Walnut/ Maple Table Finish

[Aaron Cain]

Hey guys,

I have just concluded a walnut table that has some inlayed maple accents in the the table top along with maple slats that make a shelf at the bottom of the table. I have quite a few finish products and I am just looking for a recomendation on which of them to use. I am going for a look that highlights the contrasting wood tones. My first priority is to I keep the walnut as dark as possible. The second priority is to limit the amount of yellowing the maple will do years down the road.

Finish products:
100% Tung Oil
BLO
General Finishes Seal-A-Cell
General Finishes Arm-R-Seal
UV inhibiting Spar Varnish
clear spray on dewaxed shellac

Things I have considered:
1- Few coats of Seal a cell then few coats of Arm-R-Seal
2- BLO followed by top coat of 1/3 BLO, 1/3 Tung, 1/3 Arm-R Seal
3- 1/3 Spar Varnish, 1/3 BLO, 1/3 Turpentine
4- Sand in Mineral spirits/Tung Oil Mixture followed by top coat of 50% Arm-R-seal and 50% Tung Oil

I have never worked with walnut before and I would love anyones input
thanks
Aaron

[Jim Becker]

Skip the Seal-A-Cell if you choose the General Finishes product. It's something that puts money in their pocket without generating much of any benefit to you.

Walnut often benefits from a mid- to dark- shellac such as "orange" or "garnet", although you must use de-waxed shellac if you are going to top coat with anything containing polyurethane or that is water borne. But don't put it on the maple if you don't want to add color.

I work with walnut second only to cherry. My finishing preference for it is BLO, shellac and if needed a top coat, usually water borne acrylic. Of course, that's the same thing I do with cherry!

[Glenn Madsen]

So here's the challenge:

Walnut loves oil, and darkens nicely with it.

Maple's not quite so happy, as it also darkens somewhat with the oils. That's something you said you wanted to avoid.

If you can't keep the oil on the walnut and off the maple, then shellac is likely your best move. But it will look different than just an oil finish. Not worse, nor better. Just different. Make sure you get enough shellac on there, though. Spraying is neat, but less controlled than padding or brushing.

A good rubbing out with synthetic steel wool (white pads) and a nice clear furniture wax, will cut the gloss, and add a more oil-like feel to the piece. You'd probably like it. I did some cherry/maple nightstands that way for my son and daughter-in-law.

I prefer Zinsser Sealcoat, thinned somewhat with alcohol, padded on, rather than sprayed. Unless it's a HUGE piece, that is. Or some of the neat German processed ultrablond that Jeff Jewitt sells.

[Steve Schoene]

Your possibilities list includes two distinctly different kinds of finish. Choice 1 gives you a oil/varnish mix to pop the grain, one thin coat is entirely sufficient for this, and could just as well be BLO or pure or 100% Tung Oil. With Tung oil, you get a tiny bit less darkening and yellowing over time, though I doubt you wouild notice unless you had test samples side by side. Tung oil is very slow curing, so you should wait at least several days before top coating. The Arm R Seal is just a polyurethane varnish. It can be allowed to build a film on the surface and develop a sheen of Satin, Semi-gloss or Gloss depending on which flavor you buy.

Choice 2 starts with oil and then follows with a mix of two oil with an oil/varnish mix. None of these can be allowed to build any film on the surface. They should be applied, let to penetrate for a few minutes, and vigorously wiped off the surface. The finish will remain a satin in-the-wood finish.

Choice 3 is also an oil/varnish mix, must be applied in the same way as no. 2, so that it too is an in-the-wood finish. Spar varnish has negligible special properties in this context and would be thin enough that UV protections wouldn't be meaningfully effective, and what ever effectiveness there was will rather quickly deteriorate. Unless you like the smell of turpentine, it's slightly different solvent characteristics from mineral spirits will have zilch effects in the final finish.

Choice 4 is another oil/varnish mix with just a slightly different cast of characters that with so much tung oil it will just take a little longer to cure between coats. Will you see any difference between this and choices 2 and 3? Perhaps if you look critically at side by side comparisons. Sanding in tung oil has little effect on filling the walnut pores--since virtually all the "slurry" generated with the sanding will have to be wiped away when you wipe off the excess. The 50-50 mix of pure tung oil and varnish is likely to be a bit sticky to apply, so you may wish to add a little thinner. All of these top coats must be vigorously wiped off as well.

The maple will yellow (or orange) over time regardless of what finish you apply. All of the oil finishes will also darken over time. Shellac darkens dramatically less over time.

If you are adventuresome and at the same time careful, you could consider dying the table with potassium dichromate solution. This would significantly darken the walnut, but would have very little impact on the color of the maple. This is the best way to enhance the contrast between the two woods, without laborously pre-sealing the maple before dying or staining the walnut. The dichromate is quite poisonous so precautions must be taken. Potassium pemanganate would have similar but not identical effects. Top coating with blonde shellac will preserve the contrasts.

[Aaron Cain]

I am lucky I am a highschool science teacher and have access to Potassium dichromate.

I have been doing a little bit of experimenting with it but I have a couple of questions.

I have read that an accepted concentration from 3-40 g per L of water is accepted based on what I am looking for. I made a few different concentrations and found that anything more than 10g per L turned the maple an orange color. What do you recomend as a concentration. I can always use multiple coats.

Because this is water based should I sand between coats of Potassium Dichromate before I add a top coat.

Steve your a life saver I really like the results so far.
Thanks
Aaron

[Steve Schoene]

Your experimentation has probably given you better data than I can pass on. Remember, the reaction between the tannic acid in the walnut and the potassium dichromate may continue for some time. Overnight is often recommended. It's hard to give recommendations for the concentrations since the dichromate is only one of the reagents--the tannic acid in the wood can vary considerably so eqach situation may be unique.

Question: is the orange on the maple with higher concentrations the result of a reaction or is it the drying of unreacted dichromate on the surface? Presumably if it happened to be the later, it would be removed by rinsing with water, and given the toxicity of the unreacted dichromate it would something you would want to do.

[Aaron Cain]

Question: is the orange on the maple with higher concentrations the result of a reaction or is it the drying of unreacted dichromate on the surface? Presumably if it happened to be the later, it would be removed by rinsing with water, and given the toxicity of the unreacted dichromate it would something you would want to do.

the reaction is because of the dying effect of the unreacted dichromate. I was unaware I could wash the wood with water to get it off. Should I just avoid some of the maple parts all together. I can't guarantee that some will not splash on some of the parts. I will let you know how it turns out

[Steve Schoene]

The color you have imparted to the walnut shouldn't be significantly water soluble, but that's easy to check on your sample boards. Unreacted dichromate is likely remain water soluble.

I don't think you can plan to keep the solution off the maple, though with this stuff "spashing" doesn't seem to be a good idea. Think of how you would dream your students might do it, as opposed to how you fear they actually would do it.

[Aaron Cain]

The project turned out awesome guys thanks for all of your help!

A special thanks to steve for giving me the idea to use potassium dichromate on the walnut. I was going to post a picture of the table but I cannot compress the file small enough to put it on the forum. If anyone wants a picture just leave your e-mail address and I will send it to you

thanks again
Aaron