Deciding On The Finish

One of the reasons it took so long to decide what I was going to order, and how much the final project was going to cost, was in the finish of the body. For me, the project was as much focused on the wood used in construction and showing it off to best advantage, as it was about the sound of the instrument. The aim was a fabulous sounding, as well as fabulous looking bass guitar.

It would have been great to have the body finished in a urethane gloss that leaves the wood looking like it has been dipped in molten glass, but for Warmoth to do it would have added hundreds of dollars. For me to try it was asking for trouble. Also, I learned that the traditional guitar finishes of cellulose and urethane can be quite difficult to repair if (when) they get damaged. The research for the alternatives in high grade wood finishes then got underway

Almost immediately the subject of natural oils, such as tung oil and Danish oil, came up. The more information I uncovered, the more clear it became that tung oil was a very forgiving product to work with. That is, you are unlikely to make a total hash of the work piece with tung oil. That sounded like it was made for me. The other attraction is that tung oil is completely natural and non-toxic, as is it's solvent, terpene. In fact, the literature says that it is often used on products that come into contact with food, such as a fruit bowl, or kitchen bench tops.

The finish of tung oil is a natural satin. It is easily repaired, and blends well with the original application. A low sheen surface can be created using a finishing, or rubbing, oil over the top of the tung oil. Similarly, there is nothing to prevent using beeswax and buffing that up to a nice shine if that's the result you're looking for.

As in many projects, the end result is dependent on the preparation done before hand. In the case of a fine wood finish, the better the starting surface, the better the result at the end.

I selected for the body, a particular piece of Bubinga laminate for its beautiful, symmetrical figure and had every intention of making it the centre of attention. While I waited for the kit to be manufactured and shipped over to Australia from the U.S., I started practising on a piece of what I think is walnut veneer from an old bedhead. The existing stain and varnish finish was stripped off using a very coarse grit on a power sander. I then cut the piece into four sections so that I could compare results of different approaches to finishing. The power sander was put away and all the test panels were finished by hand.

400-Grit Sanded Finish

The first panel was worked up, grade by grade, to a 400-grit finish. The result was quite good, considering the state of the veneer before I started. The surface was smooth and the figure was starting to emerge very nicely. This was my baseline sample.

On the second sample, the sanding finished at 1200-grit paper. This was where it became clear how important a fine finish can be to the end result. Once you get up to about 800-grit, the figure in the wood really starts to pop out. By the time I finished the sample at 1200, the surface started to develop a polished sheen and the visual depth so desired in figured timber.

1200-Grit Sanded Finish

And this is when I learnt a new word - chatoyance. Chatoyancy in wood is the property whereby the finished surface reflects light differently depending on the angle from which it is viewed. This is a result of the wood fibres laying at different angles. Some will be parallel to the surface, while others will intersect the surface. Unfortunately, the photo can't really do justice to the appearance of the result. I was very happy with it.

At the time I was working on the panels I didn't have any 2000-grit paper, but that was the plan for the bass. With this kind of result for 1200-grit, it can only get better still working up to 2000, and with the application of the oils.


Tung Oil Over Sanding Sealer

An option I tested was tung oil over sanding sealer. This was to see if the sealer filled the pores and grain hollows to give a perfectly smooth finish.
The result of two coats of sealer before applying tung oil produced an OK finish in that it developed a shine fairly easily but it lost the touch of natural wood. It would have taken quite a few more coats to completely fill the grain, as well.

The key learning was by accident, literally. With the panel knocking around my work bench, before I tidied up properly, it acquired a couple of scratches and marks. These marks had chipped off the hard sealer, revealing the bare wood underneath. The damage would require sanding back the affected area, before re-sealing, sanding and re-finishing. I didn't try a repair as the experience confirmed that this was not going to be the best method for me.

        Tung Oil x 10               Finishing Oil Over Tung Oil

With the last panel, I started the multiple coats of tung oil. In the end there were ten coats of oil, with a light sand after a drying time.

With this particular veneer, after each coat, the surface fibres soaked up the oil and stood up, giving a stubbly feel. The sanding was at 1200 to knock the stubble off. By the last coat, a lovely golden glow had developed in the veneer, which is largely missing in the photo, unfortunately

Finally, I divided the panel with masking tape and rubbed in the finishing oil to one side only, to give a side-by-side comparison. The photo doesn't really highlight the difference adequately, but a shine and depth to the finish started to build after a only a couple of coats. The decision was made to go with a finishing oil over a solid tung oil base.

Testing the proposed finishing method certainly inspired confidence that I would be able to do the job successfully myself. It also confirmed that this method would produce a lovely, natural result that highlighted the beauty of the wood.

Satisfied, I waited for my delivery from Warmoth.