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I don't use the stuff myself but I did come across this process -- I do believe that those thinking about using Tru-oil should rest assured that their guitars will be just fine and according to some reviews will have a superior finish "appearance and acoustics."

This is how Jonathan Kinkeade does it:

While not as protective as polyurethane, polyester or nitrocellulose, its visual and tonal advantages outweigh these shortcomings. The key is in the way the wood is prepared prior to application. After the normal progression from scraper to extremely fine (1200 grade) wet and dry paper, Kinkead moves on to micro-mesh paper invented for polishing Perspex in the aerospace industry – which goes up to an incredible 12,000 grade. This produces a mirror-polished surface on the bare wood, normally unnecessary for other finishes. Then several applications of a substance called Tru Oil, normally used in the gun industry, is rubbed in over several days. Finally, after a week of drying, the guitar is buffed to a shine.

I did my second guitar - redwood top, eir b&s - with tru oil, and my sister in law has played it almost every day for a year and a half and it still looks great.
DaveB

The major appeal to me with TruOil is that I can do it in my house. I use nitro now and I have to do it outside in my detached garage. That means I have to wait for the weather to be nice enough to apply the stuff.
I finally saw a poorly Tru_oil-ed guitar in person recently, and even though it was poorly executed, it still gave the wood a nice glow.

Since my first go around with tru oil I've been experimenting with it on scrap and getting pretty good with it. Surface prep really is key.

Sanding up to 12,000 does seem incredible. Does that negate the need to use some type of sealer on the wood before applying the oil?

mjmeehan wrote:Since my first go around with tru oil I've been experimenting with it on scrap and getting pretty good with it. Surface prep really is key.

Sanding up to 12,000 does seem incredible. Does that negate the need to use some type of sealer on the wood before applying the oil?

There is no need to use a sealer with TO. It will make it's own "Sealer" and is often sanded in a slurry to create a pore filler as well.

Just a word to remind everyone of the wide misconception that Tru-oil is NOT an "OIL" finish...like Tung Oil...it is a hard, dry, sand-able, permanent finish that can be polished as well as any other hard finish.

It can be applied in any number of ways with excellent results...

It can also be sprayed successfully, if thinned 2/1 with mineral spirits and applied in coats of 3, allowed to dry over night, sanded with 320, wiped clean with a micro fiber cloth lightly dampened with naphtha to remove any dust and shot again...usually 12 coats are ample in this manner...then polished up to 12K as you wish.

Ray (:0)>}

I believe The label says:

"Tru-Oil® is a polymerized linseed oil with other natural oils added. "

So its a kind of varnish

Since first reading this thread I've been wanting to try the process out. I have and I can show the results. The pic below is of two pieces of Ash, no pore filler. The one on the left was sanded to 400 grit and has a thin coat of shellac covered with 6 coats of Tru Oil. The one on the right is sanded through the grits to 12,000- no finish. I was impressed with the result.
Next I can see how it takes the tru oil and compares to the initial application.

My first build is coming up to it's second birthday and the tru oil finish is standing up well to all I am throwing at it. For ease of use and non toxicity it is great stuff. It goes off if it left in a bottle which is partly used, I read about a guy who puts marbles in the bottle to bring the level of the liquid up so that most of the air space is removed and this helps it last longer. I am going to give that a try unless anyone has any other ideas.

WOW!! mj, that wood you polished up to 12,000 looks like it has been lacquered!! Thats pretty amazing! Should take a nice coat of TO now!

That's the way Kinkade does it, though I am not sure if he pore fills first or not. Up to 12000 and then tru-oil.
I'm real interested to see how this turns out.
DaveB