View Full Version : One wood - three questions... bubinga

06-20-2010, 05:28 AM
The weather around here has been so unpredictable lately that we've had to put aside the cherry/walnut until things brighten up. Everything's ready to put together, but we don't want to do the joining with the humidity constantly fluctuating between 40% and 80%.

So, we pulled out a cigar box just to keep the tools warm and we decided to use some bubinga on it, for the back and the fretboard - and maybe also the headstock veneer, haven't come to a final decision about that yet.

13834 13835

As you can see, this stuff is flat sawn, but I'm not really concerned about that. What bothers me is the extreme graininess and to some degree also the grain runout. I know there's not much we can do about the runout, but the grain... So here are my questions

If we wanted to fill this deep grain on the outside of the back, what would be a recommended method? I have the feeling that the shellac/pumice would look blotchy in these pronounced grain lines.
Of course, the grain on the inside of the back is exactly the same and I’m thinking that might not be so good in terms of sound reflection. But does anyone really grain fill the inside? And if so, what do you use?
On the fretboard the grain is also an issue. We normally just wipe our fretboards with sesame oil, but in this case I’m afraid the grain might bother us. Any ideas?
EDIT: Note that the fretboard piece hasn't been smoothed yet - I just included it because... Well, it was lying there on the table feeling ignored and unappreciated.

Thanks in advance for the feedback.

06-20-2010, 10:23 AM
As far as pores go, my choice is WEST Systems epoxy, but that's just me. On the inside I wouldn't worry. You most likely haven't seen Raintree or those in the USA may call it Monkey Pod, but it has absolutely huge pores that run through the wood like tunnels.

Pour metho on one side and it runs right out the other. Jeffry Young in Singapore builds with it almost exclusively and has won the Healsburg blind listening test with his guitars, and they aren't pore-filled on the inside.

06-28-2010, 08:50 PM
Thanks Allen. I think Pete Howlett said something about the pores in mahogany being good for sound transmission, but the bubinga pores are a lot bigger. My concern was that if the back is acting as a reflector then a perfectly smooth surface would be preferable. Anyway we decided to just smooth polish the inside of the back with no filler or finish. So thanks for the advice.

Epoxy filling was one choice that, for various reasons, we haven't considered and probably won't any time soon. We decided to go with a tru-oil fill - sounds crazy but it turned out really nice. We tried the tru-oil sanding method that Ken (Timbuck) suggests, but we liked the results better without the sanding dust so that's how we did it, just buffing between coats. I'll post some pics soon.

06-29-2010, 11:14 AM
We tried the tru-oil sanding method that Ken (Timbuck) suggests, but we liked the results better without the sanding dust so that's how we did it, just buffing between coats. I'll post some pics soon.

Can you describe the difference? I'm just starting my first build with some mahogany salvaged from a wardrobe, and the pores are big enough that some kind of filling will be required.

Doe the tru-oil eventually fill (or cover the ends of) the pores? If so, how many coats (approximately)?

What was less good about the pores+dust look?

06-29-2010, 08:48 PM
Does the tru-oil eventually fill [...] the pores? If so, how many coats (approximately)?

What was less good about the pores+dust look?

The tru-oil dries and hardens very well - at least it did in the warm, dry weather we had last weekend. I rubbed the coats on with my finger, pushing it into the pores, then waited 2-3 hrs between coats and buffed with an 800 grit sanding pad. After about 4 coats the finish was just about what I wanted but it had a few finger prints in it, so I put one last finishing coat on using a polishing cloth and mixing the tru-oil 1:1 with real turpentine. Done! There were still some slight grain lines visible in the otherwise glossy surface, but we all liked the way it looked.

With the sanding method I rubbed the tru-oil on (on a different piece) with a 280 grit sanding pad. It filled and dried very quickly, practically while you were sanding, but left a coat of tru-oil/sanding dust residue on the surface that took quite a lot of perseverance to sand back down to level and smooth. I tried wiping the residue off immediately, but it was just drying and firming up too quickly. The deep pores in the bubinga were almost completely filled with the one coat, so I guess two would have done the job - but it didn't look any better than the piece I was doing with just tru-oil and it took more effort and time working on it. Granted, I may have been doing something wrong, but how tricky can it be?

BTW, boiled linseed oil is listed as the main ingredient of tru-oil, but in my experience it is much harder to work with and get such good results. It doesn't cure as well and the typical linseed oil smell stays in the wood for months.

Michael N.
06-29-2010, 09:20 PM
I'm surprised you filled pores with a few coats of Tru Oil alone. I'm fairly certain that it would take a huge number of applications to completely level fill. Over time the stuff will shrink back somewhat and your pores may not look filled at all.