Official Luthiers Forum!

Man, there`s lotsa info lately on finishes! My question is in regards to danish tung oil. I`ve looked in the archives on this, and read that the tung oil is applied after a sealer coat of shellac. Why? Wouldn`t that hinder the oil penetrating into the wood for a constant color or hue overall?

_________________
Give me 50 cents worth of regular.
Check my oil too, if you don`t mind,,,

I think the oil will penetrate too deeply without the shellac. Might want verification from some others.

Al

[QUOTE=Cocephus]Wouldn`t that hinder the oil penetrating into the wood[/QUOTE]

Yes, exactly--and that's a good thing! On guitars, we want a SURFACE finish only. Anything that penetrates will damp the wood's vibrations. Also any oil (e.g. Danish, tung, linseed, etc.) that isn't polymerized won't dry hard and won't provide much protection against moisture or solvents. Polymerization is a heating process in an oxygen-free environment, and it changes the chemical makeup of the oil--it will then dry hard, provide protection, and build to a shine. Oil varnishes use a similar heating process and will dry hard, but don't confuse it with varnish WITH oil added--it's not the same! Also, "boiled" linseed oil isn't--boiled, that is. It just has additives that help it to dry faster, but it still drys to the same kind of finish as raw linseed.

You've probably read here recently that some folks are using Behlen's Rockhard varnish on guitars. It's a true varnish, and has the hardness qualities we need. Also, though the manufacturer claims it isn't a varnish, Tru-Oil contains polymerized linseed oil with propriatary additives, and is also used on guitars with reported good results.

Hi Coe
What the others have said about penetration is right, Walnut especially will soak up oil and this is not good for the acoustics. I like to use a seal coat of Shellac then apply Danish Oil over it, I have never found a Tung Oil that I liked.

There is a lot of mis labeling of oils, you can get pure oils, but most oils, are actually blends of oil and Varnish, which suit our purposes better than pure oils.

A pure oil is a truely penertrative finish which creates its seal under the surface of the wood, great for things like counter tops.

The Oil Varnish Blend build to a degree on the Surface.

I Like the products by Rustins especially their Danish Oil, I also Like Tru Oil.

A little Tip for Oils decant the amount you want to use into a small container and work with in from there, as I find if you work straight from the can you waste a lot as it deterioates when you have the cap off

I see what you mean, guys. I did some testing/practice on some off cuts, and found that the tung oil does penetrate too far and also makes the pores stand out too much.
As far as the french polishing goes, it reminds me of putting a good spit shine on my jump boots when I was in good `ol Ft. Benning, GA. Gotta pay attention to what you`re doing, though. What I really like is the ease in which you can repair mistakes and touch up.

_________________
Give me 50 cents worth of regular.
Check my oil too, if you don`t mind,,,

[QUOTE=Cocephus] As far as the french polishing goes, it reminds me of putting a good spit shine on my jump boots when I was in good `ol Ft. Benning, GA. [/QUOTE]

Hey, Coe...did you use the "flaming polish" technique? Somehow, melted shoe polish shines up much better when you also dip your cloth in water, or add spit. 'Course, I managed to start a small fire in my barrack, but helpful fellow-trainees put it out before any real damage was done! Apparently the news never made it up the chain of command, either. Whew!    As for FP, you'd have to substitute pure grain alcohol for the spit...oh, wait--I knew some guys in the service who could have used spit!

Just to add a little...

Natural oils, like linseed and tung, are mixtures of oils with different molecular weights, and harden by an oxydation/polymerization reaction. The lighter molecular weight components of linseed oil can go right through a 1mm thick violin rib in a year or less. Martin Schleske, in an article that published in the Catgut Journal back in '98, stated that all oils have fairly high damping factors. This might not be a bad thing on a fiddle, but you _don't_ want that on a guitar, especially the top. Also, because they penetrate so deeply, oils tend not to form a good protective film, unless you build tem up. Weight is the other thing you don't want on a guitar top....

Many resins have fairly low damping factors, and, since they naturally tend not to penetrate and to form a good film, they usually make better finishes for guitars. Shellac and nitro both have _lower_ damping than cross grain strips of wood, according to Schleske, so a thin film of either might do more good than harm, assuming the weight is kept down.

What I think of as 'true' varnishes are made by cooking an oil and resin togethe to form a co-polymer. You get some of the advantages and drawbacks of each. Varnishes tend to have a higher damping factor than straight resins, but gain a lot of toughness and flexibility from the oil content. If you use a 'rubbing' or 'short oil' varnish the damping should not be too high. Stay away from 'spar' or 'long oil varnishes: we don't need that kind of flexibility, and the extra oil content is a problem.     

Carlton, Yeah, I used to put some Old Spice after shave on top of my polish when I was putting on the base coat on a new or badly damaged pair of boots and "flash it off" to make it soak into the leather better. That way it wouldn`t flake off on you. For some silly reason my feet never reeked like alot of the others` did!
Alan, I`ve been searching all over this little county in Indiana for a local supplier of FP supplies and they all look at me if I were from Mars. I think the Amish population might have something to do with that, but it`s beside the point. Have you heard of a product made by Minwax that`s supposed to be the "best clear finish made yet (tougher, guaranteed not to yellow or shrink). Maybe it`s a polymer. I can`t seem to recall right off.

_________________
Give me 50 cents worth of regular.
Check my oil too, if you don`t mind,,,

[QUOTE=Cocephus] it reminds me of putting a good spit shine on my jump boots when I was in good `ol Ft. Benning, GA. [/QUOTE]

Co, I have fond memories of coming to Fort Benning in the early 70s for a British team match against the US international shooting team (we won!), who at the time were all training as full time members of the US Army Advanced Marksmanship Unit, based at Fort Benning. We flew from Mildenhall air base in the UK on a USAAF plane and never once went through passport control or customs, it was as if we never left the UK. Bought a lot of US taxpayer subsidised kit from the base PX!

Colin

_________________
I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

Colin, In a strange way, I do rather miss good `ol Harmony Church which is an area of Ft. Benning for infantry basic training. I was a drill instructor in that area for awhile, `til I found that it was too much like babysitting a bunch of adolescents.
These days, I get to thinking about those tall Georgia Pines...
AT EASE! DRIVE ON! Carry on like the animal you really are!
Coe

_________________
Give me 50 cents worth of regular.
Check my oil too, if you don`t mind,,,

All this talk of boot shining is stirring up memories for me. In the US Navy we sometimes did what we called a "burn shine". Open a can of Lincoln brand black shoe polish and set it ablaze with a match until the top is melted. Then with a piece of cotten t-shirt tightly wound around 2 fingers, dip into the hot melted shoe polish, and quickly rub into the shoe/boot leather in a circluar motion. Follow this with another piece of cotton shirt dipped into ice water. A mirror shine in minutes. It's a little bit like FP.

CrowDuck

_________________
Chris Nielsen
Soquel, CA.

Exactly the way I used to do it.

_________________
Give me 50 cents worth of regular.
Check my oil too, if you don`t mind,,,