MIMF

I've made a couple of walnut tops. I noticed when I cleaned with naphtha that when wet, the color was fairly dark and low contrast, as I assume it will be when sprayed with lacquer. However, as the naphtha evaporated, the engrain portions of the figure stayed dark (wet) as the flatgrain portion dried first and lightened up. Is there a way I can incorporate this into the finish, say by sanding back the first lacquer coat, and then applying another coat of a finish that isn't absorbed as well to keep the wood lighter, or possibly bleaching before applying subsequent coats of lacquer? I realize whatever I do will have to be on scrap first.

The pics show dry, wet, and partially evaporated surfaces.

If you have some scrap wood for tests you could try a weak mix of light brown trans tint dye. It will probably darken more anywhere that is end grained. Dye can enhance the figure of some woods without changing the color very much if you can find a good match.

Using dark brown tinted pore filler really brings up the contrast of the grain.

This is my schedule on Walnut:

After sanding up to 150 grit fill the grain with a dark filler. Sand up 320, reapply filler and sand until everything is level. Dye the whole surface with a bright yellow or orange dye. This will neutralize the sapwood and pops the grain later in the process. I use the Transtint water base dye. Dry for a few hours and sand gently w/320 leaving the dye in the curl. Follow with a coat of amber shellac and smooth w/0000 steel wool or grey scrub pad. Apply a dark brown gel stain/glaze and immediately wipe off starting in the center before it dries. Dry overnight. Top coat. Practice this on scrap.

Darker walnut like that is tough. I remember hearing that back in the day they would boil the darker billets (green wood) in a 55 gal drum for a day or two in the back yard to try to get some of the tannins out of the wood. Probably too late for that treatment in this case. I'm not really sure what was accomplished but it sounded impressive to me. It took some pioneers like Breedlove a while to figure out how to work with the stuff.
I just dump West systems epoxy over it and hope for the best.

Oil based finishes really tend to accentuate grain as well.
Something like polymerized tung oil as a base coat might help.

Thanks for your suggestions. The problem is that the dark part of the figure is very dark already (almost black), so I don't think dyeing the wood will help. I need to make the light parts of the figure lighter to increase the contrast. So far I've tried Tru oil, clear and amber shellac, Z-poxy and lacquer. The best so far (marginally) is lacquer - sanding back and re-coating seems to help a little, though I can't explain why - maybe placebo effect. I've still to try polyurethane or a wiping varnish.

But I need to fill the grain - can I apply epoxy over lacquer, and then more lacquer over the epoxy?

Peter Wilcox wrote:can I apply epoxy over lacquer, and then more lacquer over the epoxy?

That does not sound like a good idea. You would likely have adhesion issues.

If you don't mind losing a little depth to the figure you can try a water based varnish that won't darken the wood as much.

How about an aniline dye with lacquer sealer/topcoat? I've use that many times on furniture and it always seems to do the trick in making figure pop.

Peter Wilcox wrote:The problem is that the dark part of the figure is very dark already (almost black), so I don't think dyeing the wood will help. I need to make the light parts of the figure lighter to increase the contrast.

That is simply not possible. You can bleach the wood but that will make everything lighter. Any dye, stain, or finish you use will darken the wood overall. You will have to live with the darkness, but most people think walnut is a beautiful wood regardless.

Unfortunately, I think you are right, Barry. I tried stuff I have on hand - polyurethane, Minwax "tung oil finish" (not tung oil, I know - apparently a wiping varnish), KTM9 after dark dye and sanding back, to see if waterbase would leave it lighter, and even soaked it in 3% H2O2 overnight - really no difference in any of them regarding contrast.

So I guess it's going to be grain fill with Zpoxy and spray nitrocellulose lacquer clear coats as the easiest way with the best result I know of - it will look nice anyway, even if dark. They're not ready for finish yet anyway, and I'll have to wait for spring weather since I have to do it outside. Thanks for everybody's suggestions.

Looks to me like some pretty amazing wood. I think you'll be fine as long as you don't darken it so much you can't see anything.

If you are going to do a nitro finish I'd be tempted to skip the z-poxy and just grain fill with nitro, assuming you have the time to let it shrink back.

Epoxy filler has a fairly high index of refraction, which provides greater contrast than lower index clear fillers, and has less in the way of shrinkage issues than finishes used for the job. CA is another higher index filler, but may be both more noxious and a little more difficult to handle on large surfaces.

Air dried black walnut shows a diversity of color under finish that is destroyed by the steam-kilning used to even out sapwood and heartwood coloring...this color variation of greens, pinks, and violets can be duplicated with dye washes or careful airbrush work prior to filling, but it is touchy work ensuring the color is not sanded out, or lifted/redistributed by the filler.

Todd Stock wrote:Epoxy filler has a fairly high index of refraction, which provides greater contrast than lower index clear fillers, and has less in the way of shrinkage issues than finishes used for the job. CA is another higher index filler, but may be both more noxious and a little more difficult to handle on large surfaces.

Hard for me to find any data on the refractive indices of finishes, but it looks like lacquers and shellacs are in the 1.50 to 1.51 range, the common epoxies at about 1.55, and cyanoacrylates from 1.45 to 1.5. Do you have any links or info on this, and particularly how the refractive index of the finish affects the apparent depth or contrast of the figure?

I'll apologize in advance for this not being a guitar, but it's guitar shaped...

This is Walnut crotch finished in Nitrocellulose lacquer but the wood was scraped, not sanded. There is no dye or stain. I think the contrast is pretty decent on this although it shows up better in person than these photos indicate. I just made this a couple of months ago.

That is a lovely finish. I guess I'll go out and scrape some scrap to see if that helps.

David King wrote:If you are going to do a nitro finish I'd be tempted to skip the z-poxy and just grain fill with nitro, assuming you have the time to let it shrink back.

Why would you skip the filler? I tried filling mahogany with lacquer - I'll never do that again.

David Falkner wrote:This is Walnut crotch finished in Nitrocellulose lacquer but the wood was scraped, not sanded.

Scraping gave me the same results as sanding. I just have very dark wood.

Peter, skipping the filler was a way to have just one index of refraction. Sometimes that extra clarity looks better sometimes not. I agree that it's not the most efficient process. In your original post you mentioned how you wanted to capture that moment where some of the mineral spirits had flashed off and you had the best contrast. There has got to be some way to replicate that with a finish by limiting penetration but we're not there yet.