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Toxic mold in clay?


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Hi! New student here. I was pretty bummed to find out that most clays do have mold in them (not always visible) and that if you have autoimmune issues or mold sensitivity, you should probably give it up. It makes sense that having soggy organic matter sitting in a plastic bag is prime real estate for fungi, as well as covered ware boards and tables that keep getting drenched and aren't fully aired out/ dried out. And my local ceramics studio smelled pretty dang musty the second I stepped in there, even with a mask on. I've been digging through the limited info/posts online about mold and clay and it's a bit complicated because a lot of potters rave about how great mold is for the clay itself, but very little is discussed about whether it's good for the humans using it. I really want to find a way to make these classes work out but also have to be realistic about my limitations. This is supposed to be a relaxing way for me to decompress after all and there's enough to think about it in this world right now! But I am curious to explore the this some more because even a couple of the professional potters I asked about this said they've been wondering this themselves, but it seems there's not much serious, informed discussion around it and there hasn't been much scientific study on it. I know you can take various mold samples and send them to a lab like Mycometrics to find out the species is in your own clay but that requires a level of dedication to science I'm not sure I have in me right now! 

Obviously, mold spores are everywhere and inevitable but need the right conditions to thrive. And it seems to me that pottery definitely provides plenty of opportunities for it to thrive. The thing about mold is that there's SO many kinds, some more harmful than others. And various molds often grow together symbiotically. The toxic variety that you definitely don't want anywhere near you or your house like Stachybotrys and Chaetomium LOVES paper and drywall. Obviously, paper clay is a no no for me. But I'm wondering if there's cross contamination between paper clay and other clays in the warehouse and stores that mix their own clays.

I've considered making my own clay in small batches but then that exposes you to a lot more silica than buying bagged. I don't wanna work with clay that's had bleach added to it, but I'm wondering how much hydrogen peroxide I can add to a batch to be effective but not compromise the clay. 

And inevitably, there are gonna be people that poo poo it and say mold is fine and to relax, but it's not a very helpful blanket statement. Every body is different and every mold is different and every dose is different. Anyway, I'm just curious to hear how you all handle mold in your materials and general work, if you have autoimmune conditions or asthma/respiratory issues, if you personally have mold issues in your house and/or studio, any anecdotal information that might be helpful. I've also heard of a few students having to leave the classes b/c they couldn't physically handle all the mold. 

And some backstory, I've had to deal with toxic mold before (not gonna lie, it was a traumatic experience and a big financial blow) so needless to say, I'm a little cautious around this stuff! Ok, thanks for your time! 

 

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14 minutes ago, Evvie said:

I'm just curious to hear how you all handle mold in your materials and general work, if you have autoimmune conditions or asthma/respiratory issues, if you personally have mold issues in your house and/or studio, any anecdotal information that might be helpful. I've also heard of a few students having to leave the classes b/c they couldn't physically handle all the mold. 

 

Since mold is everywhere and I mean everywhere I try and minimize where it can grow. So moisture, temperature and available food source because I feel I can never make it go away completely.  Peroxide seemed to be something that could provide a relatively benign method of keeping the spores in check since it ends up as water. Bleach can be an irritant in itself for many. So for me a person without any special sensitivity cleanliness and good practice gives me reasonable confidence. I don’t have any bags of moldy clay (at least visually) and if I did I would treat the mold or discard the clay carefully minimizing spreading the spores.

In a classroom environment I think I would do a mold count and yes determine the type, especially if I had folks say they were being affected by it.

Edited by Bill Kielb
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In my experience, very few people are affected by the molds in clay. I've spent 8 years in University studios, 3 years in a clay supplier business, and 17 years teaching classes in my own studio, and I've only run into two people that had to drop classes due to mold sensitivity. I've got students with immune deficiency conditions (I don't know the specific conditions) and it doesn't affect them. Mold is unavoidable in the clay itself, short of mixing your own clay every time you go to work with it, which would be very poor clay to work with. And doesn't seem to be the type of mold that causes strong reactions and health issues like you'd get in moldy drywall. If it was we'd all be experiencing health issues every time we opened a bag. I think that testing a bag of clay for specific molds would be useless because the clay body materials are sourced form different places and you would/could get different spores from every batch of raw materials.

The studio itself is a different story. There's no reason it should be any more moldy than any other environment due to the clay itself. If your local studio is musty, I'd first determine if the issue is the clay, or something else like a damp basement, etc. Just using clay in a space shouldn't contribute to the mustiness if the space is dry in the first place, because the mold needs moisture to proliferate. If the smell is from slop buckets or standing water in the sink, those issue can be easily dealt with. However I've got open slop buckets in my studio, and we do not have any oder or mustiness problems from them. If we did, then lids would solve the problem there. 

Personally, I'm allergic to molds in the environment, and my allergies are always a mess in the Spring when it's rainy and in the Fall from leaf molds. The studio environment never sets them off, though.

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I'm reminded of a tale told to me by a hunter/potter down in Georgia years ago when the conversation of mold came up. He said he had a bird dog that got hurt ran into a pig. on a hunt, and they couldn't find her for a couple of days. Finally found her part buried in a red clay bank along the river. She was doing fine, and the clay and mold had helped her survive. Don't know, but I have heard often that hurt animals will go to water for the water, and the clay.

 

best,

Pres

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I have one mentor who gave up clay years ago because he thought he had environmental allergies to the mould in clay. He found out 20 years later it was something else entirely unrelated, but he’d moved on to metalwork instead by then. His wife has been a full time production potter the whole time with no ill effects.

In 25 years, I have never heard of any of the toxic moulds that are associated with causing major illness growing in clay. (With the caveat that I haven’t heard of everything.) Any information that I can find seems to indicate that whatever microbes grow in clay may irritate sensitive individuals, but otherwise healthy folks should be fine.  People with compromised immune systems, allergies, those on sensitizing prescriptions, the elderly or infants may be affected. I cannot find any indication of a recorded report of a Stachybotrys infection related to pottery clay or even paper clay. Given that it has been a concern for a couple of decades now, enough people have been watching for such things that something should have cropped up by now. Any of the articles that focused on the science of clay and bacteria growth seemed either focused on certain antimicrobial properties of bentonite, or how to fix glaze rheology when your CMC gum has gone wrong.

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I've never had mold issues with clay, it's more bacteria than mold.  Anaerobic bacteria sets up shop in my throwing water and reeks to high heaven.

You'll have to just give it a try and find out how sensitive you are to whatever mold or bacteria is in your studio.  You can't get around it by spraying everything with h2o2, it's just not feasible.

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My wife is very sensitive to mold and I have a studio in our bathroom. It's not the clay, it's your local studio. I NEVER smell mold in my studio space, except sometimes when I first open a bag of clay. Cheese never bothers me either. Like Liam, I get a little anaerobic bacteria from the iron in our well water and that's the worst offender.

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I have Multiple Sclerosis and have problems with some type of molds.   I nearly passed out in a hotel lobby because they had soaked a couch with cleaning solution and it was developing mold on the inside.  They told me I was the second person that morning that was having trouble breathing in that area,  they had the couch removed.   I have never had any problems  with the little bits of mold in my clay.  I pour bleach in my settling water if it starts to stink,  it will only start to smell if something like paint gets into the water.  I have a very dry studio so there is no musty smell in it.    Denice

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There's a phrase that pops up frequently on the forums, with regard to glazing and other "will this work' questions:  "Test, test, test".

If you have a known sensitivity to specific types of mold, you could have your clay - and maybe the air and surfaces in your studio - tested to see what is there.  Then, once you know what you are (or are not) dealing with, you can make better decisions about how to proceed.

As Neil suggested - a 'musty' smell in the studio is more likely to be due to moisture problems in the room/building than from the clay itself.  As clay dries it release a lot of water into the air.  If the space is tightly sealed and/or has concrete walls or floors that are cooler than the air, that water will condense on those surfaces - creating a perfect environment for mildew and other fungi to thrive.  The solution could be as simple as a thorough cleaning - and installing a good de-humidifier.

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I have asthma and react badly to mold. I notice that clay mold doesn’t seem to affect me though except in one weird way.

Recently I found mold in a bag I was reluctant to throw away, and did not want to rework it all with bleach or vinegar. I decided to wedge it up and use it anyway. I found that my hands itched as soon as I start wedging it!  Gloves solved the problem and as I was making a large slab built piece, that was fine. The interesting bit is that I instantly know when a bit of that clay is amongst other reclaim - my palms itch. 

It must be a different strain because I have never reacted to any mold in my clay before. I do try to be careful due to asthma but perhaps have become more complacent over the years. 

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violette,  is the studio you find uncomfortable one where people keep their pieces wet for a long time?   is the throwing water kept for days?  are there barrels of water for reclaiming studio clay?   is the humidity level high all the time?

in your own studio you can be a rebel.   work as dry as possible, keeping the place clean and dry.   there is no reason a modern studio should resemble something from the middle ages.  i remember walking into one in brooklyn.   the floor was covered with 4 inches of clay dust.   i left in a few minutes, sure i would have an asthma attack if i did not leave. 

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  • 4 weeks later...

I have green mold (Pretty sure it’s mold) growing In my white slip.  Has anyone tried freezing slip until needed? I don’t think freezing hurts clay, so would be fine for slip.  Alternatively, would peroxide or an oxiclean product change the chemical composition and ruin the slip?

p.s. for those of you with stinky bacteria in your waste water, oxyclean works great.

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1 hour ago, carissman said:

Alternatively, would peroxide or an oxiclean product change the chemical composition and ruin the slip?

Peroxide ends up as water so it could thin the slip. If I google oxiclean the ingredients appear to be sodium percarbonate, sodium carbonate, surfactants (detergent)  .... polymer ...... water etc.... which decomposes to water and soda ash

So the oxiclean could change things a bit. Probably ends up to be more about proportions.

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Straight drugstore peroxide is usually sufficient. Or my grocery store sells a peroxide bleach in the laundry section that doesn’t have the washing soda or other stuff. (Superstore Green bleach for the Canadians.)

The green stuff in your bucket is just character. Unless you have specific allergies. That one needs oxygen I believe, so you can also just skim it off the top and discard it.

Freezing reclaim slop or attaching slip won’t present any issues. Not sure if it would affect casting slip.

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Freezing slip will cause water to leave parts of the slip, leaving drier clumps when thawed, but a little bit of time in a blender or magic bullet or whatever will set it straight.

If it's casting slip, the water will separate and the deflocculant and other salts present (I'm looking at you neph sy) will crystallize.  Would be a bit more of a task to thaw out casting slip.

What will work fine at keeping mold out though, is a tiny pinch of copper carbonate.

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