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EvaV

unglazed stained clay bodies

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Hi everyone, 

Kind of newbie here: I have taken some basic ceramic classes in the past, but now I'm getting back into it (yay). I discovered that I really enjoy working with porcelain, specifically making porcelain jewelry.  

I have a question concerning this matter (sorry if it’s a stupid question – I’m still very much in the learning process)

I want to try and stain porcelain clay bodies (I was thinking about mason stains, though they are quite hard to find here in Belgium). I really like the look of unglazed porcelain, but I was wondering if it’s safe to use the stained porcelain on the skin if it’s unglazed (twice fired (bisque and cone 6), but unglazed). I don’t know whether some of the toxic materials in the stains can transfer to the skin and cause irritation (or other unwanted reactions).

Thank you in advance for clarifying this for me!

Eva

PS: sorry if my English sounds a bit off - I'm not a native speaker. 

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Hi @EvaV

I don't know the answer, but perhaps you could apply a clear glaze to the back of the jewelry, to the side in contact with the skin.

I made some pendants, many years ago, that were not glazed on the back, and they were uncomfortable, so I coated the back with clear nail polish.

And, your English is very good, I understood your question.

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What about using an underglaze, instead of a stain?  If you wanted the color to be more subtle, like a stain, you could thin the underglaze down a bit. 

As @Chilly mentioned, clear glaze might be a good route to take.  You wouldn't need many coats, to make the surface more durable. 

 

 

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hi, eva, welcome to the forum.

look at the website of one of our members who stains clay and creates beautiful work.  her name is Chris Campbell and you can find her in the list of members.  she has not posted much lately but the photos show how much she knows on this subject.   there are previous posts with your exact question as well.

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Stains could be added to the clay body and mixed thoroughly which will require some prep work to minimize the transfer of colorants to all of your working surfaces. Not a big deal, just might want to have cheap/disposable dedicated wedging boards, and working surfaces. Mason stains are essentially encapsulated mixtures of colorants, so they are much safer to handle with your bare skin than raw colorants, however I do not advise spreading them around heedlessly. Likewise, you may not want unintended transfers of colors to other works.

Unless you desire the marbling effect of mixing numerous colorants into your clay body, you may find it easier to apply the stains to the surface of your finished objects. Stains can be mixed 50/50 with frit 3124 and fired to cone 06/04 which will produce durable surfaces which I doubt would have any issues with long term skin contact. The mixtures of stains/frits will settle out very rapidly in a container of water to a very dense cake, which will be a nuisance to re-suspend when needed to apply, so a suspension agent could be added to limit this. As well, it does not have great brushability so agents like CMC gum could be added which will give you an easier time to apply.  

Aside from a pendant worn on the neck, and resting against the chest, I cant think of jewelry objects which regularly are in constant contact with the skin (earrings dangle, broaches/pins are generally on attached to clothes, etc).  So this may not be a big concern in general?

If the frit/stain mixture, or the addition to your clay body still concerns you about contact with human skin, then a sealant could be applied over the finished objects to further protect them. Something as simple as spray on acrylics (come in range of surfaces from matte to high gloss) could do the trick, or an actual glaze, which would be the most durable. You could also dip them in resins, which may provide a different surface than the other two I mentioned.

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I did make coloured porcelain as jewellery years ago.

Initially unglazed I found even with earrings the unglazed porc.  picked up body oils, make up etc and a few people mentioned this to me and so I ended up glazing placing at cool spots , I fired pretty high in those days.

Glazing one side too fiddly for me and suspending on trees at high temp I didnt pursue for long.

Could have made a low fired glaze and put in hot spots in bisque fire I guess.

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45 minutes ago, Babs said:

Initially unglazed I found even with earrings the unglazed porc.  picked up body oils,

Interesting! Were the oils/dirts easily washed away with soap/water, or had they penetrated deeper into the porcelain?

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The solution to the absorption of oils of porcelain jewelry is to burnish the area to be left unglazed, and fire the porcelain until the porcelain is mature! The area can then be polished with fine emery cloth to remove any residual roughness.  The definition of mature is:  zero surface porosity!  

Some potters call this 'vitrified'; others measure water absorption; if the product is expected to resist oil, then measure absorption using oil instead of water.  

LT

 

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+1 for what MMR said.

I made some red clay dishes with a very low absorbency for our home, left part of the clay unglazed on the outside. Before making them I soaked some unglazed test pieces in different liquids to make sure the clay didn't stain. Beet juice, strong tea and canola oil. Left the test pieces in for days then ran them through the dishwasher, zero staining on all the tests. We've been using the dishes for about a year now, daily use, no staining on the unglazed parts. I would expect the same results if porcelain was used.

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