[Clayart] Homemade Cone 5 and 6

Robert Harris robertgharris at gmail.com
Tue Apr 12 16:49:50 UTC 2022


And the frits probably contain Bismuth and/or Zinc for the 022-014 range.
While bismuth trioxide is yellow, the subnitrate is white.
And Digitalfire suggests that Bismuth compositions can have a softening
point as low as 390C/734F.

On Tue, 12 Apr 2022 at 10:37, Robert Harris <robertgharris at gmail.com> wrote:

> I imagine the low cones are mostly fritted.
>
> On Tue, 12 Apr 2022 at 05:13, David Hendley <farmpots at eastex.net> wrote:
>
>>
>> On 4/11/2022 10:07 AM, ronroy at ca.inter.net wrote:
>> > I visited the Orton cone factory way back when. I'm pretty sure they
>> > were using red art clay. You will notice that the lower cones are
>> > redish - like the colour of red art - so there will be iron present to
>> > help melting at lower cones.
>> >
>> > I was asking questions - like how do you get the same result when red
>> > art is so
>> > variable? They told me they made a batch, made some cones and fired
>> > them next to standard cone they had lots of. If the cone did not bend
>> > properly they adjusted the batch and tried again - till the batch was
>> > right.
>> >
>> > If red art is used make sure you get a bag and reserve it for making
>> > cones.
>> >
>> > RR
>> >
>>
>> Yes, I use Redart clay for for my cone 06 cones. Since Orton cones are
>> red in that
>> temperature range I decided to make mine red as well, by using Redart.
>>
>> My formula and recipe is:
>>
>> CaO    .65
>> MgO    .07
>> K2O    .11
>> Na2O  .17
>> Fe2O3  .08
>> B2O3   .72
>> Al2O3  .31
>> SiO2   2.22
>>
>> Redart clay   48.5
>> Custer feldspar  9.0
>> Gerstley borate  28.0
>> whiting  10.5
>> total     96.0
>>
>> I have been using the same batch of Redart (not just for cones) for more
>> than
>> 30 years, since I bought 4 bags in about 1990!
>>
>> So, what ingredients are used for really low temperature cones?
>> When you get down to the luster firing range, cones 018, 019, 020,
>> the cones are white again, as are high fire cones.....
>>
>> David Hendley
>> david at farmpots.com
>> www.farmpots.com
>>
>
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