Preventing blue stain on sapwood in turnings?

[Bob Bouis]

We were talking about heartwood/sapwood contrast in another thread, and how some species' sapwood usually ends up stained a darker color, for me at least. Today, I was roughing out a green walnut bowl when I stopped for lunch. Came back an hour or two later and the formerly pristine sapwood was literally 100% covered with blue fungus. It wasn't deep, but it was there and surely would permeate it no matter what I did.

It's still 85 degrees here even though it's almost November -- that can't help. But short of drying it in the refrigerator (you can't actually dry things in the fridge...) or soaking it until February, what can I do to prevent the fungus discoloring my wood? Blowing out the loose water after finish turning doesn't really work. Bleach seems like a bad idea on walnut, at least for once-turned bowls.

In a fit...something...I grabbed some lawn fungicide (propiconazole) and mixed up a spray bottle and sprayed that on the piece. From a quick googling I see that it's actually used for that in commercial lumber applications, but always in a mixture with some other stuff. Obviously precautions will have to be taken when/before sanding. But does anybody have any ideas or suggestions in the fungicide vein or otherwise?

[Tom Brouillette]

Fungus or mold don't show up that fast. You are probably seeing the reaction of the tannins in the green wood when they contact metal. I get a "tannin tattoo" when I green turn certain woods. It takes days to wash away. I've read where some people put paper towels between the chuck and wood to minimize it. I never do. Whatever blue shows up turns away when I finish the piece.

[Bob Bouis]

It didn't just "show up"; I've been working that wood for a couple weeks. My entire shop is probably coated in the spores.

[Bob Bouis]

I'm sure of what it is. It's a light blue color, not black like tannin. Plus there's none on the heartwood. There were some spots of it on the log when I got it, near bark damage and cuts. Presumably when I turned the other pieces the fungus came off with the shavings. If it wasn't floating in the air, I wiped it all over the bowl while turning it.

For what it's worth, the propiconazole seems to be working so far. It didn't completely prevent the blue from forming, but it's just a few spots. Really slowed it down. All it has to do is slow it down enough to let the piece dry out--hopefully.

[Brice Rogers]

I think that a very mild solution of chlorine (bleach) would work. Swimming pools run around a 1 ppm solution to keep algae from forming. Try a teaspoon in a gallon. I suspect that it'll be plenty. I would doubt that a solution of that low concentration would lighten the wood at all.

BTW, when I've turned green Jacaranda (a local wood here), it turns orange in about 10 minutes. But it is very superficial and sands off. Perhaps your blue color is very shallow too.

[Larry Copas]

Does it look like this?

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Or does it have a lot more gray color? Does it appear immediately after the lathe cut?

[Bob Bouis]

It's got a greenish cast to it. Takes a couple hours to appear. It's superficial on a fresh turning but was up to about 10" deep on the log. I know what blue fungus looks like. Really!

Y'all are going to make me go grab my camera.

[Bob Bouis]

So... it's greenish blue when it's fresh and darker when it dries out. Here's some pictures. The first one was freshly cut more or less and was pre-existing stain in the tree. The second two formed after it was cut and had been treated with fungicide a few hours before. They might be damp from fungicide in the picture. The last one was older and had started to dry out but might be damp from fungicide too.

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[Tom Brouillette]

It didn't just "show up"; I've been working that wood for a couple weeks. My entire shop is probably coated in the spores.

you said in the OP it would show up in an hour or two.

[Bob Bouis]

Sorry--what I meant was that it showed up on that piece in an hour or two. I've been working on other pieces from the same tree, and some of them had it on them already. Presumably the clean piece picked up the spores from the shavings/tools/my hands.

[Jamie Straw]

Looks like mold to me -- we cope with it all year 'round here in the Puget Sound, and being in the middle of old forest land and leaf litter, the spores are ever present. If I'm turning green wood, I have to keep a bottle of mold/mildew killer nearby, or a bottle of 10% (perhaps less) bleach, nearby. Have to say, though, green is a rarity. I spritz the wood before I Anchorseal it, and if I have to leave it for any length of time during turning, it gets spritzed. It helps, but no complete guarantees. I wonder if you're pushing spores into the wood? After you turn through moldy stuff, and you're through that layer, you might want to clean off the tool with a countertop-wipe or rag with bleach/water on it.

[Leo Van Der Loo]

What I see, especially in your last picture is the regular discoloration that happens with Walnut, it is the color from the heartwood bleeding into the sapwood.

Just look at these pictures where the sapwood of the Black Walnut has stained from nearly white to the dark color.
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Only in this Black Walnut sapwood turning with nearly no heartwood at all, did the sapwood not change much as there was not enough heartwood and I dried it quickly.
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The Walnut logs that are used for lumber are often steamed to have the color bleed into the sapwood, turning it as dark as the Heartwood.

[Chris Gunsolley]

What I see, especially in your last picture is the regular discoloration that happens with Walnut, it is the color from the heartwood bleeding into the sapwood.

Just look at these pictures where the sapwood of the Black Walnut has stained from nearly white to the dark color.
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Only in this Black Walnut sapwood turning with nearly no heartwood at all, did the sapwood not change much as there was not enough heartwood and I dried it quickly.
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The Walnut logs that are used for lumber are often steamed to have the color bleed into the sapwood, turning it as dark as the Heartwood.

Bob,

I've turned a good amount of Black Walnut, and I think Leo is spot on here about the heartwood bleeding into the sapwood. I've had that happen on probably every Black Walnut bowl I've turned. It's just something you have to accept about working with this species, and I wouldn't worry about it because your end result will still look gorgeous. Here are a couple pictures of one of the first Black Walnut bowls that I turned:

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You can see the same exact phenomenon in the sapwood of this bowl as you can see in yours. It is not mold. The heartwood simply bled into the sapwood. And personally, I don't think it looks too bad. Here's another one I turned that demonstrates it even more, with the bottom of the bowl on the lathe before the bleeding occurred, then off the lathe after it occurred, after finishing it:

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These two pictures feature the same exact bowl. However, you see a lot more heartwood in its bottom in the second picture, after it was finished, than you do in the first, when it was just turned. That's for no other reason than the heartwood of Black Walnut bleeds into its sapwood. If you look closely at the second picture, you can even see the lines where the border of the heartwood used to be on the bottom of the bowl, at the earlier point in time in the first picture.

[Fred Belknap]

I have to agree with Leo and Chris. Most of what I turn is black walnut that I cut myself off my property. Cutting a walnut tree in the fall will work the best if you want to have a distinctive sap and heart wood bowl. It doesn't bleed together as fast because of less sap in the tree. Here is a picture of a walnut bowl that I cut in the fall, I think it was late September, and the bowl was turned fairly soon after it was cut.346708

[Bob Bouis]

I hate to be obstinate, but I still think y'all have it wrong. There are different things that can cause sapwood to darken, and I'm not going to claim to understand exactly how they all work. But color bleeding from the heartwood isn't one of them. What you're seeing is discoloration from a chemical process caused by prolonged high moisture content (in Leo's; this is like how steaming works) or a combination of moisture and fungus (Chris's). Chris's picture especially very clearly shows fungus that's grown in clumps. If you look at my first picture, you can see that the discoloration has started near the bark. It's not bleeding from the center out.

Heartwood holds moisture much longer and more stubbornly than sapwood, so if you have all sapwood it dries faster and whiter (like Leo's last picture). If you have heartwood and sapwood together, you get fungus growing in the sapwood at the wet spot where they meet, as in Larry and Fred's pictures. Maybe that looks like heartwood bleeding color after the fungus dies and darkens, but that's not what it is.

The fungus I'm talking about isn't a surface mold. It starts at the outside but it goes deep into wood, all the way through a log if you let it.

[Perry Hilbert Jr]

I cut some maple last January on a very cold day. I stacked turning pieces in the barn to dry and it was not until Late September that I noticed a ring of greenish mold around the cut ends of the wood. Perhaps an 1/8 to a 1/4 inch in from the bark. I have turned some of the wood and once I get below that layer of the wood, there is no problem with mold.

[Bob Bouis]

Results of the fungicide a day later seem to be...mixed. The little one that got it the fastest and the mostest seems to have the least staining, but...who knows? I guess we'll see in a month or three.

I am still kicking myself for messing up the biggest of the "spoon bowls." Somehow the coring rig got off course and wouldn't cut all the way through. So instead of cutting down the "handle" part and then getting back to coring, I tried to break it. It wasn't as close to being cut through as I'd thought (and tearing it is a big no no with crotches for reasons that ought to be obvious.) It tore the fibers in a spot at the center and cracked the "handle" to boot. Ah, well. If I do a film finish it won't be too noticeable.

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[Bob Bouis]

The first pieces I turned from this tree all have blue rings where the heartwood/sapwood meet. The ones I sprayed with propiconazole don't. It may not have been long enough for it to develop, but the result so far is encouraging. It did not completely prevent the sapwood from darkening, but it's better than in the untreated ones.

Propiconazole's not really a great fungicide for the lawn or garden; there are better ones out there. But for some reason it's pushed by the home centers and the like. Maybe because it's safer? You read about how it's used -- treating lumber, paints, some food crops, etc. It's used as a wood preservative, too, so maybe it's just the thing for this application. I am going to start spraying everything I turn with it and mixing some in with my anchorseal. Why not? I got ten bottles for $2 each off the clearance rack at tractor supply a couple years back. Even at full retail price it's pretty cheap.

[Jamie Straw]

The first pieces I turned from this tree all have blue rings where the heartwood/sapwood meet. The ones I sprayed with propiconazole don't. It may not have been long enough for it to develop, but the result so far is encouraging. It did not completely prevent the sapwood from darkening, but it's better than in the untreated ones.

I might try some on the next batch of green maple I get. Sure get tired of having much of it get gray spots/areas! Thanks for posting.