Richard Aerni on tue 31 aug 04
Hello group,
I have two different batches of strontium carbonate, bought from the same
supplier five years apart. The first (oldest) batch is extremely coarse
and grainy, and the graininess does not disappear in the fired glaze. It
wasn't until I ordered another batch of the material years later that I
realized it came in a much finer mesh size, which melts easily into the
glaze. So, I would guess that you have some of the coarser stuff. I would
definitely recommend using the finer grade material, as my glazes which
contain it have improved appreciably with it's addition.
Richard Aerni
On Tue, 31 Aug 2004 07:34:28 -0700, Mary K
wrote:
>Dear John,
>
>I would love to know what the graininess is in that recipe (Cream Breaking
Red).....
>John Hesselberth wrote:
>Hi Gaye,
>
>I would say you got a bad batch, a cheaper/coarser grade, or a
>different material was accidentally substituted when your supplier was
>weighing it out. My strontium carbonate has just a hint of graininess
>when I rub it between my fingers, but it very quickly and easily
>becomes a very fine powder. It disperses easily in glaze suspensions
>and I have never encountered strontium grains in a fired glaze.
Ron Roy on thu 2 sep 04
I have seen this happen many times - especially with Lithium Carb. Supplier
orders a material but does not specify the mesh size. Their supplier has to
either guess what is wanted or just assumes it's what is usually wanted
from another customer or maybe even assumes it does not matter what mesh
size or grade.
We (potters) are not usually the primary customer of materials - our orders
are small compared to industry so we have to be extra careful when ordering
if we want to get them the way we want them.
We usually want our glaze materials to be about 200 mesh - the finer the
mesh size the faster a material will enter fusion.
In the case of silica this works against us - the silica we get now usually
has a lot (like 95%) micron size material - which easily converts to
cristobalite at the higher temperatures - unless clay bodies are formulated
to take this into account. For an excellent article on the subject see
Peter Sohngens article in Studio Potter magazine Vol. 28 #1
RR
>Hello group,
>I have two different batches of strontium carbonate, bought from the same
>supplier five years apart. The first (oldest) batch is extremely coarse
>and grainy, and the graininess does not disappear in the fired glaze. It
>wasn't until I ordered another batch of the material years later that I
>realized it came in a much finer mesh size, which melts easily into the
>glaze. So, I would guess that you have some of the coarser stuff. I would
>definitely recommend using the finer grade material, as my glazes which
>contain it have improved appreciably with it's addition.
>Richard Aerni
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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