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Manganese Dioxide

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HI everyone, Ive been researching lucie rie lately and her glazes. Manganese Dioxide specifically. Apparently Manganese Dioxide is extremely toxic. whoops. handled it without gloves nor a respirator.  I even breathed the fumes from the kiln. Bad mistake. Anyways I applied 100% manganese dioxide onto the exteriors of a few things, the outside of a bowl, outside of a coffee cup, and the very lip of a mug. The Dioxide is extremely thick, no thin coat. Is this dangerous even after firing?  Would be poisoning people with this? Can it leach through a clay body (stoneware)?  Is it still dangerous to have it only on the exterior of things? Thanks!

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Yes, manganese dioxide is toxic -- both in dry form (breathing risk) and in suspended form (it can be absorbed by through the skin, causing neurological problems). And, your kiln should be vented to outside to remove gases emitted during firing. Lip of a mug is not a good idea as the contact is a point for leeching. Outside of a bowl or mug -- to highlight decoration or make a mark, likely okay; to cover the full surface -- not a good idea. A heavy application is going to go metallic and may/may not completely melt. Will it leech through to inside -- depends. Are your firing your stoneware to vitrification? If not, could be problematic. Are you using a durable, trusted liner glaze? You might see some fuming from your wares to others in the kiln -- are you firing your own kiln or are you risking others pottery in a community kiln?

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The Bill Carty talk in Milwaukee last year addressed this. He suggested that the neurological effects are only an issue when exposed to vaporized forms of Manganese (The MSDS information is from the steel industry, where everything they handle is at high heat). Proper materials handling still applies, however the greatest risk is breathing the kiln fumes. Also, be aware that subsequent firings will still give off fumes, as all surfaces in the kiln will hold on to a bit of the Manganese. Be sure to wash all wares prior to use as well to take care of the residue. As for the leaching issue, a properly formed gloss should contain the oxide to a limit.

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From Edouard Bastarache M.D.Occupational & Environmental Medicine:

 

http://digitalfire.com/4sight/hazards/ceramic_hazard_manganese_inorganic_compounds_toxicology_317.html

 

As Colby said Bastarache's research also indicates the fumes from the kiln are the biggest hazard. 

"The inorganic compounds do not penetrate the body via skin like some organic compounds, such as certain
tricarbonyls.
Inhalation of dust or fume is the major route of entry in occupational manganese poisonning. Also inhaled large particles are ingested after mucociliary clearance from the lungs. Gastrointestinal absorption is generally low (5%). Very few poisonings have occured after ingestion."

 

For fired wares testing in a lab is the only way to know how much is leeching. I wouldn't use a mug with a manganese wash on the rim.

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Why use it at all? There are so many glazes, stains, etc, why use something that you know can be toxic to your customers??

 Ok if you want to take the risk, but to subject other people to it?

 

 I know most oxides are dangerous and toxic, make sure your glazes are able to contain the toxicity to use the chemicals. Research and test.

 

 B

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Why use it at all? There are so many glazes, stains, etc, why use something that you know can be toxic to your customers??

 Ok if you want to take the risk, but to subject other people to it?

 

 I know most oxides are dangerous and toxic, make sure your glazes are able to contain the toxicity to use the chemicals. Research and test.

 

 B

 

This is my stance, too. I will not use manganese in any of the glazes in my studio. There are enough good glazes out there that I don't need the risk for me, my students, or my customers.

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My favorite clay is Laguna 403, which is a speckled buff cone 6.  I thought the dark spots were from a form of manganese, but looking at the MSDS for the clay there is no Mn mentioned.  First of all, is this Mn?  And second, would this pose any harm other than fumes during firing?

 

thanks,

Jeff

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Well isn't 112 clay used in many a studio?  And aren't all those specks

(112 BROWN CLAY (Cone 4-6)

Plastic clay for wheel and modeling. The addition of granular manganese gives a speckled surface. )

 

Manganese?  Is this dangerous.  I just started using 112 and there are a lot of specks and I fire in my basement with a window fan.

Am I being stupid??

 

 

I

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Manganese dioxide mixed into glazes is a fine, powdered material that can be more easily inhaled, etc; not the granular chunks in 112 and other clay bodies. Dangerous in 112 -- no; but, if you have sensitivities/allergic reations to certain raw materials, it always makes sense to find out what is in you clay body, glazes, whatever. Recently, Marcia indicated she used a small, minute percentage of barium in a clay body recipe -- to prevent skimming on the surface. Barium, like manganese dioxide, is toxic and most community studios no longer use barium in glazes due to toxicity. That is not to say that, under strict conditions and amounts, some barium is not useful and helpful.

 

You (me and everyone else) just need to take time to learn about the materials we use and act safely. There is too much "folk (mis)knowledge" and misconceptions out there, too; so find good sources. Maybe a New Year's resolution for all of us -- become more curious about what we use in the studio.

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Why use it at all? There are so many glazes, stains, etc, why use something that you know can be toxic to your customers??

 Ok if you want to take the risk, but to subject other people to it?

 

 I know most oxides are dangerous and toxic, make sure your glazes are able to contain the toxicity to use the chemicals. Research and test.

 

 B

 

This is my stance, too. I will not use manganese in any of the glazes in my studio. There are enough good glazes out there that I don't need the risk for me, my students, or my customers.

 

I was never on planning on selling it at all, I used it because of the effects it can produce. 

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Guest JBaymore

The granular manganese added to clay bodies is not JUST about the granular factor.  It is true that in 'bug lumps'... the issue of the available pathways for the material to get into the human body are pretty much nonexistent.

 

However, granular manganese is often packaged with what are called "fines".  Fines are the dust fraction.  That dust is typically not cleaned out from the large pieces when the clay body is mixed up.  So there is very likely a TRACE of very fine MnO2 material in any body containing granular manganese.  That is in the general dust that the body gets into the studio environment.  Likely this is a very low level.

 

The real potential issues are from the FIRING of manganese containing bodies. 

 

Manganese likes to "fume" from high fired wares.  Fumes are typically misunderstood by many potters.  They are not gases..... they are actually very tiny weenie, isty-bitsy dust particles.  So tiny that the molecular vibration of the air molecules will keep those particles suspended in even still air for 24 hours or more.  These escape into the kiln atmosphere.  If that kiln atmosphere escapes into the studio rooms, then some manganese fume is going with it.  THESE particles are highly respirable, and  therefore represent a high toxicity concern.

 

There is an interesting problem hiding here.  Most fuel fired kilns utilize significant draft flow,  and any stuff released into the kilns' atmosphere is typically mostly vented outside the studio spaces.  So manganese fume, if present, would mostly be picked up and vented elsewhere (if the kiln is installed and operated properly).  But electric kilns do not have this large volume draft flow.  And for what type of firing do we typically see granular manganese added to bodies?  Why... electric oxidation firing.... to add interest and variation to the clay body.

 

So the proper venting of electric kilns that are used to fire manganese containing bodies becomes of paramount importance to the POTTER.  If you don't KNOW that the vent system installed on your electric kiln is working WELL...... then you are "playing with fire" (pun intended ;)).

 

The second issue with the firing side of using granular manganese in clay bodies potentially applies to the CONSUMER.

 

Granular chunks of manganese concentrate a lot of the material in one place.  When you then put a glaze OVER this little spot, that MnO2 bleeds into the glaze lying right over it and colors it.  Nice.... great visual texture.  However that large saturation or OVER-saturation of manganese in the glaze at that point likely is at a level that will not hold all of the MnO2 in solution during the cooling phase.  So if you look at those lovely little speckles under a microscope, you'll notice that the surface is often micro-crystalline....with some Mn stained alumino-silicate forming on the surface.  This manganese is NOT bound well into the glaze melt... and can easily leach out.

 

How much this amounts to as a potential toxin for the user of the wares is impossible to predict.  It depends on so many variables and factors.  The particular clay body and how much manganese granules per square inch are on the surface, the nature of the overlying glaze, the thickness of application of that glaze, the firing cone, other colorants present, and so on.  The only way to accurately assess if this is an issue is a routine of sampling of the production and actual lab testing to KNOW the answer.

 

The comment above from bciskepottery about KNOWING your materials is probably the MOST important comment in this thread.  It is very easy to take 2 or 3 pottery classes, buy some equipment, and set up and start making and selling pottery.  It take YEARS of study and experience to actually know what you are doing.  Clay is long.... life is short.

 

best,

 

............................john

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And even if you're not planning on selling it, you may not have control over the pot's entire future. What if it's still around once you are not? Subsequent users will have no clue. I've used this caution many times with students who want to use non-dinnerware safe glaze on the interiors or rims of potentially functional items...

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Hi all, 

I've been using Standard 266 which has manganese dioxide. However, I can't seems to find the limits of safety and what percent of Mn is in this clay. Can anyone help?

I fire in a small community studio in a vented electric kiln. It seems the fumes are the most dangerous. If this is true, would it be wise to choose another clay body? *even though I love the 266 and so do my students!

 

I'm new to posting, so I apologize if this has already been covered in past topics.

Thanks

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In a word, yes.

That said, too much of anything is still bad. It's just that copper reacts in the body differently than manganese. Too much iron is also not good, but all of them have different levels of volatility, solubility, and levels of use in our biochemistry. What's that saying about poison being in the dose? Borax is used as both a flux and in ant killer.

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