Beccap

Right yes - I’m slightly scared of that word zinc chromate - I think that’s where I read it actually was the Hanson page. If you google zinc chromate it says highly toxic and contains the bad version of chrome. But does that apply to pottery? And there is iron in the glaze - can that combine to make iron chromate? Or am I not understanding how that actually works aka overthinking putting ingredients together makes a/b/c…. I did chat more with Linda Bloomfield and she said the base I use is one she uses and it’s a fairly fine one. I source all my materials from bath potters so all ingredients literally just say ‘potash feldspar’ ‘china clay’ etc. Re: cobalt, I have tried it with 1% cobalt and it works so will go back to that.

Oh ive remembered the glaze recipe!

Yes it is a lovely green! I think the feedback is good about using a liner glaze for this one. But relieved to understand that it is the Chromium III that potters use and that isn’t the highly toxic one. Here is also where I read a bit more on the topic https://glazy.org/posts/325743 Would anyone know a situation in which the chrome in the glaze would convert to the more toxic one? I’ve read it can happen in lead glazes but also non lead ones too. I’ve read that’s possible and I suppose that’s why I got scared if zinc changes its colour, maybe it is changing it chemically? I have no idea what zinc chromate is or if it is a thing in pottery or if my glaze would do it but equally wondering if after firing there’s a possibility of the chrome changing. I did message Linda Bloomfield also and her response was that the oxides would be locked in a stable glaze and only amounts above 4% would you begin to question the potential of leaching. It is a recipe that is very similar one she has for a satin matte glaze, and Stephen murfitt has it also. I don’t have the recipe to hand right now. I think the glaze is actually fine. It hadn’t leached and is a satin base I use a lot. But wanting to educate myself as best I can when using these ingredients.

Yes I think when I started using 1% chrome I didn’t realise the dangers associated with it, and then looked it up and read the type that potters use is not the super scary harmful one. My over thinking brain has maybe thought in the presence of zinc, if chrome turns brown - is that chemically altering it to something that is toxic? And I can’t see it because there is also cobalt & rio so the colour change is not there? I think I am possibly overthinking the combination of zinc and the use of chromium oxide….

I’ve read that chrome & zinc can make zinc chromate ? And that’s a carcinogen? Now I’m worried….. does that happen in the kiln? I read the type of chrome potters use the green one, is actually low in toxicity but also may be wrong. What about chrome pink seems to be food safe? I’ve used 2% cobalt oxide. I will try get a picture but it’s just a lovely green….

I started making a new glaze using a Stephen Murfitt satin matt base recipe that contains 3% zinc oxide. I understand zinc oxide is not the problem but that it may contain traces of lead? But not in levels I should be concerned about? That’s at least the conclusion I’ve come to but please correct me. The glaze makes a lovely deep green, but it contains 1% chrome, 2% cobalt, 1% RIO and now I’m worried that it is not food safe? I haven’t experienced any leaching. I’ve read the type of chrome potters use is not toxic and should be ok? But in the presence of zinc is it still ok? And also is 2% cobalt safe? feeling lost and very confused …..

Okay, thank you so much for your responses. I just need to be told how realistic is it for me to be worried. Of course, what I want to do is completely forget about how silly and stupid I have been in the past, and as long as I’m good now - wear masks / mop only / wet clean etc etc then hopefully 2-3 years of bad habits won’t matter in the long run? I definitely feel I’m being neurotic about this but also have been bad and inhaled dust etc GOD what a dumb 25 year old I was! But also needed a reality check about whether I need to be this upset and if I’m good going forward I will be ok!?? If it takes a career of say, mining to develop silicosis - surely that means, as you’ve both said, that I would need to exposed to a LOT of dust for years and years (10?) before it would be an issue? so despite blowing and sanding green ware and brushing a lot and inhaling accidentally dust and coughing…. Eeeek it needs to be much more? im much happier being told I’m being neurotic than if I need to quit pottery because I’ve messed up and risked my lung health!

Thank you so much for you responses! I honestly can’t believe how stupid and careless I was, I just didn’t realise the dangers and never read up on them. I feel my practice has been a dusty reckless one and I just want to know if it’s already too late - I’m now full time in my studio and worried if I continue I’ll make it worse because I’ve already had exposures? Not that I can just stop working of course! It is reassuring to realise the exposure levels of those in the 70s sure, but I’m sure do anxious and wondering if going to a doctor would help. But with no symptoms (apart from anxiety induced ones!) I’m struggling to see why they would do anything. im supposed to be getting married next year and thinking about that, not if I’ll get silicosis in 10 years, I feel I’m being neurotic but it’s hard to know what was too much exposure! for those in class in the 70s, do you know anyone who ever had silicosis?

Having a bit of an anxious time after reading up on silicosis - something I never really considered when I started ceramics 4 years ago (classes for about a year, 3 years working part time / full time) because I associated it with people working in mines or dusty factories and not a little potter in shared studio spaces. I’ve been a full time potter now for 2.5 years. When I started ceramics I wasn’t the best at cleaning up my spaces and used to sweep a lot and accidentally inhale dust. Then I started making my own glazes two years ago - small batches of up to 3KG. Again, didn’t wear a mask and was very very stupid and careless with raw materials. Then last year I found you could use wire wool to dry sand greenware and I would again be very careless, often using it to sand cracks in the surface of slip when my handles of mugs dried out. Basically probably had terrible studio practices for about 2.5 years and for the last 6 months wisened up and now wear a proper mask when making glazes , wet clean everything, never sweep, only mop, never dry sand and only wet sand bisque. I wear a mask now too when fettling glaze after it dries. how much trouble am i in here? It’s taken over my life a little bit and I’m a bit afraid to go back to my studio after Christmas which makes me so sad but also have I messed up? Was my exposure enough to have problems down the line? I can’t believe how stupid I was- I just didn’t realise it was something to concern myself with and now I’m scared I’ve done damage to my lungs?