Help with mold and a pretty big crack!

[Cheryl A. Prince]

Greetings all. I sure could use your opinion on how to deal with two problems. First, the below two photos are of some black walnut bowls that I rough turned in March of 2010. I unwrapped them tonight to select a piece to finish turn and found that several of the bowls had thick dark mold around the tenon but no where else on the bowl:eek:. I took a stiff bristle brush and cleaned the mold off (over the dust collector) the best I could. I'm wondering if I should wash them off with something like mineral spirits to keep the remaining mold from going airborne when I finish turn them. Would there be something better than mineral spirits to use to clean them up? Any suggestions would be appreciated.
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My next three photo's are of a nice large (16") diameter shallow bowl or platter that has a pretty severe crack coming from the center of a knot. The crack wraps partially around the base of the tenon and I'm concerned about turning it, Should I try to fill the entire crack with something like epoxy and coffee or do you think I should open the crack a little and use CA glue with stone mixed in? I just don't want the thing to come apart whlie I'm turning and never having turned anything with a crack like this I'm not sure what to do. Thanks in advance for your help!
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[Dale Miner]

On the mold issue;
The mold is a result of the sapwood drying to slow. The surface, even though brushed, will still have spores present. Diluted (25 bleach/75 water) household bleach will kill any spores that remain on the surface better than mineral spirits. I'm not sure mineral spirits will have much effect on the spores. Another concern will be the spores that are released when the wood is turned. For that issue, the only real solution will be good ventilation and respitory protection while turning. Many people, me included, turn spalted wood that contains fungus. There are several thoughts on the effects that spalted wood has on humans. The mold on your pieces is a different variety than the fungus that occurs in spalted wood, and I would avoid breathing the spores as much as possible by using a good fitting high quality dusk mask and having my vacuum system operating while turning the areas that are suspect. Once the wood is turned and finished, any spores that remain in the wood will be encapsulated and will not pose a health threat. Walnut heartwood is virtually immune to fungal activity, but the sapwood is very susceptible. It looks at though the foot of your bowls were substantially thicker than the rest of the bowl when the tenon and false foot are included. Also, from the mold pattern, it looks as though they were set flat on the tenon. The extra thickness and setting on the tenon contributed to the overly slow drying. I have found that on wood that is prone to mold growth, that brushing the roughouts with a solution of boric acid dissolved in hot water before bagging effectively stops fungal activity.

On the cracked bowl issue; Life is short, wood is plentiful. The world needs firewood too. Turn another, you don't want to give away or sell a cracked bowl anyway.

[Bernie Weishapl]

On the crack I would sand to fill it with dust and apply CA. Or I will take sanding dust and epoxy to fill it. I am wondering if you are getting mold from having the bowls wrapped tightly. When I soak in DNA and wrap I always cut open the bowl portion. That allows some air movement and I have never had mold. Just a thought.

[John Keeton]

The crack in the knot wouldn't bother me, but the extension around the base/tenon would be a deal breaker. Wonder if you could jam the bowl, and turn a new tenon. Looks like you have a lot of wood in the blank. Might be worth a try to save it, as it is a very nice looking piece of wood.

I think the mold on the bases is due to setting them on the base to dry. Gravity has cause all the moisture to collect in the bottom against the concrete floor, where it gets trapped and mold sets in. I would think setting them upside down to dry, on a rack for air circulation, would be a better plan.

[Dennis Ford]

I would jam chuck the cracked bowl, turn the tenon off and attach a glue block.

[Joe Meirhaeghe]

I have only had a mold problem 1 time & I did like Dale suggested. I used a bleach solution & it seemed to work good for me. As for the crack I would use epoxy with some form of filler. I'm not a fan of CA for any kind of repair. CA will crystallize & break down over time. When I make some thing I like to use materials that will last for decades, & CA does not fit that bill.
You can always use a glue block for the bottom.

[Bob Rotche]

I will throw my 2 cents into the pot from a different angle. I think people often get too concerned about cracks. Wood is a dynamic material and cracks are going to happen sometimes no matter how careful you are about drying the piece. The odds that the crack in the tenon will cause complete failure resulting the bowl becoming airborn I would think are very slim. To me, the time commitment comes with the sanding and finishing. I would go ahead and start finish turning, see how its looking as you get close to final form (looks like a very nice piece of wood). If you don't like it, put it in the burn pile and appreciate the fact that you got some practice finish turning. If it looks pretty good (which I suspect it will), then decide if you want to fill the crack with something or leave it "au natural", which is a matter of personal taste.

[Reed Gray]

A knot like that one will crack every time. Guaranteed. I don't think it will present any serious problems when re turning as the crack runs through the knot, and not through the main part of the bowl or tenon. I would situate the chuck jaws so that they straddle the sides of the knot rather than having one directly covering the knot.

For me, I am getting more selective on what I turn. If I see a knot like that, I will avoid it, working on either side of it making smaller bowls rather than having to spend the extra time fixing the knot. I would expect a knot like that to still crack after repair. Maybe not right away, but eventually. The grain in the knot is at right angles to the grain in the wood, and given that wood moves, the two different grains will be at war for as long as the bowl lasts.

robo hippy

[Prashun Patel]

I'd remove as much of the mold as possible with a scrubby pad. Then I'd finish turn it. That crack does not bother me; I'd fill it in; by now it might be stabilized. Once the bowl is finish turned and sanded and left in the light, the mold should not return.

[Cheryl A. Prince]

I think the mold on the bases is due to setting them on the base to dry. Gravity has cause all the moisture to collect in the bottom against the concrete floor, where it gets trapped and mold sets in. I would think setting them upside down to dry, on a rack for air circulation, would be a better plan.

I think you're right John. They sat on the shop concrete floor for about a year and then were moved up to metal shelves for about a year. I guess the mold started during the first year on the floor. Now I've got to figure out where to move and store the 50+ bowls currently drying on the floor!

[Cheryl A. Prince]

Thanks everyone for the great advice! I will wash them this weekend with a bleach and water solution. I think I will try to finish turn the piece crack and all and then fill it with an epoxy and coffee mix (I've never tried epoxy before but there has to be a first time for everything!). I also will get the remaining bowls up off of their tenons. As per Reeds advise I will be more selective when I rough turn nicer pieces to help them be more successful through the drying process. You guys are great!