Chromium oxide green at high temp

[Pawelpksa]

Dear, I added 10% of chromium oxide green to white porcelain and want to use it in agateware for firing in cone 6-8. Do you have experience how the green color changes in such scenario? Will the oxide affect white part of the body?

[Babs]

Chromium bit toxic.....I would use a body stain in this situation.l

Does time and deposit on kiln and nearby pots...makes some white glazes turn pink.

[Pawelpksa]

and there wil be no food contact with it

but yes, other pots will be fired the same time

[Pres]

I would really reconsider the use of any chromium in a clay body. The toxicity is high, and absorption through skin is an issue. If you are working with the clay, make certain to wear gloves. As Babs said consider using a body stain, and you will have much more control of color. 

Glazes that contain Tin as an opacifier will flash pink to crimson when in a chromium atmosphere. Something to consider also if your kiln is not vented, and if it is vented. . . to where it is vented.

 

 

best,

Pres 

[Rae Reich]

5 hours ago, Pawelpksa said:

and there wil be no food contact with it

but yes, other pots will be fired the same time

Pres and Babs are not referring to the users of the finished product, but to you and the exposure you have to the oxide while throwing and firing. 

[Pawelpksa]

Yes, I understand. Firing takes place in garage. Throwing is the issue. Thanks all for the wornings, I appreciate much.

Any comments on change in color shade after firing?

[Babs]

throwing wedging trimming dealing with scraps. Dust , fumes from kiln.

Carcinogenic,  really bad news.

I would go with a body stain.

CHROMIUM WILL stay around and in your kiln for a long time pawelpska.

Read up on it , don't Take such personal risks.

[Pawelpksa]

Ok, convinced - thanks for saving my health (serously). Theoretically I know it but often tend to think that practice is different. I have an opportunity to see some old traditional potters who still produce their glazes from lead and copper oxides themselves and use for food crocks. In then wonder - that was practiced for centuries..

We don't have easy access to Maison Stains here, in Poland.  I use mainly Terra-color, but their stains are encapsulated. At the moment I used their pigments. Some of them contain Cd but are declared as encapsulated as well. They are declared as for body clay or glazes.  See here the catalogue.

Now, the QUESTION:

What is more in the stains comparing to simple pigment? Does it preserve color better?

Regards

[Babs]

A question for the company:-)))

We used to have water delivered in lead pipes ad well.

Roofing paints with lead content.

Where lead is processed from the ore it has been found the pop.esp children playing in the dirt of their garden have a much lower functioning capacity in many areas...shows up in schools testing. Thus folk from a town here are nicknamed "lead heads"....

We can learn from history but apparently not in the political arena.

 

[glazenerd]

Paw:

clay is a different beast than glaze: it can take 3-10 times the amount of colorants to replicate a glaze color in clay. Chromium  in clay also has effects on the chemistry other than colorant.  If you are looking for a specific green: try using  small % of copper carb: or you can use copper carb in conjunction with green body stains. Mason makes "body" stains specifically for clay, and general stains for glaze. You need to slurry down premix to a near slip consistency in order to get equal distribution of color. You can wedge stains in, if you are trying to get an agate look. Tough to do, but can be done.

Babs: as an arm chair historian: over half of the potters making pieces during the Roman Empire died before age 30 from lead poisoning.

T

[Babs]

Yeh  but it won' happen to me, right?

Esp now I have passed 30 a couple of times:-))))))

[Rae Reich]

On 9/28/2018 at 5:47 PM, Babs said:

Yeh  but it won' happen to me, right?

Esp now I have passed 30 a couple of times:-))))))

Right! Because you're not using lead and other poisonous elements carelessly.

But, boy, those lead glazes were lovely. And so simple and reliable for centuries that they were still available here through the '80's. Working with high-fire, which burns out lead and makes it useless, has probably saved my generation of potters.

Fortunately, such hazards have now been taken seriously, although it seems that each new generation of potters will have to be re-educated (same situation with Civics).