Tru-Oil help

Need a little consulting on a new build with a Tru-Oil finish. I've read how in countless threads how it is pretty foolproof which has me feeling a little :oops:.

Things were looking very nice through about 10 coats. I had lightly sanded after every couple of coats and had wet sanded with 400 and mineral spirits at 10 hoping to finish with one last coat. However, that last coat had streaking and flat spots, I sanded it back again and reapplied but the same result. I let it sit a week and tried again - same result (breaking the Gomer Pyle rule - fool me once, shame on you, fool me twice, shame on me.) I also notice the hardness was less than what I expected and would mark/dent rather easily with a fingernail or pick.

To get to this point took me about 4 weeks. Coats were very thin. I was using a 3 oz. bottle with a pin hole in the foil on the top although I did leave the cap off overnight a couple nights. I

It started after I wet sanded. Was it ok to use mineral spirits for that? Or is it possible the Tru-Oil became contaminated with moisture?

I no expert on tru oil but isn't mineral spirits is a thinner for oil based paints vanish and such.May be that has something to do with your problem

You shouldn't try to sand or polish tru oil until it has had about 2 weeks to dry. Before then, its too soft to buff.

Hard to tell what you are calling flat spots, but I suspect you are actually sanding through to the wood or sealer.

Tru Oil is a nice finish, but it needs to be applied in thin coats. Needs ample time to dry between coats, and I like to knock down bumpies and such between coats with steel wool. After about 12-15 coats, I would it dry two full weeks before trying to wet sand and buff.

You shouldn't try to sand or polish tru oil until it has had about 2 weeks to dry. Before then, its too soft to buff.

Hard to tell what you are calling flat spots, but I suspect you are actually sanding through to the wood or sealer.

Tru Oil is a nice finish, but it needs to be applied in thin coats. Needs ample time to dry between coats, and I like to knock down bumpies and such between coats with steel wool. After about 12-15 coats, I would it dry two full weeks before trying to wet sand and buff.

I was hoping you would jump in on this, Colt. I've learned alot from your posts in other threads. By flat spot I was referring to dull surface gloss compared to some of shiny streaky patches. Very inconsistent overall.

I assume I need to sand back past any shiny streaks to get a consistent surface to work from and then build back up. I bought a new bottle to work with just in case there was some moisture contamination.

Can you comment of the hardness of the fully cured Tru-Oil finish? We did not use a pick guard. Should we expect to see visible pick marks?

I was hoping you would jump in on this, Colt. I've learned alot from your posts in other threads. By flat spot I was referring to dull surface gloss compared to some of shiny streaky patches. Very inconsistent overall.

I assume I need to sand back past any shiny streaks to get a consistent surface to work from and then build back up. I bought a new bottle to work with just in case there was some moisture contamination.

Can you comment of the hardness of the fully cured Tru-Oil finish? We did not use a pick guard. Should we expect to see visible pick marks?

Tru Oil is a firearm finish, and when applied properly is a tougher finish than lacquer.

My experience with Tru Oil is mostly with firearm refinishing. Firearm guys are not into relicing, and frequently expose their finish to much harsher elements than a guitar.

Tru oil is almost as finicky as lacquer. Depending on the thickness of your coats and the temp./humidity, drying time between coats can far exceed the directions on the bottle. I believe the bottle says 2 hours, but I frequently have to let the oil set for 12-24 hours before its hard enough to buff with steel wool and apply a subsequent coat. I do not use Tru Oil for a high gloss finish. Lacquer is far easier to work with for a high gloss finish. However, Tru Oil looks great as a semi gloss or satin in my opinion.

I finally got a tru oil finish I was happy with but it took over a month. Would have taken me less time but it started to get too gummy, even though I exposed the open bottle to air as little as possible. I ended up getting a second bottle and was then able to get the finish I wanted with a few more thin coats. Regarding the hardness, it's probably too soon to tell, but it seems to be holding up a few months later. But I also went with tru oil not minding if the finish ultimately gets some scuffs and dings. If I wanted a long-lived mirror finish, I would have just poly'd it.

I finally got a tru oil finish I was happy with but it took over a month. Would have taken me less time but it started to get too gummy, even though I exposed the open bottle to air as little as possible. I ended up getting a second bottle and was then able to get the finish I wanted with a few more thin coats. Regarding the hardness, it's probably too soon to tell, but it seems to be holding up a few months later. But I also went with tru oil not minding if the finish ultimately gets some scuffs and dings. If I wanted a long-lived mirror finish, I would have just poly'd it.

There is a big difference between polyurethane you buy at the hardware store for wood working projects and urethane used by automotive and big name guitar companies.

... wet sanded with 400 and mineral spirits at 10 hoping to finish with one last coat. However, that last coat had streaking and flat spots, ...
400 grit is way too aggressive. My best guess is that you got down into wood in spots and that is why its showing different levels of shine.
Wet sanding with a little bit of mineral spirits is fine once the Tru Oil has cured at least overnight, but go with some 1000 grit or higher. I find that 1000 cuts fast enough on the new and fragile film to get results, but not so aggressive that you blow through in a couple strokes.

400 grit is way too aggressive. My best guess is that you got down into wood in spots and that is why its showing different levels of shine.
Wet sanding with a little bit of mineral spirits is fine once the Tru Oil has cured at least overnight, but go with some 1000 grit or higher. I find that 1000 cuts fast enough on the new and fragile film to get results, but not so aggressive that you blow through in a couple strokes.

^^^This guy gets amazing results with Tru Oil.

400 grit is way too aggressive. My best guess is that you got down into wood in spots and that is why its showing different levels of shine.Wet sanding with a little bit of mineral spirits is fine once the Tru Oil has cured at least overnight, but go with some 1000 grit or higher. I find that 1000 cuts fast enough on the new and fragile film to get results, but not so aggressive that you blow through in a couple strokes.


Emphasis added by me.

I've had this same problem. Where it really becomes a problem is when you build up new surface film and the flat spots still remain.

I have a theory about this. When you start applying the TO, you do get a little penetration into the pores/structure of the wood. This alters the physical characteristics of the wood - basically locks the fibers together. From that point on the penetrated wood will demonstrate a different effect from sanding/polishing than the raw wood.

If you continue on, building film thickness, levelling, polishing, etc and never again make abrasive contact with the surface of the wood you will not have a problem.

Conversely, if you do sand/polish down to the actual wood, but do so evenly and everywhere, you also do not have a problem.

The problem occurs when you contact the wood in only a few spots. When you do that those areas sand/polish to a different effect - and because the effect is in the wood it will remain no matter what you put on top of it.

The only reliable solution I've found is to sand/strip everything down to bare or near bare and start over again. Try to spot sand it down to bare wood and all you'll do is make a ring at the transition zone.

Great insights, guys. Keyser, I hope I have ventured into area but that scenario describes my case pretty well. Multiple coats on top of the dull areas did not seem to help. Ugh - I was hoping I didn't have to sand it all the way back.