Finishing with Tru-Oil

[Wasted4440]

Hi everyone,
In about a month or so, my current bass build will be ready for finishing, and I was thinking of doing the entire thing with Tru-Oil, roughly following this video: .
I have a five piece body and neck as seen below, with the neck being maple-mahogany-walnut-mahogany-maple and the body being pau ferro-maple-mahogany-maple-pau ferro.

Once sanding up to at least 320, I plan on removing any oils with acetone and then applying the tru-oil in thin coats, almost like a french polish. After maybe 30-40 coats with occasional sanding with 600 to 1000 grit. After drying for some time, I'd like to polish the finish to a decent shine. I have a few questions before I start:

1. Should I use Tru-Oil as a grain filler as seen in the video, or should I use a dedicated grain filler? I'm a bit worried that in doing so, some color might transfer from the darker woods to the maple, therefore staining it. If a true grain filler is the better way to go, does anyone have any suggestions as to which one to use?

2. How many coats do I need to apply to build up a significant layer to polish? Unfortunately, I will only have about a month to do the finishing until I have to leave the shop I'm currently working, so I may have to wait til later to polish. Does anyone have any suggestions about what polishes to use and how to go about polishing with minimal equipment such as a power drill or just doing it by hand?

I bet I'll have more questions as the time approaches, thank you for your help!

 

[Jon Clegg]

As for 1. I used wet-sanding with tru-oil as a grain filler on the bass in my avatar. I had the same concern that the walnut might stain the maple; didn't happen.

As for 2. I ended up doing about 10-12 coats(? I lost count). Used a buffing pad with a power drill to polish. YMMV. You will want to let the final coat cure for about a week before polishing, so the move shouldn't be a problem.

That bass should look glorious once it's done.

 

[Geoff St. Germaine]

You'll find a lot of different techniques for applying tru oil.

I've done pore filling with both the tru oil method and using System 3 epoxy. I much prefer epoxy as it takes one application (walnut) and then the tru oil can start going on. Using the tru oil to fill pores on wood with large pores takes a lot of coats. You can get into the slurry method, which is faster, but when you have different woods next to each other you can discolour lighter woods this way. If you use epoxy you have to be sure it is compatible with tru oil. Not all are. If they are not I've read of people using a wash coat of shellac. Testing on scrap is the way to go.

IME, 30-40 coats is likely 2-4 times the number needed. I've had good luck with 10-12 and achieving a semi-gloss with little polishing. I use steel wool between each coat and level sand every 3-4 coats with 800 grit.

 

[Manton Customs]

The shine will be there before polishing, the purpose of polishing is to remove fine lint, bubbles, fingerprints and generally give the finish a more uniform look (a polished surface will refract the light differently, though not necessarily any glossier).

1, Whether you use grain filler will depend on how porous the wood. From what I remember when last using Pau Ferro it is fairly fine and not too porous, so I think you'll be ok to skip a dedicated grain filler, but it could be wise to do some test pieces. If you did decide to use a grain filler, simply mask off the Maple to stop any cross contamination.

2, Around 15 coats or so should be plenty, maybe less, you'll be able to judge as you go. I polish finishes like T.O by hand with Micro Mesh starting at about 3200 (don't start at the bottom 1500 or you may risk sanding through) then finishing off with buffing compounds. Whatever you do, give it at least 2 weeks to cure. It may be touch dry after just 24 hours but it takes a long time to fully cure.

I also use 0000 steel wool in between coats but make sure you buy yourself a tak cloth, it's an essential bit of kit for oil finishes.

 

[Robert Canfield]

Please post your final results. We would love to see (and hear) how she turns out.

 

[Wasted4440]

Thanks for the replies everyone. I talked to a gentleman I know who's been building acoustic guitars for decades and he suggested exactly what you said with the tru-oil. To seal the grain however, he suggested the method that was brought back to my memory, where you use a light, 1lb cut of shellac and after applying it to your finishing rubber, you sprinkle on a little pumice and rub that in to help fill the grains. However, the 4oz of shellac flakes I need are harder to come by for me than simply ordering off of Amazon, so I was wondering: Does anyone have any experience with Birchwood Casey Sealer and Filler?