Tru-oil

[whoofnagle]

Well it has been a few weeks since I finished my Koa and Ash guitar with tru-oil. I think the look is exactly what I wanted, but man it has not hardened worth a darn on the Koa. It is dry to the touch, but it scratches so easily. I am about to restrip the top and redo the finish. Like others, I used many 50/50 coats cut with Naptha.

Can I spray a coat of something over the oil to better protect the finish?

I am still new to doing finishes.

Thanks,

Bill

[erikbojerik]

I've not actually done this, but I've read many places that you can scuff sand with 600 and shoot polyurethane over top of Tru Oil.

I've also read that this either does or does not work with nitro.

[whoofnagle]

I've not actually done this, but I've read many places that you can scuff sand with 600 and shoot polyurethane over top of Tru Oil.

I've also read that this either does or does not work with nitro.

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I just picked up a can of minwax spray poly. I will give it a shot on some scrap wood tomorrow.

[unclej]

you'll want to make sure that you get all of the tru-oil off of the koa. if it's not completely cured now shooting poly over it will keep it from ever curing properly and could cause problems down the road.

lightly scuff the back of the guitar then take all of it off of the front. read the directions on the tru-oil bottle and see what they suggest you use for clean up..i.e. naptha, paint thinner, etc. wipe the front down several times with whatever material you choose and let it dry over night. you'll want to shoot both the front and the back with your poly or you're going to have different looks and a difficult time blending the two sides so that it looks good.

good luck.

[whoofnagle]

you'll want to make sure that you get all of the tru-oil off of the koa. if it's not completely cured now shooting poly over it will keep it from ever curing properly and could cause problems down the road.

I will certainly do the whole guitar once I strip and reapply the tru-oil to the top. I guess my main concern is whether or not poly is a suitable to apply over the oil (based on the few responses - it seems okay). Again, I like the look of the oil, but I would also like a little harder finish.

Bill

[unclej]

i don't mean this as a smart alec reply but if the tru-oil didn't harden on the top the first time it's not likely to harden the second time. and spraying poly over it isn't going to give you an oil finish look..it's going to look like poly.

i'm not that familiar with tru-oil but someone might be able to tell you whether or not you can add a hardener to it before you apply it. if not and you really think the wood has something to do with why it didn't harden then i'd go with a different type of oil finish or i'd go straight poly.

just my opinion.

[VanKirk]

I had good luck experimenting on scrap with poly over Danish oil.

It gave me that nice glow that tru-oil did on my other scraps but is wayyy harder.

I think it even popped the grain just a bit better than the tru-oil too.

[erikbojerik]

It really depends on what you mean by "hard".

If you apply Tru Oil too thick, it will never harden enough to pass the fingernail test (i.e. you can dent the finish with your fingernail).

If you apply it thin enough, especially cut 50/50 with naptha, it will dry hard enough that you can't dent it with the fingernail. However, it is still not as "hard" as cured polyurethane (and never will be).

Then there's poly-hard, which is about as hard as you can get short of finishing with epoxy.

My point is....you may not need to strip the Tru Oil from the Koa at all. If it passes the fingernail test, then just scuff with 600 and go with the poly. If not, then strip and re-apply one or two 50/50 coats, let cure fully, then scuff & shoot the poly.

Finally...the rattle-can poly will go on very thin. You'll have to be very careful to not sand through your previous layers when you buff out. I've had good luck getting it to lay thicker by laying the body down flat, standing off the table with wood blocks stuck into the pickup routs (front) and tremolo rout (back).

[whoofnagle]

Thanks for the tips.

UncleJ - I did not take offense. Maybe I did apply it too thick on the top, because it still scuffs with the fingernail test. The reason I would put a few coats of tru-oil back on prior to adding the poly is to make sure the finish looks uniform on the whole body. The back seems to be okay. Yes, I could strip the whole thing and just shoot poly, but that seems like it is a bit much.

Again, I am learning here so that down the road I do not make the same mistake again.

Bill

[Doc]

There are a lot of funiture makers who hate the finshing part who use a mixture of oil, polyurethane and solvent. The percentages are done by trial and error.

Oil finish is never going to harden up like a film finish. It is not lacquer or polyurethane. It isn't intended to be.

It gives a nice flat to semi flat relatively protective coating tha is subject to scratching and water spotting, but is easy to apply and easy to repair. It will darken in time and is the most water permeable of any furniture type wood finish.

If you want to have the look of polyurethane there is no reason that you can't go directly over the oil. Try mixing a little of the oil with some poly and try it on a test board. If that hardens you have absolutely nothing to worry about.

I don't know diddly about Tru-oil brand other than what I've seen here. Has anyone got a link to a site that sells or makes it?

[marksound]

Birchwood Casey

I was in the neighborhood.

[jnewman]

The actual brand is Birchwood Casey (which makes a variety of firearms/shooting accessories and products), while the product is Tru-Oil, marketed (and used for a long time) as a gunstock finish.

Here's the site of the finish itself: http://www.birchwoodcasey.com/sport/index.html

Interestingly, they seem to have an aerosol version - I've never seen that before.

It seems to be a LOT cheaper from their website than from Walmart or your friendly neighborhood gun store.

They sell it in 3oz bottles (all you'll EVER find in Walmart or gun stores), 8oz bottles... and gallon bottles. I bet a lot of people here wish they'd known they didn't have to use a bunch of tiny bottles of the stuff . Plus, a gallon's $50 - 3oz bottles are not quite $6. You'd save something like 75%.

Edited October 10, 2005 by jnewman

[Doc]

Thanks for the directions guys. This appears to be a simple product that is charging you for coonvenience and a brand name.

All this stuff is is boiled linseed oil and solvent with "other oils" added. My guess is that the other oils are a little tung oil. The solvent is probably mineral spirits.

You can mix up your own for a lot less, and it is truly not rocket science.

A quart of boiled linseed oil should cost about $10. I've got a quart of Behr tung oil on the desk here that is old as the hills and cost me $12.

Fine Woodworking has run scads of articles on this typr of finishing. Check their website at Taunton press and look for back issues.

When I oil finish I use straight Tung oil. I get great results and frequently wind up top coating with nitro for durability or gloss, with few or no problems.

[jnewman]

Actually, tru-oil is a pretty hard-drying (if you do it right) polymerized other-stuff-added business - you can actually build up a gloss film with it if you try. It's not just linseed oil, and having used a few polymerized oil or polymerized oil/phenolic resin varnishes lately, tru-oil does come out differently.

[whoofnagle]

Actually, tru-oil is a pretty hard-drying (if you do it right) polymerized other-stuff-added business - you can actually build up a gloss film with it if you try. It's not just linseed oil, and having used a few polymerized oil or polymerized oil/phenolic resin varnishes lately, tru-oil does come out differently.

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What defines doing it right? It sounds as if you have had some success? Based on several posts above - I feel that I might have been doing it too thick.

Bill

[jnewman]

I haven't personally used Tru-oil, but I've seen some stuff finished with it that looks really good. I think the general concensus is to thin it with naphtha and put the coats on as thin as they'll go on, and give it a little while between coats.

[erikbojerik]

What defines doing it right?  It sounds as if you have had some success?  Based on several posts above - I feel that I might have been doing it too thick.

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You almost can't put it on too thin. I use a 2"x2" square of T-shirt with a cotton ball tied up inside; saturate it with Tru Oil, gently squeeze out the excess, then cover with a thin layer. If you hang the guitar while finishing, you should apply it thin enough that you get no runs whatsoever...not even close. If you have even the slightest run, you're putting it on too thick.

It cures by oxidation, which means the air needs to get to it. If it goes on too thick, or even too many layers too quickly, a skin will build up that prevents air from getting in, and you'll end up with gum.

[whoofnagle]

What defines doing it right?  It sounds as if you have had some success?  Based on several posts above - I feel that I might have been doing it too thick.

←

You almost can't put it on too thin. I use a 2"x2" square of T-shirt with a cotton ball tied up inside; saturate it with Tru Oil, gently squeeze out the excess, then cover with a thin layer. If you hang the guitar while finishing, you should apply it thin enough that you get no runs whatsoever...not even close. If you have even the slightest run, you're putting it on too thick.

It cures by oxidation, which means the air needs to get to it. If it goes on too thick, or even too many layers too quickly, a skin will build up that prevents air from getting in, and you'll end up with gum.

←

Do you have a recommended finishing schedule?

Bill

[erikbojerik]

Here's what I've done on my bass proj:

FIRST...I made sure I had the highest quality hand-sand job possible, working down from 320-400-600-1000 (wiping with naptha between). Then:

4 coats full strength 30 minutes apart, first one pretty thick as the raw wood drinks it right up and you want deep penetration into the grain (but you've already got this). Dry overnight.

Scuff sand w/ 1000 grit (Abralon pad dry) until there are absolutely NO shiny spots; you want everything matte. Wipe down with naptha.

One thin coat full-strength first thing in the morning, one in the evening, with 1000-grit scuff and naptha wipe in between each coat. I did this every day for two weeks, grain filled in nicely. Anywhere in here, you can bring in the 50/50 TO-naptha mixture, it will cure quicker (2-3 hours) and allow you to do 3-4 coats per day, but they are even thinner than the full-strength coats.

One last 50/50 coat after final 1000 grit scuff; the 50/50 coats cure to a nice gloss, I did no buffing afterward. The trick on the last coat is to get a good gloss with no tiny bubbles; if I find some, I just let it cure, scuff again and re-coat...keep going until I'm happy with the last one. I never did buff.

Scrape off and sand down any and all runs that appear, as they will never cure. But if you're going thin enough, you won't get any. If you sand through previous layers you'll get rings, or so-called "witness lines" that will never buff out; you'll need to cover them with another 50/50 layer, then they'll disappear. Probably they'll disappear with poly over top as well.

I may end up using poly over my TO job, I'll have to see how it wears.

[VanKirk]

That's sounds close to the process I used but instead of the Naptha-thinned coats I used the aerosol version which is already thinned.

If you were going to use poly over tru-oil though I would strongly suggest trying 2 coats of Danish oil then go right to the poly instead to save alot of time and sanding.

Try it on scrap and compare your results with the tru-oil.

IMO, I really think the Danish oil looked better than the tru-oil as far as grain popping went and you get the same slightly amber glow with either one.

2 coats Danish oil, shellac as grain-filler if needed then right to the poly would be my personal choice.

[whoofnagle]

Thanks for all of the suggestions. I have a few test scraps going now. Once i figure out what works best for me I will think about stripping the guitar, but until then I can live with the scratches - I love the way the guitar saounds.

Again thanks for the help,

Bill

[javacody]

From what I've read and experienced, you want to wipe off any oil finish after about 15 minutes. Wipe on, let sit for 15 minutes, wipe off. Let it dry overnight, repeat. Now tru-oil may cure faster, but I'm pretty sure you still want to wipe it off after 15 minutes, otherwise, its going to go on way too thick and not dry properly.

Before I started using oil finishes on guitars, I researched what gun owners do to their stocks, and the information is similar to, if not the same as what I presented above. Do the research anyway.

Here's some food for thought:

http://www.findarticles.com/p/articles/mi_...002/ai_n8892269

Another good resource is about doing a hand rubbed poly finish:

http://www.frettech.com/info.html

Another great set of articles on sealing, pore-filling, and finishing a gun stock with oil based products:

http://riflestocks.tripod.com/seal.html