Jump to content
Sign in to follow this  
kenk

Porcelain

Recommended Posts

Can I play too?  I'd like a cone 6 translucent body with 12% shrinkage. 

So far NZ kaolin, silica, neph sy, and vee gum t  are the whitest/most translucent, but about 18% shrinkage.  Using POE, instead 0f Vee Gum T reduced shrinkage, and cost.

Adding about to a fifty fifty mix of the above two a third of a body based on EPK, #6, Champion Ball Clay, neph sy, silica, and bentolite L yields a much lower shrinkage, and better feel.

 

 

 

 

Share this post


Link to post
Share on other sites

Your basic formula for a cone 10 porcelain is:

  • 25% Feldspar
  • 25% Silica
  • 50% Koalin

Whiteness will be determined to a good degree by which kaolin you use. Grolleg would be great, but you can achieve translucency with domestic kaolins as well. The big issue with casting the recipe above is that it has very low dry strength to start with, and casting makes that worse. So you may want to substitute some ball clay for part of the kaolin. Be very careful with casting slip recipes, as the low clay content of porcelain requires a lot less water than stoneware bodies. Don't add your water/deflocculant mixture all at once.

Share this post


Link to post
Share on other sites

Just in case you haven't come across them already there are 4 high fire casting porcelain recipes plus 1 for mid-fire in here. Also some throwing porcelain bodies. Be interesting to see some of those recipes made up with NZ halloysite and compare the differences in translucency and whiteness to grolleg and domestic kaolin bodies. 

Share this post


Link to post
Share on other sites

Translucency in porcelain is the result of glass content and molar content of titanium. Kaolin are naturally low in iron and magnesium, but higher in titanium. Once you cross the 0.50% molar content of titanium; translucency begins to diminish. Once you cross 0.90% of Ti02, fired whiteness likewise begins to diminish. To achieve higher glass content.; then at minimum the body requires an additional ten percent  flux content. At cone temps below 7; frit can be substituted to increase glass content as well. When the cone drops down to the 04 range, as much as 1/3 of the recipe can be frit. Although still classified as porcelain if the primary clay is kaolin: in reality the recipe has crossed into the frit ware arena.

If you want to understand plasticity: read "Cation Exchange" in the jan. 2018 Ceramics Monthly. There are traditional and non-traditional ways of achieving plasticity.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×

Important Information

By using this site, you agree to our Terms of Use.