Steaming walnut question

Re: Steaming walnut question

Bill Tindall, E.Tn.

Walnut must be fresh cut to do well. The wood is heated in wet steam and when it reaches about 200 F the sapwood turns nearly as dark as the heart wood. I have done small pieces in the pressure cooker.

Re: Steaming walnut question

Barry Irby

This is probably not worth the effort. I am working my way through the pieces that have sapwood on them from some I had cut about ten years ago. It's air dried. I just ran across a couple of pieces with really nice curly grain. Not big enough for anything much though. Maybe I will give it a shot just to see what happens.

Color?

Dick Coers

Is the color change a result of the heat and steam, or is it a leaching of heartwood color into the sapwood?

heat and steam

Bill Tindall, E.Tn.

I occasionally helped a local walnut steaming operation. It was "common knowledge" there that the steam dissolved the colored stuff and diffused it to the sap wood. The lumber to be steamed was dead packed to get good contact between the white sapwood and dark heartwood.

I provided this common knowledge on some Forum and was promptly buried by the wood expert John Arno with contrary technical information(1) on what really happens. Skeptical, in spite of the technical papers supporting the heat and steam process, I put a piece of sapwood in the pressure cooker and sure enough it began to darken once it reached near the boiling point of water. I planted a walnut tree in memory when he died.

1. L. L. Johnson, Forest Products Journal (1966) pg 525.

Re: heat and steam

Don Stephan

Thanks for sharing your finding. I too had read more than once that steaming moved some of the color of walnut heartwood into the sapwood, as an explanation for alleged decrease of color intensity in the heartwood. Is it possible that steaming decreases some of the heartwood color intensity without leaching it out of the heartwood?

Re: heat and steam

Bill Tindall, E.Tn.

I have planed thousands of bdft of steamed walnut and I have not observed a decrease in heartwood color. Several thousand bdft of walnut will go into the steamer. Some color runs out in the condensing steam, but it is an insignificant amount.

In steaming the condensing steam does extract color from the heartwood. This colored water must do some staining of the sapwood but the depth of staining would not penetrate to the center of the lumber.

Re: Steaming walnut question

William Duffield

There is an alternative: Staining the sap wood. Of course, it has advantages and disadvantages. First, there is the skill required to mix the stain to match the color of the heartwood (unless your stock don't have any heartwood). Some of the colors of the heartwood are fugitive, and will fade away over the years, while pigment stains in general will not fade. Steaming also destroys the fugitive colors.