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BigTex

Glaze that is not food safe okay on mug handle alone?

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Long time listener, first time caller here. 

I love the Turquoise Matte glaze from Coyote, but it isn't food safe. If I used a food safe glaze on the body of the mug could I still use the matte glaze on the handle or should I keep all glaze on the mug food safe?

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It's fine having glazes which are not food safe on surfaces that don't come in contact with food or your lips. Use a safe liner glaze inside the mug and the top of the outside where the mug touches your lips and then the Turquoise Matte (or any other glaze) on any parts other than those that you like.

Welcome to the forum.

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Thanks, Min. That's what I figured, but wanted to cross-check with the experts here just to be on the safe side. I'll try to remember to post a photo of the results!

 

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just being a devil s advocate here

say a customer has a trace of something acidic on their hands

this leaches some of the poison out of the handles glaze

lets say they are eating a muffin while using your mug

thus they get poisoned by the non food safe glaze

just a little bit

is this still ok to use

consider:

take some time

you may have a lot of it on your hands

if not now then very soon you will

as society shutters completely for many months 

coming soon 

learn how to formulate and mix your own food safe glazes

matt katz online class comes to mind

there are many others 

then you can sleep better at night

so can your customer 

we will survive current virus and financial crises

think long term

lets make the new world a better place

become the best potters we can be

this is not a game of

can I get away with using toxic glazes

or is it

the choice is yours

yes

the choice is yours

 

cheers Mosey

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19 minutes ago, Mosey Potter said:

just being a devil s advocate here

say a customer has a trace of something acidic on their hands

this leaches some of the poison out of the handles glaze

lets say they are eating a muffin while using your mug

thus they get poisoned by the non food safe glaze

just a little bit

is this still ok to use

consider:

take some time

you may have a lot of it on your hands

if not now then very soon you will

as society shutters completely for many months 

coming soon 

learn how to formulate and mix your own food safe glazes

matt katz online class comes to mind

there are many others 

then you can sleep better at night

so can your customer 

we will survive current virus and financial crises

think long term

lets make the new world a better place

become the best potters we can be

this is not a game of

can I get away with using toxic glazes

or is it

the choice is yours

yes

the choice is yours

 

cheers Mosey

I can't think of anything that would be so toxic that you'd get it on your acid covered hands and then transfer it to your food and into your mouth in any amount that would be harmful.  I think the acid on your hands would do a lot more damage.

The worry for me is chronic exposure, so if the inside was glazed with the toxic glaze, a small amount would come out each time it's used and the lead or cadmium or copper etc would build up in your system over a period of time since the body is not great at getting rid of these heavy metals.  A perfect storm of muffin eating while stripping your driveway and drinking coffee isn't really a worry anyone should have.  

To be clear I don't advocate using cadmium or lead in any glaze, especially if it's going to be on a functional item, but if it's just a manganese saturate or non durable glaze, I don't see any harm on putting it on the handle or outside.  

Everyone has their own personal definition of what is dinnerware safe, but the FDA does have a definition.  Here are the dinnerware safe limits on lead: https://www.fda.gov/media/71764/download

 

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Mins response covered it well-food safe on the inside and lip.

I use a white liner and lip on my tourquise galze. The idea is keep the customer away from non food safe surface. As far as hand leaching well thats a long shot-as laim said I was pounding muffins working will driveway asphalt while pouring my lead weight belt lead into lead molds  downwind while licking non food safe outsid of my mug. Well you get it everyones idea of safe is different . The limits that are posted above are the law in guidline form and really it means keep the food surface free of lead and cadmium .If you like to lick coffee drips the outside of your mug well you may have other issues.Was that a gluten free muffin or baked in a rusty pan???

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My view is that only "food safe" (a term which is actually quite fuzzy, but let's not get into that right now) glazes should be used on the entirety of any ware that is intended for functional eating. Both inside and outside surface, handles, etc. should be "food safe." This is not because anybody might be licking the outsides and handles of their coffee mugs - they won't;  but because the notion of "not food safe" is usually synonymous with a less stable glass that might leach a metal oxide colorant. But further, if that glass is not stable and durable, then it probably won't survive repeated trips through the dishwasher (with its highly alkaline detergent) and consequently, the (exterior) surface will begin to degrade and the color leach out into the dish water. Nobody will die from it, but that mug will get ugly fast. Save the non "food safe" glazes for purely decorative work.

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It's interesting to me that Matt Katz is cited. He is definitely one of the best, science based glaze teachers out there right now. He also advocates for accuracy. He was one of the minds behind the test that cast some serious doubts on the idea that germs easily hide in crazing lines and will poison us all. In a small sample study he found that how you washed your dishes had more to do with the bacteria growth than the surface, although the surface did have some effect. He's also the first one to point out that there's typically not enough material in, say, the amount of oribe glaze (soft, copper bearing) to either acutely or long term poison anyone. Hypothetically if there was, you would die from drinking the amount of water you'd need to dissolve it in first. 

In my personal work, I prefer to use glazes that fit the clay body, but that's my own preference. I won't balk at purchasing someone else's work who has something more decorative on the outside though. 

There's this lecture he did for NCECA in 2016, and a few other free videos on his website that talk about this.

 

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1 hour ago, Callie Beller Diesel said:

He was one of the minds behind the test that cast some serious doubts on the idea that germs easily hide in crazing lines and will poison us all. In a small sample study he found that how you washed your dishes had more to do with the bacteria growth than the surface, although the surface did have some effect.

 
Ryan Coppage, PhD along with Ruhan Farsin and Laura Runyen-Janecky, PhD published a similar study.
 
The Scribd article has been deleted but thankfully it's still available: Techno File: Dirty Dishes
 

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