Judy Musicant on thu 8 aug 02
Marianne,
Thanks for the kind words. If you try the glazes on the mug and bowl (the Val Cushing satin matte), please be aware of the following. That glaze is gorgeous when it works. However it has a very narrow firing range, and if it's fired a little too thick, and/or a little too hot, it will run off the pot. So, I now use it only on the insides of pots and on the rim. In fact, I tend to use the version with the iron in it on the rims of most of my pots - such as on the tall pitcher with the kinked handle in the Bailey book. It seems to be a durable glaze, as I've done the vinegar test, the freeze and boil test, and the dishwasher test, and it's stood up to all. I should probably do a Currie grid to see if I can get the same effect without the difficulty. If Ian or Ron R. or any of the other glaze gurus want to take a stab it a re-formulation, I'd love their opinions. The recipe is:
Neph Sy 40
Gerstley Borate 10
Whiting 10
Lithium Carb 6
EP Kaolin 12
Silica 12
Titanium Diox. 6
______________________________________________
Light Green - 1-2% Copper Carb.
Light Blue/Green - 1% Cobalt Carb.
Rusty Bronze - 2-3% Red Iron Oxide
Ron Roy on mon 12 aug 02
Hi Judy,
I just started to work on this but - the total is only 96 for the recipe -
if that is correct let me know - if not send me the corrected recipe and I
will do some revisions to cut down the Neph Sy and eliminate the GB - and
add more clay to make it behave better in the bucket.
Let me know which spar you have - G200 or Custer?
RR
>Thanks for the kind words. If you try the glazes on the mug and bowl (the
>Val Cushing satin matte), please be aware of the following. That glaze is
>gorgeous when it works. However it has a very narrow firing range, and if
>it's fired a little too thick, and/or a little too hot, it will run off
>the pot. So, I now use it only on the insides of pots and on the rim. In
>fact, I tend to use the version with the iron in it on the rims of most of
>my pots - such as on the tall pitcher with the kinked handle in the Bailey
>book. It seems to be a durable glaze, as I've done the vinegar test, the
>freeze and boil test, and the dishwasher test, and it's stood up to all.
>I should probably do a Currie grid to see if I can get the same effect
>without the difficulty. If Ian or Ron R. or any of the other glaze gurus
>want to take a stab it a re-formulation, I'd love their opinions. The
>recipe is:
>
>Neph Sy 40
>
>Gerstley Borate 10
>
>Whiting 10
>
>Lithium Carb 6
>
>EP Kaolin 12
>
>Silica 12
>
>Titanium Diox. 6
>
>______________________________________________
>
>
>
>
>
>Light Green - 1-2% Copper Carb.
>
>Light Blue/Green - 1% Cobalt Carb.
>
>Rusty Bronze - 2-3% Red Iron Oxide
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Judy Musicant on tue 13 aug 02
Hi Ron,
Thanks so much for looking at this glaze. Yes, the numbers are those which are published in the Alfred Clay and Glaze book as the revised recipe for this glaze. The original recipe published there showed 12% titanium instead of 6 (I realize this adds up to 102, but there you go); however, this produced an extremely dry and unpleasant texture. BTW, the glaze behaves fine in the bucket - goes on very smoothly. It's just that it's extremely sensitive to thickness and temperature in the firing. A little too thin, and it looks awful. A little too thick and hot and it runs off the pot, but if you fire it a bit cooler, it looks underfired. Obviously, it has a very narrow firing range for optimal results. I've found that if the thickness is just right, and you give it one good coat on the outside, it might not run. It sounds like your Waterfall Brown - gorgeous, but difficult to get just right. That's why I've given up on using it on the outsides of pots.
I have both G-200 and Custer.
Thanks again for your insights.
Judy
Neph Sy 40
>
>Gerstley Borate 10
>
>Whiting 10
>
>Lithium Carb 6
>
>EP Kaolin 12
>
>Silica 12
>
>Titanium Diox. 6
>
>______________________________________________
>
>Light Green - 1-2% Copper Carb.
>
>Light Blue/Green - 1% Cobalt Carb.
>
>Rusty Bronze - 2-3% Red Iron Oxide
I
Ron Roy on thu 15 aug 02
Hi Judy,
First of all I don't think this is a stable glaze - it does not have enough
silica and it is high in alkalies - the sodium, potassium and lithium total
.49 in the Seger formula - that means this glaze is probably leaching
lithium into food. If you want to find that out for sure you will have to
have it tested.
The second point is the amount of lithium - some times glazes with this
amount of lith carb have strange fit problems on certain clays - crazing
and shivering at the same time. I assume you have tested it for fit
problems on the clay you are using.
I don't have a lot of experience with cone 6 glazes - John did most of the
glaze work for our book. Perhaps you should ask him if he has any ideas.
john@frogpondpottery.com
My inclination would be to run the lithium down in a line blend taking out
0.5 lithium each time - 5.5, 5, 4.5, and 4 to see if that was any help. I
don't see much hope because of the way you describe what is happening. Even
with only 4 lithium the SiO2 is barely enough to expect stability.
I suspect you like this glaze because of it's basic instability - so many
of this type are like that and any changes tend to make them loose their
charm.
Perhaps John will have had some experience with this kind of glaze and he
can be of more help than I have been.
RR
>Thanks so much for looking at this glaze. Yes, the numbers are those
>which are published in the Alfred Clay and Glaze book as the revised
>recipe for this glaze. The original recipe published there showed 12%
>titanium instead of 6 (I realize this adds up to 102, but there you go);
>however, this produced an extremely dry and unpleasant texture. BTW, the
>glaze behaves fine in the bucket - goes on very smoothly. It's just that
>it's extremely sensitive to thickness and temperature in the firing. A
>little too thin, and it looks awful. A little too thick and hot and it
>runs off the pot, but if you fire it a bit cooler, it looks underfired.
>Obviously, it has a very narrow firing range for optimal results. I've
>found that if the thickness is just right, and you give it one good coat
>on the outside, it might not run. It sounds like your Waterfall Brown -
>gorgeous, but difficult to get just right. That's why I've given up on
>using it on the outsides of pots.
>
>I have both G-200 and Custer.
>
>Thanks again for your insights.
>
>Judy
>
>Neph Sy 40
>>
>>Gerstley Borate 10
>>
>>Whiting 10
>>
>>Lithium Carb 6
>>
>>EP Kaolin 12
>>
>>Silica 12
>>
>>Titanium Diox. 6
>>
>>______________________________________________
>>
>>Light Green - 1-2% Copper Carb.
>>
>>Light Blue/Green - 1% Cobalt Carb.
>>
>>Rusty Bronze - 2-3% Red Iron Oxide
com.
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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