How can I enhance walnut figure contrast?

[Peter Wilcox]

Thanks David. Your use of the phrase "limited penetration" clarifies the problem for me. Unfortunately, it probably means poor durability also.

[Todd Stock]

Might look at some college-level course notes for optics course, as well as lit for high index optical materials for lenses. In general, anything over 1.5 is considered high index, with some plastics close to 1.75 (makes for thinner lenses). The idea behind using a higher index transparent material as filler and sealer is to bend more light and get more internal reflection. Suggest that the interested craftsman can easily make up samples in figured maple and mahogany, then try out a couple methods. My experience (and my customers) suggest that epoxy and nitro give the deepest apparent depth and the biggest pop, but YMMV.

[Peter Wilcox]

Thanks Todd. I do have a certificate in optical fabrication, and I've made a number of telescope mirrors and lenses, so I'm familiar with refractive indices as they relate to refraction and dispersion in optical systems, but am having a hard time relating this to a wood/finish interface. It seems to me that the refractive index of the finish may affect the chatoyance of the surface, but in the walnut samples I've described above, there has been no significant difference in the macro contrast of the figure, which is what I'm going after.

[Todd Stock]

Ring porous wood have larger pores and - depending on grain orientation - longer path lengths, so I expect and see more difference in apparent depth and reflectivity versus paste or other less transparent fillers, On diffuse porous woods like cherry and maple, there is less change with change in filler or sealer - even with fairly strong figure, so not as much to be gained. Probably best to just opt for sticks with more apparent depth/deeper figure. I had to source some ridiculously figured birds-eye for the board and rosette to try to match the apparent depth of the curly ash back and sides on the pictured 000...diffuse woods just don't pop as well as stuff like mahogany or ash, so when mixing materials, things get interesting.

No formal background in optics, other than what anyone picks up as an aerospace engineer working electrooptics for UAV and surveillance platforms. Wonder if we have any PhD physics/optics guys that might point to something beyond the FPL work on figure and finish?

[Peter Wilcox]

I think I may have an answer to my problem. From the current thread about shellac not sticking to a spot:

It is unclear from your photo due to the "hot spot" of reflected light, but you mentioned sanding with very fine grit. That can 'polish' the harder areas of the wood, like the hard late wood, and that can cause stain resistance because the color can't get in.

And from this thread:

There has got to be some way to replicate that with a finish by limiting penetration but we're not there yet.

Putting the two together, I sanded to 220, then sprayed a coat of lacquer (Deft rattle can). Then I sanded back to wood and up through 1200, giving the wood a burnished, almost polished appearance. Then sprayed another coat of lacquer. The contrast is definitely improved (on the left).

I tried dyeing before the first coat, but the dye darkened the pores.

Thanks, David and Michael. I knew you guys could figure it out.

[David King]

I didn't figure nothing out, I just restated what you were asking for in your original post. I'm glad you figured out a trick that works. I think it might be what violin makers do everyday with their egg whites and waterglass.

[Barry Daniels]

Sorry, but I consider Deft to be an inferior finish. Hope it works for you.

[Peter Wilcox]

Sorry, but I consider Deft to be an inferior finish.

So do I - it never really hardens. I used it once for my first lacquer finish almost two years ago, and I can still dent it with a thumbnail. This is a left over can just used for this test, and I only mention the name for completeness. I can't spray lacquer in the winter as I have to do it outside, and sub-freezing temperatures are not compatible with its use.

[Michael Lewis]

Gloss lacquers will be harder than satin or matte due to the added ingredients to make those surface textures.

[Peter Wilcox]

Here's some followup on this experiment. Both were sanded to 220. The one on the left was filled with Zpoxy, then sanded back to wood, and then to 1200. The one on the right was sprayed with a coat of lacquer, then sanded back to wood and to 1200. Then both were finished with lacquer (about a bazillion coats on the right, to fill the pores. )

Although both were made from the same piece of wood, longitudinally adjacent, I think most if not all of the difference (darker on the left) is from the wood, not the finishing technique. Of course I can't be sure, since there is no control, but I like to think that the contrast was somewhat enhanced by the technique, and they both have a nice perceived depth to the figure. I still have enough wood for two more guitars, so maybe I'll get around to using it again someday.

[Mario Proulx]

Nice!

[Bryan Bear]

Well done.