard and will chime in. I believe he was looking at several alternatives, P&L 38 is the one that come to mind.
I've put TruOil over a CA pore fill, and that worked fine. I'm not sure that has any relevance to varnish over CA, I believe I'd test that on scrap with the actual products(both varnish and CA) and wood to be used.

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A man hears what he wants to hear, and disreguards the rest. Paul Simon

I have built 20 fiddles, 7 guitars, 1 carved upright bass and one mandolin. All were finished with oil varnish. I start with a resin sealer that is easy to make. Followed by thin coats of varnish applied appx. every 3-4 days, scuff sanded between coats. Usually 7 or 8 coats. Let the instrument sit for a couple weeks, wet sand and level. Let it dry overnight and apply your last finish coat. Let it sit about a week then wet sand up to 12000 grit micromesh and polish. This seems to take a long time. You could probably cut down the time schedule but, hey, what's the hurry? When filling wood with pores like mahogany or walnut, I apply what I call glop or heavy coats of varnish, let it dry and sand back to bare wood and keep repeating until you have a level surface with no pores. Oil varnish is time consuming and takes practice and experience to get good results. But is, in my humble opinion,the best finish for stringed instruments. There are volumes and volumes written on this very subject, so read everything you can find. Ultimately you will have to find what works best for YOU. Not the guy down the street. If you would like more info on MY approach to brushing oil varnish, feel free to PM me. Pals, Vic.

I brush lacquer. Made a video of it. Wanna see it? Here it go
https://www.youtube.com/watch?v=CT5JHBkpd1U

I use Z-Poxy as a pore filler. Never tried CA, but I would imagine there could be issues with adhesion.

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http://www.CostaGuitars.com
PMoMC

Thanks everyone!

Hey Tony,

Thanks for the vid! That is what I have planned for my first one, once I get the neck angle / humidity stuff sorted out. I have purchased the Deft already, but what brand thinner do you use?

Thanks,

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Phil

http://www.oleninstruments.com

"Those who tilt at windmills are only considered insane by those who can't see the dragon."

Tony, is that a goat hair brush?

Goat hair is good for Shellac, not so good for Oil. Maybe OK if you give it a military style hair cut. . .

Personally I think Oil Varnish is one of the easiest finishes to apply. The one major enemy is DUST. Get rid of the dust problem (or most of it) and it makes life a lot easier. I can apply two coats in a long day but I do have a UV cabinet. It's not much of one, I only use one single 2 ft tube. It's enough to dry the varnish in around 9 hours. If I switched on the other tube it would take less than 5 hours. I don't let the previous coat get too dry/hard. All the coats (around 7 or 8) have to go on within a 3 day period. I don't scuff sand or rub down unless I have to i.e. dust nibs. Mostly I can get away without but I have a pretty strict procedure to prevent the dust. With all the prep it takes around 25 minutes per coat. Neck is done separately. All in it's a long days work, around 10 hours in total. Like all finishes, any pore filling has to be complete. You can fill with Oil varnish but you really are extending your efforts and time. A good pore fill helps enormously.

No problem. Happy to help. I use the brand they sell at Lowes. Nothing fancy.



I would not use anything less than the finest hair from virgin, baby goat fetuses. The process of harvesting the hair does not harm the brush maker at all.

Seriously though, it is a natural bristle brush. Probably boar's hair. The solvents in the nitro melt everything else which contaminates your finish and will likely lead to problems down the road.

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http://www.CostaGuitars.com
PMoMC

I'm not sure I'm an exxpert, but I've finally gotten to where I can get pretty reasonable results with a varnish. The problem is that they discontinued it! The story of my life... My understanding is that P&L was bought out by Sherwin-Williams, and #38 was discontinued too.

At the moment I'm liking the Murdoch's Ure-Alkyd 500 Floor finish from Sutherland-Welles. It's pretty new, so maybe they won't discontinue it just yet. It works pretty well right out of the can. I use a small 1" camel hair brush, but whatever works for you works. The main things I pay attention to are keeping the film level, with no runs or sags, avoiding dust, and trying to keep 'sand' down.

'Sand' looks like dust, but it's actually little particles of varnish from the brush. You'll have it the second time you use the brush. There's probably no way to get rid of it entirely, but doing a super job of brush cleaning helps. I wash it out, starting with thinner. DON'T swish the brush around in the thinner; that just gets varnish into solution. Squeeze the brush out as dry as you can. DIP it into the thinner, and squeeze it out again. Keep doing that until you've got as much varnish out as you think you can. I use about a table spoon of thinner to clean my 1" brush. Then I clean the thinner out with acetone the same way. After that, I wash the brush with Ivory soap and water, until I can work up a nice lather with only a touch of soap. I learned this from a student who is an artist, and has brushes that cost a couple of hundred dollars - each.

Again, 'varnish' is a class of materials, not some tightly defined thing. There's a lot of variation between different oil-resin varnishes, and it's likely that each one will require some different techniques to apply well. I concur with Vic that a good oil-resin varnish is probably the best possible finish for an instrument. Just don't think you'll ever find the 'perfect' one: there is no such thing. It's been said that, when there are lots of ways of doing something, that's a sign that either everything works, or that nothing does. Every finish has drawbacks, so I think this is one of those cases where nothing works as well as anybody would like.

Except handing it off to Joe White...

Like Alan, 'sand' is one of the main problems I've had brushing varnish. Complicating the issue is the fact that it's cumulative -- each coat has more sand than the coat preceding it. That makes it especially tough to level and rub out the finish without sanding through to an underlying coat and exposing witness lines. On my last guitar I finally gave up trying to keep my brush clean. Instead, I brushed the first half dozen coats or so with disposable foam brushes. While not nearly as good as a decent bristle brush, they're a lot cheaper. The final coat was done as well as I could using a fresh, 2" bristle. Wasteful, but it worked.

Thanks for the tips on cleaning brushes, Alan. I'll given them a try.

I don't clean my brush until all the coats are on the Guitar. Between coats it's given a quick dip in solvent and then suspended in Paraffin (probably something else in the US). I quickly tired of cleaning the brush after each and every coat. It's amazing how long it takes to clean a brush to the level where you stop getting the 'stuff' from the bristles up by the ferrule.
You also have to watch the soundhole and your own clothes. Both major sources of dust. The bottle/tin that the varnish comes in - the semi dried varnish around the edges can also contaminate. As soon as I pour a measure of varnish out I wipe the edge of the tin/bottle and immediately replace the lid. It's impossible for me to varnish in the workshop. I use the most dust free room I have, the bathroom. 10 minutes before I put a coat on I run the shower hot for a few minutes. Either that or go around spritzing the air with warm water. I use a micro fibre cloth to wipe down the Guitar. It kind of acts like a tack cloth without leaving lint etc. After use everything is immediately stored in plastic snap lid containers - tack cloths, solvent wiping cloth, varnish bottle and the jar top that I use to pour the varnish into. It's all a bit of a regime but less effort than it sounds. All designed to minimise airborne dust.

Michael N wrote:
"Between coats it's given a quick dip in solvent and then suspended in Paraffin (probably something else in the US)."

Kerosene.

I tried that, and ended up with solid brushes.

When you think about it, those particles of 'sand' are just varnish; they're not dirt or brush hairs. I don't worry too much about them, simply knocking off the tops when I sand between coats with #400 paper dry.

The sand problem was greatly reduced for me when I started using those brush spinners, most effective with the brush loaded with thinner. Flushes that stuff right out.

Pat

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formerly known around here as burbank
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http://www.patfosterguitars.com

I got the same when I left it for over a full day. I think the difference is that I don't leave it suspended for much more than 10 hours, so my coats are going on fast. I'm also using an old fashioned Oil varnish without added driers.

Wait, varnish will give witness lines if you sand or buff through coats? Due to the thinness of any given single coat, isn't it nearly impossible to have different coat layers exposed?

My witness lines, if I get them, disappear after a good cure and a power buffing. Hand buffing won't do it. Also, beware using acetone and foam brushes. The brushes will release enough dissolved material to contaminate the varnish, causing fisheyes. This I know.

Pat

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formerly known around here as burbank
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http://www.patfosterguitars.com

Witness lines seem to be due to one or the other of two things: poor bonding or uneven hardness.

Since oil-resin varnishes cure by an oxidation reaction they tend to harden from the top down. It takes months for most of them to harden fully, so normally you're ending up with a succession of 'strata' that are harder on top and softer underneath. As you sand through layers the harder parts polish up better, and those are witness lines. If this is the issue the solution is to put new coats on as soon as possible after the older ones, and to allow as much time as you can after putting on the last coat before you level sand and buff up. It's also possible that the addition of a small amount of an aggressive solvent, such as acetone, can help the new coats to 'bite'.

Waiting too long between coats will also cause witness lines. The surface (which hardens faster) finishes curing, and thus has low 'surface energy': there are no open bonds for the next coat to grab onto. The cure for that (aside from not going on vacation in the middle of putting on finish) is to thoroughly sand each coat before putting on the next one. I use #400 dry sandpaper (tan colored, not the black wet & dry) and make certain to scuff the whole surface. Wet sanding, in my experience, almost seems to 'seal off' the surface, so that the next coat bonds particularly poorly. Thus, if you go through when wet sanding, you need to dry sand very thoroughly before putting on more coats to build up.

Susceptibility to witness lines varies between different varnishes, with the more modern ones seeming to be more prone to this.

I'm getting the feeling that this isn't my finish solution....

There are no finish solutions, only finish options.

What Michael said. As I wrote before:
" I concur with Vic that a good oil-resin varnish is probably the best possible finish for an instrument. Just don't think you'll ever find the 'perfect' one: there is no such thing. It's been said that, when there are lots of ways of doing something, that's a sign that either everything works, or that nothing does. Every finish has drawbacks, so I think this is one of those cases where nothing works as well as anybody would like."

You won't find a 'perfect' finish. The best you can do is find one that has good qualities you want, and bad ones you can live with.