Fill and Finish for an Inlaid Walnut Cutting Board

Walnut is an unusual choice for a cutting board. Here are thoughts on how to finish it. April 21, 2008

I am looking for some suggestions for knothole filler for a walnut cutting board. I was planning on finishing with a few coats of mineral oil but I am open to other suggestions.

Forum Responses
(Finishing Forum)
From contributor A:
Is this just one board and one knot or are there thousands of them? I think I would make a decorative wood inlay to cover the knot if there is only a couple.

From the original questioner:
The cutting board is 11 inches x 20 inches - five 2-1/4 inch rips that were glued together. There are about four knots, and all of them are smaller than a dime. There are also two wane voids 1/8 inch x 3 inches. I tried to fill with pigmented pc-11 epoxy but it pulled out when I ran it through the planer. I make concrete countertops and sinks so I am a little out of my realm when it comes to cutting boards.

From contributor B:
A lightweight mineral oil will be fine as long as you and your customer realize it will take frequent renewal of the oil. You can also use pure tung oil which is food safe once dry, if the clients have no nut allergies. Paraffin is also used to protect and you can get it at the grocery store. Behlens has a non-toxic salad bowl coating as do a few others. Beeswax will work also.

From contributor C:
As far as I know, walnut is somewhat toxic, and no dust or shavings can be used in animal bedding. Not sure I would make a cutting board out of walnut. You might want to investigate further.

From contributor B:
Contributor C has a point - walnut can be an irritant to some people, an allergen to other. Anyone who is allergic to nuts may have difficulties with a walnut cutting board or eating walnuts or using walnut oil in cooking or other food use. It's best to check and know your clients take on this.

From the original questioner:
A local planer told me a rumor about a horse that died from bedding down in walnut shavings. He didn't want to take any chances so he spent two days cleaning out his equipment before he resumed supplying shavings to a local thoroughbred breeder. He also wouldn't run my walnut. The people that I am doing the board for are only at their Montana cabin three weeks a year. I realize that walnut is not ideal for cutting boards but it is a decorative inlay in the countertop and it is from the client's native state of Virgina.

I was a little concerned about the open pore grain structure and was leaning toward the tung oil finish. I was wondering if it would help out with filling the wood grain or if I should count on salmonella as a filler?

From contributor D:
Contributor B mentioned the easiest finish - walnut oil.

From the original questioner:
I am not so worried about easy as much as the best finish. The inset cutting board is the crown jewel to his 10,000 dollar kitchen countertops. It has a dastilbe fossil under it.
I am leaning toward tung oil to get more of a darkening on the unsteamed walnut followed with maybe a carnauba/beeswax blend because that is what I have in the shop. I was hoping for a little grain fill from the wax. Most people put a solvent with the tung, I think to help speed up the drying. I probably do not want to do on a cutting board. How long will pure tung take to dry at 70 deg. F.?

From contributor B:
Pure tung oil will take a good week or longer to dry. Depending on how many coats you use, it could take weeks to finish with pure non-polymerized tung. Tung that is polymerized will take a few days per application and one that has siccatives/dryers as little as 6 to 8 hours. Thinning tung does not speed up the drying - only metallic and calcium dryers will afford faster dry. The problem with using wax over a cutting board is that the customer will have to remove the wax when ever it needs to be renewed with fresh tung. I suggest you leave this out of the equation. Even though it's a good method for furniture and floors, it is not so smart for a cutting board surface. After applying tung to end grain (several coats), it can be filled with paraffin wax to more permanently seal off the pores for longer service.