MElinda Dempsey
from
Ireland
asks
Please could you tell me the percentage of the amount of grog and the size.
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Scarva Replies:
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The PF670 Black Textured clay contains 25% 16-30s Grogg.
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Zsiri
from
Ireland
asks
Hello,
could you tell me the what percentage this clay shrinks please?
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Scarva Replies:
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At 1200°C this clay shrinks 10%.
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Trish
from
United Kingdom
asks
When used with your low expansion white gloss glaze, would this clay and glaze be food safe?
Thank you.
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Scarva Replies:
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No this would still not be suitable for domestic ware, the body is still to open even combined with a suitable glaze the smooth black is also not suitable, black clay bodies are not suitable for domestic ware, sorry about this.
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Josie
from
United Kingdom
asks
Hi, could you tell me the porosity of this clay. Thanks!
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Scarva Replies:
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Determining what the porosity of a clay will be down to what temperature it is fired to, therefore I will not be able to answer but I can tell you how to determine the porosity of a clay simply follow the steps.
Take a piece of clay and fire it to temperature.
Weigh it, place in boiling water and leave to cool.
When cold, remove the piece and wipe of excess water.
Weigh again.
The difference in weight, divided by the original weight, multiplied by 100 is the percentage porosity. An ideal clay has 1-4% porosity.
Hope this helps.
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Sal
from
Ireland
asks
Can this be included in the same kiln firing with other white stoneware items (including those with clear glaze) or would the carbon burning affect the other pieces?
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Scarva Replies:
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Yes this will be fine just need to make sure the pots are not to close.
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Oliver
from
United Kingdom
asks
Would this yield good results if burnished? I'm designing a tower that seems to grow out of bedrock and thought that burnishing might make this interesting. Forgive me if it is a daft question, I'm not hugely experienced and I'm blind too. What sort of colour variation is there when firing? Are there dark greys as well as black.?
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Scarva Replies:
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Yes you could burnish this body. It is quite a uniform black colour however the grog is slightly lighter so there is variation in the body. The higher you fire the more black the clay becomes around 1200oC on the controller gives a good result.
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Tracy
from
United Kingdom
asks
Are there any precautions that should be taken when working with this clay. Like when it’s been fired etc
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Scarva Replies:
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Hi,
There are no particular extra precautions that should be taken. Care should be taken not to generate dust if the clay is allowed to dry out. These black clays contain a small percentage of Manganese Dioxide so I would recommend not eating or drinking when using black clay and washing hands thoroughly when finished. Due to the Manganese content I would avoid using this clay with children.
Hope this helps!
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Kate
from
United Kingdom
asks
Hi there
Please could you tell me which white glaze have you used in the picture of the vase ?
I am going to try this clay with a white zircon glaze and wondered which one you have used.
Thanks
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Scarva Replies:
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Here is a link to the glaze we have used:
https://www.scarva.com/en/Scarva-GZ2161-Low-Expansion-Tin-Gloss-Glaze/m-5170.aspx
Hope this helps.
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Emma
from
United Kingdom
asks
Can you make this clay watertight? Making a case for flowers for example?
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Scarva Replies:
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We have found the black clays especially the PF670 and PF660 even when fired to maturing temperature tend to remain porous if you glaze it will help.
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Marl
from
United Kingdom
asks
What is the potential risk of using this clay for food and drink once fired?
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Scarva Replies:
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We do not recommend this clay for tableware as, due to the open texture of the body, bacteria can be harboured and develop in these areas. Hope this helps!
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Ann
from
United Kingdom
asks
Would your NCS113 Equator glaze work with this clay?
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Scarva Replies:
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Hi, black clays are difficult to achieve good glaze fit with. I would suggest that you avoid using NCS113 with this clay as I don't think it will give great results. Really this clay needs a low expansion glaze such as GZ2170. Hope this helps!
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Rachel
from
United Kingdom
asks
Which glazes would work best with this type of clay then? Would the low shrinkage clays work well?
Many thanks
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Scarva Replies:
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Glazes do not work that well on the black clays as there is so much carbon burning of from the bodies. They tend to bubble, you could try applying decorating slips to get a little colour but obviously your colour palette is limited.
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