Karen and Cliff Sandlin on thu 14 feb 02
Hi John:
I bought your book, but have many questions:
I want to test Glossy Base#2 on Page 96, but want to know what mesh of
silica, what kind of talc, and whether the whiting is also calcium
carbonate 325 mesh? Laguna's catalog lists several choices for these
items and I want to be sure I get the right ones. Could you be more
specific on any ingredients that could have variants from those on page
96?
Also, I am a member of the Clayart list and copied a glaze attributed to
frogpond that was tested by Alisa of Denmark, called Floating Green.
The recipe:
30 Nephelite Syenite - (Laguna lists A270, A400, and minex-7---which one
shall I order?)
21 Gerstely Borate
8 Whiting (325 mesh calcium carbonate?)
10 Kaolin (Laguna catalog gives 7 different types-does it make a
difference which one?)
31 Silica - what mesh?????
Add
2.0 chrome oxide (the green?)
1. Cobalt oxide (the black?)
Also, Alisa tested on white iron-flecked stoneware. Could you tell me
if this has been tested on plain white stoneware and if the effects were
similar?
My last question is that someone told me about a little book that
converts glaze weights to glaze volumes. Do you know of such a book
and, if so, where I might obtain it?
I am a hobby potter working out of my garage and I apologize if there
are some of these questions I should know and don't, but I will be so
appreciative of any help you can give in making my first testings.
Thanks.
Karen Sandlin - sandlink@bellsouth.net
John Hesselberth on thu 14 feb 02
Hi Karen,
I've tried to answer your questions below:
on 2/14/02 10:52 AM, Karen and Cliff Sandlin at sandlink@BELLSOUTH.NET
wrote:
> Hi John:
> I bought your book, but have many questions:
> I want to test Glossy Base#2 on Page 96, but want to know what mesh of
> silica, what kind of talc, and whether the whiting is also calcium
> carbonate 325 mesh? Laguna's catalog lists several choices for these
> items and I want to be sure I get the right ones. Could you be more
> specific on any ingredients that could have variants from those on page
> 96?
I use 325 mesh silica. If you really do a good job of soaking at peak
temperature it probably doesn't make much difference if you use 200 mesh.
The finer mesh just melts a little more quickly. But 325 has always been my
standard. Same with calcium carbonate (whiting)--I use 325 mesh
> Also, I am a member of the Clayart list and copied a glaze attributed to
> frogpond that was tested by Alisa of Denmark, called Floating Green.
> The recipe:
>
> 30 Nephelite Syenite - (Laguna lists A270, A400, and minex-7---which one
> shall I order?)
>
> 21 Gerstely Borate
>
> 8 Whiting (325 mesh calcium carbonate?)
>
> 10 Kaolin (Laguna catalog gives 7 different types-does it make a
> difference which one?)
>
> 31 Silica - what mesh?????
As I mentioned a few weeks ago on Clayart, Floating Green is not my glaze.
I was just documenting the testing that Diane Woloshyn had done of it. She
says she doesn't know the source of the glaze either. I've never tested
that particular one. Again I really doubt that it makes much difference
whether you use 270 or 400 mesh neph sy. I'd buy 270 if I were you. I'm
not personally familiar with minex-7. Normally when a recipe just says
kaolin, EPK is a good choice. It is probably the most commonly used kaolin
in North American. Same answer as above on the silica
> Add
>
> 2.0 chrome oxide (the green?)
Yes. Chromium oxide, more accurately known as chromic oxide and usually
called green chrome oxide in pottery supply catalogs, is the only stable
oxide of chromium.
>
> 1. Cobalt oxide (the black?)
>
>
Yes or you can substitute cobalt carbonate (which is what I use to get
blue). Black cobalt oxide is Co3O4. Cobalt carbonate, CoCO3, is less strong
in coloring capability so you have to use more. The approximate conversion
is that 3% of the carbonate equals 2% of the black cobalt oxide.
>
> Also, Alisa tested on white iron-flecked stoneware. Could you tell me
> if this has been tested on plain white stoneware and if the effects were
> similar?
I don't know.
>
>
>
> My last question is that someone told me about a little book that
> converts glaze weights to glaze volumes. Do you know of such a book
> and, if so, where I might obtain it?
No I don't know of such a book--maybe someone else does--however this would
be a very inaccurate thing to do. Bulk densities of our glaze materials can
vary widely depending on mesh size and the amount of settling or fluffing up
the material has had before it is measured. I strongly recommend you stick
with weighing out your glaze ingredients rather than trying to scoop them
out by volume.
>
>
>
> I am a hobby potter working out of my garage and I apologize if there
> are some of these questions I should know and don't, but I will be so
> appreciative of any help you can give in making my first testings.
> Thanks.
>
> Karen Sandlin - sandlink@bellsouth.net
Good luck on your glaze testing.
Regards,
John
web sites: http://www.masteringglazes.com and http://www.frogpondpottery.com
EMail: john@frogpondpottery.com
"It is, perhaps, still necessary to say that the very best glazes cannot
conceal badly shaped pots..." David Green, Pottery Glazes
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