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I’ve used danish oil on necks and electric solid bodies, but no experience with Tru Oil. Something that I use quite often on necks and all types of wood projects is a mix of linseed oil, mineral spirits, and oil based poly all in equal parts and this works very well for wiping.

I’ve have always avoided using danish or any kind of oil finish on acoustic tops out of fear it would penetrate the wood and alter things in a negative way. Recently I have seen fellows claiming they are using tru oil on acoustic tops and like the results. Have I been mistaken in believing that oil based finishes could negatively impact the instrument acoustic properties when applied to the sound board, is Tru Oil unique in some way or am I missing something? I suppose with a good sealer coat of something prior to an oil based application would work but I don’t know never tried it on a top.

Oil finishes do tend to damp the sound if they soak into the wood. A light coat of a drying oil can be used to enhance the the color and "pop" the grain of some woods.
That being said, Tru-oil is not a true oil finish. It is a "Var- oil" . Essentially a wipe on varnish. The initial coat will soak in a little bit and polymerize and seal the wood. Subsequent coats will build on the surface. It is a "thin" material so many coats are used to build a finish, similar to French polish.
Here is some additional reading for your edification:
https://askinglot.com/what-is-tru-oil-made-of
http://www.mikeouds.com/messageboard/vi ... ?tid=12156

Ken Parker coats with epoxy (west I think) then tru oil. he has some videos on it

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Mike McNerney

Tru-oil is great for necks. Especially electric ones.

mike

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Mike Collins

I've gotten conflicting reports as to the nature of Tru-Oil. Some say that it is a mix of varnish and oil, while others claim it's linseed oil that has been heated in the absence of air to polymerize it. I rather incline toward the latter explanation at present.

Martin Schleske did a study, reported in the 'Journal' of the Catgut Acoustical Society in Nov. of '98, comparing the effects of various finishes, including drying oils and oil-resin varnishes. He found that straight linseed oil on wood added mass and damping, but did not provide a good water proof film over the long term. Linseed oil has fractions of different molecular weight, and the lightest ones can penetrate deeply into the wood before they harden, so it tends to add a lot more mass than something that forms a film on the surface. All of the finishes that had il in them, even the cooked oil-resin varnishes, added damping, more or less in proportion to the fraction of oil in their makeup; so 'long oil' or 'spar' varnishes added more damping than 'short oil' , 'rubbing' varnishes.

I'm pretty sure it was Mayer in his 'Artist's Handbook of Materials and Methods' who pointed out that linseed oil never really stops reacting with oxygen, shrinking and getting harder as it does so. Over time a coating of oil can actually cause canvas to 'rot', tearing it up as it shrinks. This necessitates the common restoration practice of 're-lining' a painting: stripping the old canvas off the back of the paint layer and putting a new canvas on.

I'll note that none of this directly addresses the long-term effects of Tru-oil. If I was more sure of what the stuff is I'd be more sure of that. If, as I suspect, it's a polymerized linseed oil, then it would have few, if any, low molecular weight fractions, and should not penetrate deeply. That would limit the added mass and damping. It's possible that Tru-oil does produce a water proof (rather than merely water repellant) film. I note that, as a gun stock finish, it's meant to be re-applied periodically, which would renew it's water repelling ability. I have used Tru-oil as a neck finish when so requested, but I avoid putting it on tops. I suppose the whole thing could be settled if we just asked Sherwood-Casey what it is...

On tops I seal first with a couple of coats of Shellac then Tru Oil on top. Works well for me

I know this thread is old, but it seems to be the best place for this question:

Now that Tru-Oil is increasingly difficult to get here in California (LMII no longer carries it, and most of the gun stores can't get fresh stuff anymore), what would be the next best thing for guitar necks? I've been using Tru-Oil exclusively for necks, but my current stock is over three years old and I don't really trust it now.

I've ordered it on Amazon....no problem in delivery to CA then. Looks like only 3oz and 32oz (no 8oz) in stock now. https://www.amazon.com/Birchwood-Casey- ... =8-39&th=1

I used it on one guitar once and like Bob I seal with shellac so even if it does penetrate wood it will not if sealed. It's so easy to use and the results are so good I don't know why I don't use more of it. I have seen others work using Tru-Oil too and the results were fantastic. That would be a shame if the company stops making it or reformulates it for what ever reasons.

Strange, because the last bottle I got at the gun shop here was labeled "Not for Sale in California.

I'll have to look into it further.

I've finished one whole guitar and one mandolin with it, and was quite happy with the results. But I find it most useful for parts that get a lot of handling, like necks.

Hey John,
Order it , if it's not delivered, Amazon will refund it.
Use the link ^^^ to support OLF.

It turns out that I've found a partially used bottle and an unopened bottle in my supply cabinet. I've tested the open stuff and still found it good, so I think I'm set for the next half-dozen necks. (I use the Behlen/Mohawk rattle-can nitrocellulose on the bodies.)

I have used tru-oil many times and have been very pleased with the results . It is very forgiving and easy to repair .

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