Safely sterilize bowl blanks, how?

[Rick A McQuay]

I have a couple people who want salad bowls out of spalted maple I've harvested but I feel they should be sterilized first. Googling produced very little but maybe I'm using the wrong search terms. Besides fungus, I'd like to make sure any critters that have bored into the wood are well dead.

 

Some options I've considered:

1) Denatured alcohol - expensive, also I'm not sure if the alcohol will leave behind any contaminants.

2) Poison - Bad idea for salad bowls

3) Microwave - I've read that microwaving long enough to kill things will also crack the blanks

4) Submerging in boiling water - Not sure that will kill everything

5) Soaking in soap/water mix - ditto, not sure if it will kill everything or anything

6) Kiln drying - well I don't have a kiln plus I don't want to crack the blanks and slow drying may not kill anything. Some people say that spalting fungus will die when the bowl dries but I'm not sure this is true, ditto for critters.

 

Any recommendations?

[Chris H]

I would recommend the first option.  #1 is expensive for a single bowl, but not for many bowls.  The alcohol is re-usable, so quantity needs to be considered.  Also, the alcohol is a great tool for expediting drying the blank, if that is something you are interested in.  Look for an air tight "Rubbermade" type bowl that is large enough for bowls you typically use ($10-$20).  Then buy your Denatured Alcohol in bulk! (~$20 /gallon).  Don't do the alcohol soak until the peice has been roughed out.  This will save lots of alcohol, and time.

 

 

All the alcohol will be evaporated before you apply a finish to the bowl (or it should be), and then the finish will also act as a barrier between any wood contaminants and the food.  It is not a 100% protection by any means, but it is a decent buffer depending on your finish selection.  

 

I don't know if this is the "best" way, but it has worked for me without any problems.  I have done several spalted maple bowls, and spalted oak platter. 

[Rick A McQuay]

I'll give it a try, thanks.

[duckkisser]

i would not make anything out of spalted that is eatable its mold growing on the wood that gives it the color so your looking at spores through out the wood and i would not want to eat mold spores.

[dwacker]

After its dry its dead. Its not a harmful pathogen anyways. You dont need to do anything beyond normal soap and water.

[duckkisser]

particle i have had multiple pieces of spalted lumber that if its not tightly sealed and it got wet the mold spors started growing again. fungis spores are very resiliant to being dried out. in fact there are a number of species that will grow and reproduce in a matter of hours because soon after it gets dry again and those drouts can last for years. in death valley there is a mushroom that grows like that and only is seen every 20-30 years.

[Mike Frank]

I agree duckkisser i knew a guy that had infections in his eyes from turning spalted wood

 

what about using bleach mixed in water and spray on the wood

[dwacker]

particle i have had multiple pieces of spalted lumber that if its not tightly sealed and it got wet the mold spors started growing again. fungis spores are very resiliant to being dried out. in fact there are a number of species that will grow and reproduce in a matter of hours because soon after it gets dry again and those drouts can last for years. in death valley there is a mushroom that grows like that and only is seen every 20-30 years.

 

Even if that were the case it is not harmful you could eat the wood with no harm. They are just an allergen and will not live through a basic soap and water bath just like any other dish in your house. We are not talking about the same spores found in death valley.  Part of the reason we kiln dry lumber is to kill any fungus and insects. Do as you wish but it is not necessary what so ever. We have been purposefully producing spalted wood for ornamental purposes for many years. The dust from working is your only worry. Active fungus would need a constant 30% moisture content to contain free water needed to survive.

 

From the US department of agriculture.

 

Caution 

Although the white rot fungi responsible for the decorative appearance are not pathogenic (a health problem), there might be some molds associated with the spalting process that could cause allergies in people. It is also possible that some pathogenic molds, such as Aspergillus fumigatus (responsible for farmers lung), might be present, so it is always a good idea to work in well-ventilated areas.

 

From us forest service. Kiln drying

 

 Tests show that a temperature of 150 °F

or higher for at least 24 h should kill all stain and decay

fungi.

[duckkisser]

and yet it doesn't always die off after a flood last winter I had 100$ of kiln dried spalted end up growing back and I didn't realize it and I was throwing up and had burning eyes and sinuses for a 3 weeks until I found the lumber and threw it out. now I have a sensitivity to pollen that I never had before. I had to bleach the area where the mold was growing from the wood onto my walls.   spalted is a great wood to work with and it can look realy cool but unless I know what kind of fungis is growing on the lumber I don't want to eat out of one. I have made a few bowls and boxes but I always seal it well and I tell the people that not to put water in that container since there is a possibility that the mold could grow back   

 

every quote you had was about killing the fungi that grow on the lumber nothing about the spores.  mushroom spores are a very hard to kill off since there  not really "alive" there just the "seed" of the fungi and can grow at anytime.  there are very few mushrooms that are deadly but a number will make  you very ill.  and who knows if your customers or who they serve food too will have a sensitivity to that type of mold or fungi.

 

McQ what ever you decide be careful when your sanding the wood that will definitely get you so wear a good mask and use dust collection even if its just your shop vac after I work with spalted my sinuses kill me.

[Rick A McQuay]

A person passed this along to me,

 

 

 

 

"spalted wood results from the activity of fungi and other microorganisms present jn wood. Microfungi and bacteria often produce pigments that stain but do not decay wood appreciably. White-rot fungi produce dark zo e lines in wood and can cause significant decay. once the water content falls below 20 tp 25% though, the fungi and microorganisms become inactive and eventually die. Although it is possible for the pigments to leach out of spalted wood, there is no evidence that this happens. spalted wood has no known health risks and should be safe to use for food containers and serving utensils." - Karen Nakasone, mycologist at the Forest Products Laboratories in Madison, Wis.

 

Fine Woodworking Feb 1996

 

 

[Tpt life]

Alcohol will break down spores, bleach will, vinegar will... I would not soak with any of them undiluted and would fear that bleach would lighten the spalted staining. If you are worried about spores then activate them first. Hit your blank with water, wait two hours, then disinfect. Repeat as desired.

[Chris H]

Well, I think we are possibly talking about two different things.  Live mold, and dead/remission mold.  

 

First, you absolutely can kill mold.  It isn't easy nor guaranteed, but there are many tried and true methods. (Heat, Alcohol, Bleach are all good options).  

 

If you subject any lumber to high moisture, spalted or not, you risk mold growing (potentially more dangerous kinds other than white rot too).  There are mold spores everywhere, on the lumber, in your home/shop...probably on the shirt you wearing right now.  They are dangerous when you grow them and subject yourself to massive influxes.  Spalted wood that has been treated in someway will not generate those quantities, unless you go out of your way to encourage it (high moisture, dark storage).  Mold is an allergen, so each person will react differently.  

 

Always use a good mask, and dust collection, regardless if the wood is spalted or not.  It's just a good practice.  For example, I can turn spalted maple with little to no reaction, regular walnut on the other hand, and I will be sicker than a dog.  Both are great woods for turning dishes as long as you take reasonable precaution.

[Rick A McQuay]

I'm being pedantic but you keep saying mold when I think you mean fungus or fungi. Spalting is caused by fungi, not mold. They are both types of fungi (as in animal, plant, fungi, bacteria, etc.) but are also very different things, just as clams and humans are both animals but very different.

[Hybrid-woodworker]

Personally, I don't make anything "usefull" from spalted wood, in my opinion, there is no need. There are hundreds of figured woods and laminations and on and on, without resorting to spalted wood. I use spalted for art/decorative pieces only. I see lots of spalted cutting boards and spoons for sale in gift shops but I do not want to put my family or my customers at risk. I think it is a personal choice based on your understanding of the risks involved. It is like the rest of woodworking, ask a question of 10 woodworkers and you will get 11 different opinions. :-)

BRuce