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Hi all

Cadmium red has a bad reputation- is this justified? Are cadmium glazes as toxic as the media suggests?  I have tried using it in my studio with mixed results- it is a difficult glaze to use- esp. to get a uniform surface on which to work. If anyone out there has a lot of experience with this glaze I would be interested to exchange ideas. I am not long in the game- just 5 years or so, but I love experimenting with my own glazes and techniques and very happy to share ideas.

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Cadmium is pretty bad news.  There are two kinds of hazards a studio potter has to be aware of—poisoning yourself/studio mates and poisoning your consumer.

Studio hazards are many and we work with lots of acutely toxic and chronically toxic substances. Dust control, work wet, etc etc. covers all that.  Cadmium stains are now available encapsulated, which should reduce studio risk.  Talking to your doctor is also a good idea, there are a whole protocol of tests for cadmium levels if you’re concerned.

Cadmium’s real issue comes from the fact that it can poison your end user.  Pretty easily.  That’s what the leaching laws are about.  a poorly formulated cadmium glaze is a lot higher stakes than a poorly formulated copper or cobalt glaze.

Gettig cadmium out of the body is a lot harder than most other metals.  Chelation doesn’t really work.

Not saying don’t use it.  Just be extra safe, and test your stuff if your plan on selling it.

Edited by Tyler Miller

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Hi

Thanks for your reply.

I have only done one firing with cadmium- and I have no intention of using it on tableware!

I have made decorative oil burners, which will in all eventuality never even  get washed, let alone put anywhere near food.

I am completely aware of the hazards, but this ware was used commonly in the 60's and 70's as far as I know. I was interested in getting the real facts about it, not hysterical outbursts with no factual data as reference.

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I hope this helps:

A world health organization report on Cadmium:

http://www.who.int/ifcs/documents/forums/forum5/nmr_cadmium.pdf

A review of lit from PubMed (if behind paywall, use Uni library for access):

https://www.ncbi.nlm.nih.gov/m/pubmed/11904357/

Another review detailing toxic effects with discussion on treatment (excerpt below):

https://www.hindawi.com/journals/tswj/2013/394652/

“There is no agreement in the literature regarding treatment of Cd toxicity. Human studies are few and anecdotal. While clinical protocols exist for the use of EDTA, DMPS, and DMSA [101104], they rely for the most part on clinical experience and on in vitro and animal studies [105106]. EDTA is the agent most widely accepted for clinical use. While it may seem axiomatic that reduction of body Cd burden would decrease its toxic effects, not all authorities agree that active measures beyond avoidance are indicated, at least for acute poisoning, where concern exists that chelation may aggravate damage to the kidney tubules [107108]. For chronic exposures, however, there is considerable evidence of chelation’s clinical efficacy, in humans and in experimental animals. Several chelators have been used. Clinically available c”

 

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I can only give information as far as the EU is concerned, and that may differ from your South African abode. However, general advice is on Page 32 of this randomly selected publication:

Food contact materials – metals and alloys

Proposed future EU limits are given on Page 21/22 here:

FCM MS WG Group Ceramic

I'm not aware of any hysteria in either document, but it could be hiding behind the small print. Both documents are worth reading in full, assuming a general interest in such things.

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4 hours ago, Tyler Miller said:

Cadmium is pretty bad news.  There are two kinds of hazards a studio potter has to be aware of—poisoning yourself/studio mates and poisoning your consumer.

Studio hazards are many and we work with lots of acutely toxic and chronically toxic substances. Dust control, work wet, etc etc. covers all that.  Cadmium stains are now available encapsulated, which should reduce studio risk.  Talking to your doctor is also a good idea, there are a whole protocol of tests for cadmium levels if you’re concerned.

Cadmium’s real issue comes from the fact that it can poison your end user.  Pretty easily.  That’s what the leaching laws are about.  a poorly formulated cadmium glaze is a lot higher stakes than a poorly formulated copper or cobalt glaze.

Gettig cadmium out of the body is a lot harder than most other metals.  Chelation doesn’t really work.

Not saying don’t use it.  Just be extra safe, and test your stuff if your plan on selling it.

Had to read this twice trying to find the hysteria in it. Seems like well-worded and level headed advice to me.

Edited by yappystudent

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Two more links, for Cadmium Oxide and Cadmium  Sulphide,  two forms that are available in the US at a ceramic supplier. 

Well worth reading carefully as the risks to you and those around you are significant. Disposal methods also need careful reading as environmental risks are also significant.

https://www.fishersci.com/shop/msdsproxy?storeId=10652&productName=AC196935000

http://www.dcfinechemicals.com/files2/Hojas de seguridad (EN)/102670-SDS-EN.pdf

 

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Vivk I have some advice for you. 

Anytime as a newbie when you read a reply look at the person’s profile before you reply. Check out other posts they’ve asked/replied.  Esp. When you use such strong language.

Unless you are a troll and planned this...

either way good info here for future readers here.

Did you google this before? Did you notice the EU has been trying to bring legislation to outlaw cadmium? Not sure how that applies to their glaze industry....

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Yeh avoid it. I have a drinking vessel by a Scottish potter , purchased at Harrods, bright red inner, beautiful  unglazed outer.

I don'tdrink from it but I think the comments at the time was that the red had been introduced in an encapsulated form. I'll try to find it.

Edited by Babs

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Thank you Tyler for taking the time to provide these very good references. I will have to study them properly, but that is precisely what I wanted from this forum. Also I am looking for comments from people who have actual experience with cadmium.

Preeta, my country is full of people who make hysterical outbursts- the tweeters and the social media blurters- they cause such damage with their 2-word 1 syllable messages and that is precisely how fake news spreads.  We are in a very volatile atmosphere here in S.A, and I suppose I am being oversensitive to terminology!  So I apologise if my language appeared "strong". It seems that with the advent of the cellphone people are losing the ability to communicate properly, with proper words appropriate to the situation and so much misunderstanding results. This is your old lady talking.

With reference to Tyler's post- I found the phrase  "it can poison your end-user. Pretty easily" quite declarative, if not hysterical. It seems just from the small amt. of reading I have done so far, that there is very little evidence to suggest that. quote "human studies are few and anedotal". But I have some reading to do. 

Also Preeta- it seems that I am unable to read profiles or bios.  Tried to have a look now at Tyler's profile as you suggested but cant access it.

At least the word "hysterical" got me the results I needed.  Lol, Thanks everyone for your input. You can stay irritated with me, thats ok. I can handle it, I live in S. Africa after all. You have to develop a hide  like a rhino here or you dont survive......;)

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VivK,

I realize that strong statements that go against your expected reply, may seem jarring.  Since it seems to be the expectation that Cadmium is fine, I apologize for causing you cognitive dissonance.

My statement was made under the impression that you had begun to research and had maybe poked around the forum to see that acceptable leach limits, potential for leaching, and potential for harm were set a little closer together than for others.

Let’s unpack that declaration (if not hysteration):

Sputty et al. have supplied limits to cadmium consumption (links above)

et al. (me) provided detailed reviews of evidence and cadmium’s toxico kinetics (links above)

and then I posted some studies on leaching a while back that mention cadmium,

like this one:

http://www.mdpi.com/1422-0067/12/4/2336/htm

or this one:

https://www.sciencedirect.com/science/article/pii/S0048969797002441

Taken together, it shows that it’s pretty easy to poison someone (at least chronically), with  poorly formulated cadmium glaze.

 

 

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On 6/18/2018 at 12:52 AM, vivk said:

I live in S. Africa after all. You have to develop a hide  like a rhino here or you dont survive......;)

Ditto here depending on which side of the tracks you live in. Social apartheid is alive and doing well here.  

I am so glad you tried to check Tyler’s profile. Perhaps I should not have assumed you did not. It’s weird you could not see it though. 

The danger of any metal - lead or cadmium is exposure over time - not a one time thing. 

 

 

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Ok so it's a given that Cadmium in the forms discussed above is to be avoided for the end consumers benefit. This is with the understanding that any potter will have safeguards in place to protect their own use of products in their studio, Dry clay being up there as the most likely to be the "straw which breaks the camel's back" and, not ignoring the total life time load, how can this original potter attain a safe, or safer red for the pots requiring a glaze. I think I remember that the pots are oil lamps or the like.

Still pondering how the potter in my reply above had his food/drink receptacles accepted by Harrods....

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16 minutes ago, Babs said:

Still pondering how the potter in my reply above had his food/drink receptacles accepted by Harrods....

Doesnt Gt. Britain have a different policy than we do. dont they accept lead bisilicate glazes too?

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Not a Brit I don'tknow. I guess what I am getting at is there is obviously a safe/safer way of obtaining red, lots of red around.

I happen to think the most dangerous part of any sensible  potter's life is getting into car to deliver pots to places. Statistically way more dangerous......:_////

Used to be the number 17 bus was a higher risk of getting you ...

But the overall load and best practices are not to be ignored.

Hope someone knows a red which helps OP

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7 hours ago, preeta said:

Doesnt Gt. Britain have a different policy than we do. dont they accept lead bisilicate glazes too?

Much of the rest of the world allows lead glazes, both for 'artisanal' and industrial use. Certainly all of Europe. There are limits to be observed, and testing protocols to be followed.

These limits and protocols are under constant revision - see this source I gave above - FCM MS WG Group Ceramic - for details of current proposals and the issues surrounding legislation like this.

6 hours ago, Babs said:

I happen to think the most dangerous part of any sensible  potter's life is getting into car to deliver pots to places. Statistically way more dangerous..

Yep.

Edited by Sputty

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16 hours ago, Babs said:

how can this original potter attain a safe, or safer red for the pots requiring a glaze.

In oxidation an encapsulated stain for a true red or for more of a raspberry red the chrome tin stains or chrome and tin, the latter two requiring a high calcium base. I didn't read the op's post as looking for a safer alternative, but how to use the raw cadmium. 

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A little note on  ceramic history .

Back in the 40/50s they used radioactive material in Fiesta ware dinnerware in the orange color glaze-we later learned it was not good for us humans . When I started my ceramic career  45 years ago lead was the major flux in most low fire glazes-and most house paints-now we know it not good for us. Same deal with cadmium -its in the same category -we know its not good for us.

You can choose to deal with all these materials still but precautions need to be taken. We have learned things as we evolve. Its up to us to use that knowledge wisely .

I have some Pins in my pin collection with cadmium glaze on them from the 70's.They are for wearing on ones clothing.Not a big hazard.

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+1 for what Mark said. Throughout our lives we have to make decisions based on facts or opinions. I think it’s part of human nature to try and find arguments that support our existing beliefs rather than what current research is showing. Education, checking sources and keeping an open mind as to the information being presented combined with the willingness to change our opinion is all necessary, the last being the most difficult to put into practice.

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Very interesting reading. Thanks all for taking the time to add more depth to the discussion.

I have used red glazes and underglazes  (we get AMACO here) but they tend to give a rather dull, flat, opaque finish. (could have been overfired)

What I am trying to get is a nice, vibrant. deep but translucent red which for a red earthenware and a white,stoneware , firing at cone 05 and cone 6 resp. If anyone is prepared to share a recipe and an accompanying image, I would be most grateful!

I suppose I kind of liked the old 60's cadmium reds and oranges-  more for nostalgia than anything, I suppose! There is just something evocative about those glazes- like a red cadillac from the 50's!

 

 

1-Vintage_Fiestaware_Red_Cream_Soup_Bowl_Old_Antique_Fie_005.jpg

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25 minutes ago, Magnolia Mud Research said:

Have you considered using a thin coat of red between two layers of clear? 
The thin red coat over the clear  should be semi-transparent,  and the clear top coat would provide additional visual depth for additional translucent effects. 
  
LT
 

I would bet that the clear layers would just dilute the red layer and ruin the color.

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2 hours ago, vivk said:

Very interesting reading. Thanks all for taking the time to add more depth to the discussion.

I have used red glazes and underglazes  (we get AMACO here) but they tend to give a rather dull, flat, opaque finish. (could have been overfired)

What I am trying to get is a nice, vibrant. deep but translucent red which for a red earthenware and a white,stoneware , firing at cone 05 and cone 6 resp. If anyone is prepared to share a recipe and an accompanying image, I would be most grateful!

I suppose I kind of liked the old 60's cadmium reds and oranges-  more for nostalgia than anything, I suppose! There is just something evocative about those glazes- like a red cadillac from the 50's!

Underglazes, when applied thickly enough to give deep, rich color, are going to be opaque and have no depth. The key then is to apply a thicker glaze layer over them that will supply the desired depth. That's what I do in my work.

Any translucent glaze over red earthenware will be darkened by the color of the clay, and prevent it from being very bright. You either need an opaque glaze or a white clay body.

Generally, a translucent glaze will not be as intense in color as an opaque glaze, however making it opaque can take away some of the visual depth of the glaze. There is a happy medium, though, that can be found by adjusting your opacifiers (tin, zircopax/superpax, etc).

At cone 6 you can do chrome-tin pinks that are a very deep raspberry color. They will not be a true fire engine red, but slightly to the purple side. They can be quite nice. They are opaque, however, due to the tin, and must be applied thickly in order to achieve the best color. Copper reds can be done in oxidation using silicon carbide as a reducing agent. Copper reds are intense deep red (blood red), and have great depth, although more surface variation than the bowl you've posted above. They tend to break white at edges, and can be finicky to fire.

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7 hours ago, Min said:

In oxidation an encapsulated stain for a true red or for more of a raspberry red the chrome tin stains or chrome and tin, the latter two requiring a high calcium base. I didn't read the op's post as looking for a safer alternative, but how to use the raw cadmium. 

The Op didn't ask for a substitute but in the answering "No it's not safe" as all the posters  were concluding,  I went to the next possible stage of trying to help find a solution to the prob.

If a brighter red is required I suggest coating the "to be coloured" area with a white slip , applying the red underglaze then the clear glaze. Much brighter results. Adding orange to yhe raspberry side of red may result in more suitable red?

Yes we learn on our journey with clay. Wish it applied to politics:-/////

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