#1
I was putting on a Tru-Oil finish on a guitar (I've had troubles with spray cans and can't afford a proper mechanism yet for a real spray setup), however I've noticed three things going on that I'm not sure exactly what the cause is and before I start experimenting I thought I'd ask for opinions before ruining the guitar(more than I already


Here's a link to the photobucket slideshow to view the 4 images.
http://s347.photobucket.com/user/ShallonDark/slideshow/

The areas I have questions are
On the back I had huge globs form, when I checked them on saturday they were still gummy. Is it better to 1. let these dry, then sand them down, and then add more tru-oil, 2. Let them dry, add the rest of my layers, and then sand them at the end before polishing. 3. Bust them out now while still liquid and gap fill the holes.

All over the guitar are little bumps, I'm not sure if these are from uneven coats, the wood underneath not being sanded well, or if they are from dust and particles that have either landed on the guitar or attached to the rag. Best to sand them out and and then continue coating or?

On some of the edges, there appears to be rough porus areas, they feel like the natural wood, and because of the curvature of the body type, I am assuming they just need more coats to layer, however, I guess I'm worried these "porus" areas are going to show underneath the coat. I assume they needed more sanding before starting the tru-oil process?

Also, finally I didn't use any type of grain filler or sealer before hand, as I was worried it would not take the stain or it would take stain differently than the natural wood, was this a mistake? How do I make sure fillers don't look wierd when using a stain? (On painted guitars I use it, because the spray paint creates an even coverage and I'm not worried about the stain color of the wood).

Thanks for the assistance! I'm trying to learn.
#2
Preparation should be a sanding to at least 200 grit so that you have a smooth surface to work with. I usually use a sanding sealer to eliminate uneven uptake of stains or oil finish. 

Tru-Oil is essentially a boiled linseed oil finish. When I've applied it, I've thinned the first layers quite a bit. Apply sparingly, leave it sit for about 1/2 hour and then remove any excess oil with a rag (some folks rub pretty hard at this stage). Let it dry at least 24 hours (longer is better) and then apply another thinned layer, leaving it sit for about 1/2 hour and then rubbing the excess off, and allowing it to fully dry (again, at least 24 hours or more).  I work up to undiluted layers, but I'm really careful to apply in as thin a coat as possible and to NOT to allow excess to sit on the wood after 1/2 hour. You can end up with a sticky mess that may never dry. 

I sand between layers with 0000 steel wool, being careful to run over the surface with a tack cloth before I begin applying another layer. 
#3
It looks like the bumps are lint and dust.  The rough grain is because you didn't seal the wood before applying the oil.  It also looks like you have been applying the oil too thick to compensate for the fact that you didn't seal the grain.  You need to apply the layers as thin as possible using lint free cloths.  If you want a smooth finish you need to fill the grain.  I use shellac and pumice for this.  A lot of people like to use system 3 epoxy as a grain filler and I use it for lacquer finishes but for an oil finish I like to use shellac and pumice as the filler.  If you opt to use shellac you need to mix your own, don't use premixed because the premixed stuff has preservatives that causes the shellac to never fully harden.  Filling the grain with shellac and pumice is part of the prepwork for a good french polish so google french polishing to find tutorials on how to fill the grain.

After the grain has been filled you can start to apply the oil but I have found that the directions on the bottle don't work well for guitars.  True oil is a gun stock finish so the directions are meant for people that want to put it on a gun.  I have found that I get the best results when Iwipe a small amount over the whole guitar then get a new rag and wipe it dry.  Failing to wipe it dry slows down curing dramatically and it causes more dust to get caught up in the finish.  I don't give the oil time to soak into the wood because I find that I get a smoother finish with less lint and dust if the finish is wiped off immediately.  After each coat you should let it set for about 24hrs then lightly sand it with 200 grit paper.  Sanding between coats isn't to smooth the finish it is to give the next coat a better surface to adhere to.   Only after you get about 8-10 coats of oil on the guitar will you want to let the guitar set for about 2 weeks (give or take depending on how many coats you used) and then start sanding to smooth and level the finish.  This should be done with 400 grit paper.  If you accidentally sand back to wood then you will have to apply a couple more coats of finish but if everything seems good after leveling the finish you need to decide if you want a glossy finish or a matt finish.  If you want a glossy finish apply 1 more coat as thin as possible and wipe it off moving with the grain.  This will add a gloss and shouldn't need any more sanding.  If you want a matt finish then instead of applying another coat simply bump the sandpaper grit up to 800 for 1 more light sanding.
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#4
It looks like you've put way too much on (thick coats, or whatever). You really need to apply the thinnest layer and then wipe off, as dspellman said. You can buy a Tru-Oil grain filler, which builds a little better than the regular finish. Also, consider sanding with 400 grit for the first few coats, working perpendicular to the grain; that should help to fill any open pores.

Pro tip: If you're getting gummy patches, apply another thin layer of Tru-Oil and leave for a few minutes before wiping off. Tru-Oil contains white spirit to melt the finish and help to blend layers.
#5
Quote by CorduroyEW
It looks like the bumps are lint and dust.  The rough grain is because you didn't seal the wood before applying the oil.  It also looks like you have been applying the oil too thick to compensate for the fact that you didn't seal the grain.  You need to apply the layers as thin as possible using lint free cloths.  If you want a smooth finish you need to fill the grain.  I use shellac and pumice for this.  A lot of people like to use system 3 epoxy as a grain filler and I use it for lacquer finishes but for an oil finish I like to use shellac and pumice as the filler.  If you opt to use shellac you need to mix your own, don't use premixed because the premixed stuff has preservatives that causes the shellac to never fully harden.  Filling the grain with shellac and pumice is part of the prepwork for a good french polish so google french polishing to find tutorials on how to fill the grain.

After the grain has been filled you can start to apply the oil but I have found that the directions on the bottle don't work well for guitars.  True oil is a gun stock finish so the directions are meant for people that want to put it on a gun.  I have found that I get the best results when Iwipe a small amount over the whole guitar then get a new rag and wipe it dry.  Failing to wipe it dry slows down curing dramatically and it causes more dust to get caught up in the finish.  I don't give the oil time to soak into the wood because I find that I get a smoother finish with less lint and dust if the finish is wiped off immediately.  After each coat you should let it set for about 24hrs then lightly sand it with 200 grit paper.  Sanding between coats isn't to smooth the finish it is to give the next coat a better surface to adhere to.   Only after you get about 8-10 coats of oil on the guitar will you want to let the guitar set for about 2 weeks (give or take depending on how many coats you used) and then start sanding to smooth and level the finish.  This should be done with 400 grit paper.  If you accidentally sand back to wood then you will have to apply a couple more coats of finish but if everything seems good after leveling the finish you need to decide if you want a glossy finish or a matt finish.  If you want a glossy finish apply 1 more coat as thin as possible and wipe it off moving with the grain.  This will add a gloss and shouldn't need any more sanding.  If you want a matt finish then instead of applying another coat simply bump the sandpaper grit up to 800 for 1 more light sanding.

That works. 
#6
From what I see in the pictures you are laying on the oil way too thick, 4 or 5 light coats is better than one heavy coat. Oil finishes need to be applied very sparingly and rubbed in. Then lightly buffed with a gray 3m scratch pad  before applying then next coat. You should never put on so much that it can run or pool up. A good hand rubbed oil finish should take 6-10 coats for a nice satin finish and up to 30-60 coats for a deep gloss.

If it were my project I would strip what is on it and start over. Also cut your tru-oil with mineral spirits or japan drier, a thinner oil penetrates better and is easier to work in and put on thin.

Here are some pics of a 1952 Remington 40X in a Freeland Style Stock I refinished for a customer, It took 3 months and 50+ coats of hand rubbed oil.

This is what it looked like before I started, the rifle was from the estate of a world class target shooter. He rasped the wood to fit him, he did not care about looks he cared about performance. The whole stock looked pretty rough.


After sanding to 400 grit and matching the vintage Remington Red color the oil can slowly and painstakingly laid on. A good oil finish is a much more complex and labor intensive way to finish wood than just spraying on a lacquer or poly.



This is after about 20 coats of hand rubbed oil, it is a gloss but not a deep rich gloss.


After 50 coats the project is complete after a final polish with compound and a buff with carnuba wax.
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Last edited by Smith357 at Apr 23, 2017,