Black Cherry Sapwood Stain

Re: Black Cherry Sapwood Stain

Mike Schwing from Maryland

>Ralph, my guess is oxidation of wet sapwood. It continues to occur any time you expose wet sapwood. With cherry it is very noticeable. Slightly more so with pin cherry than black cherry. Its even more so with pear. It will occur even if you wrap the freshly exposed sapwood in plastic almost immediately after cutting.

I can think of no way to prevent it from occuring. When turning woods that do this, you have to be REALLY sure they're as dry as they're going to be before finish turning them, otherwise the problem continues to occur, darkening as soon as you make your finishing cuts.

Pear is REMARKABLY difficult to deal with this in this fashion. Even the heartwood reacts that way.

Good luck, and hopefully someone does have the answer you (we) are looking for.

Re: Black Cherry Sapwood Stain

Doug Trembath

>Ralph, I have been evaluating Cherry a lot since I moved to SW PA, and finally have an abundance of it to work with. I have found that the sapwood will immediately begin to degrade when fresh surfaces are exposed to oxidation. What I have done is to turn the wet cherry quickly, and to a thin wall. By the time I have finished sanding, the surface of the wood is pretty dry, but understanably still has moisture in the cells that needs to come out. I have been using a 1 to 2 pound cut of shellac sprayed on immediately after sanding to seal the surface. This has given the best results so far in my trials. Now, as the saying goes, nothing is forever, and I fully expect the color change to continue, simply as a function of the natural darkening of cherry as it ages. I know of no way other than bleaching to enhance and maintain the contrast and color differential between sap and heartwoods in any species. Most of us have come to understand that wood is maybe the most dynamic of the materials used in craft, and over time its appearance and characteristics will continue to change. I've come to accept this, and simply enjoy the fact that the wood often is the most beautiful for the turner alone.

Doug Trembath

Studio in the Woods

Re: Black Cherry Sapwood Stain

Whit

>A couple thing I've found about Black Cherry:

If it's green (or dry for that matter), there's a lot of sugar in the wood. Anything that heats up the wood will cause the sugar to carmelize, (a cooking term, I think, turn brown and thicken) and "stain" when sanding. It must be sanded very slowly. I run the lathe at 250 RPM (my slowest speed) and, when power sanding, run the sander as slowly as I can. A fair amount of pressure, slowest speed.

Secondly, if stain does occur, gently scrubbing down the heartwood with lemon juice after sanding seems to help. Don't exactly know why.

Re: Black Cherry Sapwood Stain

Doug Trembath

>What you're experiencing here, Whit, with the lemon juice, is the removal of tannic acid, which Cherry is full of, maybe even more than the oaks sometimes. This is a regular contributor, and I believe, is much of what assists in the darkening and staining of the wood in general. exposing these extractives to Oxygen stimulates the staining process, much like rust resulting from O2 and iron.

As far as the burning of the extractives, that is a good point for those who haven't experienced the scorching of Cherry by heat. I don't get scorching in my sanding, but have had sufficient experience with it while milling flatwork in dry wood. I have, though, held my gouge in the same place too long with the back of the bevel rubbing, and burnished a line in the wood. That's of course the same effect.

Doug Trembath

Studio in the Woods

Re: Black Cherry Sapwood Stain

Whit

>Thanks, Doug,

I suspected something like that but I didn't realize Cherry was that high in tannic acid. I had to make a test. I tasted, yes, tasted a piece of very green Cherry and, sure enough, high tannins.

A sanding point relevant not only here but elsewhere, as well. If the sandpaper feels hot the woods is a lot hotter and may well be scorching. You have to back up a lot of grits to get rid of the burnt wood. Thus, slow and slow. With fresh paper. As someone said elsewhere, use sandpaper as if someone else was paying for it.

Whit

Re: Black Cherry Sapwood Stain

Whit

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