Sharon Miranda on tue 10 oct 06
Hi all:
I made up a batch (@2,000-3,000 grams) of a glaze i've often used
called Hersch cobalt blue (recipe follows.) For some reason it isn't
working, the glaze comes out a yukky splotchy grey, with a surface
that is not a smooth mat (i spend my life looking for a satin mat
earthenware glaze). Before I ditch this glaze, is there something I
could throw in it to help get it usable?more lithium? -hate to throw
away that much glaze. I don't think more cobalt is the answer here.
Hersch cobalt blue (cone 04-05)
Gerstley B. 315.4
lithium 87
Neph sye 87
EPK 41.5
flint 348.6
whiting 166
add 2 % cobalt carb
And here is another glaze that I found this summer at Haystack. It's a
Lisa Orr glaze called "copper sparkle". I tested it on a white
(earthenware)_ tile (fired to 05), and it is really lovely. Just
exactly copper sparkle. My question is, would this glaze be food safe?
Pemco frit 78
silica 10
lithium 8
EPK 4
bentonite 2
spanish red
iron ox 15
Thanks for any help,
Sharon
Ron Roy on thu 12 oct 06
Hi Sharon,
The first glaze is way short of both alumina and silica so it's not
suitable for contact with food.
I wonder if you have a new batch of Gers Borate?
I think you may have made a mistake in weighing. In that case I will need
more info about how the glaze looks and how it's supposed to look.
You are using cones when you fire - right?
The second glaze - I need to know which Pemco frit?
RR
>I made up a batch (@2,000-3,000 grams) of a glaze i've often used
>called Hersch cobalt blue (recipe follows.) For some reason it isn't
>working, the glaze comes out a yukky splotchy grey, with a surface
>that is not a smooth mat (i spend my life looking for a satin mat
>earthenware glaze). Before I ditch this glaze, is there something I
>could throw in it to help get it usable?more lithium? -hate to throw
>away that much glaze. I don't think more cobalt is the answer here.
>
>Hersch cobalt blue (cone 04-05)
>
>Gerstley B. 315.4
>lithium 87
>Neph sye 87
>EPK 41.5
>flint 348.6
>whiting 166
>
>add 2 % cobalt carb
>
>
>And here is another glaze that I found this summer at Haystack. It's a
>Lisa Orr glaze called "copper sparkle". I tested it on a white
>(earthenware)_ tile (fired to 05), and it is really lovely. Just
>exactly copper sparkle. My question is, would this glaze be food safe?
>
>Pemco frit 78
>silica 10
>lithium 8
>EPK 4
>bentonite 2
>spanish red
>iron ox 15
>Thanks for any help,
>Sharon
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Eleanora Eden on tue 24 oct 06
Hi Sharon,
Put it through insight and compared it to "targets": (If you put the
formulas into a word chart
side by side it might help with seeing it all. That's what I do.)
315.40 Gerstley Borate
87.00 Lithium Carbonate
87.00 Nepheline Syenite
41.50 EP Kaolin
348.60 Flint
166.00 Whiting
2.00 Cobalt Carbonate
0.63* CaO
0.23* Li2O
0.06* MgO
0.01* K2O
0.07* Na2O
0.00* P2O5
0.00 TiO2
0.08 Al2O3
0.22 B2O3
1.44 SiO2
0.00 CoO
0.00 Fe2O3
Cost:
Calculated LOI: 21.37
Imposed LOI:
Si:Al: 17.85
SiB:Al: 20.59
Thermal Expansion: 7.33
Formula Weight: 160.94
now, a ^04 target formula:
Green & Cooper Cone 04
0.11* BaO
0.32* CaO
0.44* MgO
0.13* ZnO
0.32 Al2O3
0.85 B2O3
4.47 SiO2
now, a lower target formula:
Cone 08-05 Leadless Traditional
0.09* BaO
0.54* CaO
0.26* MgO
0.11* ZnO
0.18 Al2O3
1.07 B2O3
3.08 SiO2
Now RR's comment: The first glaze is way short of both alumina and
silica so it's not
suitable for contact with food.
Compare your glaze's % of those to the target and you will see what he means.
If you will send me all the information you have on the frit in the
other glaze I can do the same for it.
Hope you're both doing fine and everything is okay. We will probably
do a test firing on your kiln today.
I will let you know how it goes. We put a layer of kaowool board
under the kiln but that is all we did so far.
I have extra pots for a ^04 firing so it will get put through its paces.
Yesterday I fired my kiln to ^04 and I was getting super low readings
on the bottom and was thinking about
aborting when Fred suggested I pull out the bottom pyrometer a tad.
Jeesch! The reading jumped 300F!
I was touching something. Bless Fred.
Fall fairs went great except for the last one. When I found out what
some other people had done
I didn't feel so bad. Got a CD about selling craftwork. Want a copy?
Send that frit and I will give you the Insight skinny on your sparkle glaze.
xox
E
>Hi all:
>I made up a batch (@2,000-3,000 grams) of a glaze i've often used
>called Hersch cobalt blue (recipe follows.) For some reason it isn't
>working, the glaze comes out a yukky splotchy grey, with a surface
>that is not a smooth mat (i spend my life looking for a satin mat
>earthenware glaze). Before I ditch this glaze, is there something I
>could throw in it to help get it usable?more lithium? -hate to throw
>away that much glaze. I don't think more cobalt is the answer here.
>
>Hersch cobalt blue (cone 04-05)
>
>Gerstley B. 315.4
>lithium 87
>Neph sye 87
>EPK 41.5
>flint 348.6
>whiting 166
>
>add 2 % cobalt carb
>
>
>And here is another glaze that I found this summer at Haystack. It's a
>Lisa Orr glaze called "copper sparkle". I tested it on a white
>(earthenware)_ tile (fired to 05), and it is really lovely. Just
>exactly copper sparkle. My question is, would this glaze be food safe?
>
>Pemco frit 78
>silica 10
>lithium 8
>EPK 4
>bentonite 2
>spanish red
>iron ox 15
>
>
>Thanks for any help,
>Sharon
>
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--
Bellows Falls Vermont
www.eleanoraeden.com
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