Malone & Dean McRaine on sun 12 mar 00
Hi, I Have regularly used the following glaze for years, raw glazing on
porcelain (Dave's from Laguna) with good results though it is somewhat
prone to minor crawling if there is any break in the surface of the glaze
after application.
Cobalt Green ^10 Ox/Red
Nepheline syenite 70
Petalite 15
Whiting 5
Gerstley borate 2
Ball clay 8
Cobalt carbonate 1
Rutile 2
Bentonite 2
Now I've started experimenting with stoneware (Amador and WS-10 from
Laguna) and crawling is too weak a word for the horrible monstrosities that
have been coming out of my kiln. The small tests I did looked good so I
fired some bigger pieces. Several pieces have bare clay areas measurable in
inches. In some cases the glaze has flaked off the pots and fallen on
adjacent pieces. No problems were obvious when the pots went in the kiln
but it seems that the glaze isn't sticking very well and is getting
loosened in the early stages of firing. I've never used gum to help glaze
adherence but that seems like a possible solution. What's the procedure and
quantities for using CMC Gum or is there another alternative?
Thanks,
Dean
Cantello Studios on mon 13 mar 00
Try adding 2 percent Brown Sugar It will help keep the glaze hold together.
This glaze is very high is soda with 70 of Nepheline Syenite Gum may help to
but try brown sugar first. Chris
-----Original Message-----
From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.UKY.EDU]On Behalf
Of Malone & Dean McRaine
Sent: Sunday, March 12, 2000 5:41 PM
To: CLAYART@LSV.UKY.EDU
Subject: Crawling from hell
----------------------------Original message----------------------------
Hi, I Have regularly used the following glaze for years, raw glazing on
porcelain (Dave's from Laguna) with good results though it is somewhat
prone to minor crawling if there is any break in the surface of the glaze
after application.
Cobalt Green ^10 Ox/Red
Nepheline syenite 70
Petalite 15
Whiting 5
Gerstley borate 2
Ball clay 8
Cobalt carbonate 1
Rutile 2
Bentonite 2
Now I've started experimenting with stoneware (Amador and WS-10 from
Laguna) and crawling is too weak a word for the horrible monstrosities that
have been coming out of my kiln. The small tests I did looked good so I
fired some bigger pieces. Several pieces have bare clay areas measurable in
inches. In some cases the glaze has flaked off the pots and fallen on
adjacent pieces. No problems were obvious when the pots went in the kiln
but it seems that the glaze isn't sticking very well and is getting
loosened in the early stages of firing. I've never used gum to help glaze
adherence but that seems like a possible solution. What's the procedure and
quantities for using CMC Gum or is there another alternative?
Thanks,
Dean
Michael on tue 14 mar 00
Dean,
I use Vgum and Cmc with glazes that I must apply thickly that I do not want
to blow off during firing, while mixing rapidly I add about a teaspoon of
each per liter. You could likely skip the ball clay and bentonite if you
use the binders above.
Just casually and ignorantly looking at your glaze it seems to have a huge
amount of alumina in it and I wonder if this is not causing a problem after
it melts - so much surface tension it pulls up at the slightest
provocation.... like a crack or tiny peeling at drying or dusty bisque
causing poor adhesion.
Michael
At 08:40 PM 03/12/2000 EST, you wrote:
>----------------------------Original message----------------------------
>Hi, I Have regularly used the following glaze for years, raw glazing on
>porcelain (Dave's from Laguna) with good results though it is somewhat
>prone to minor crawling if there is any break in the surface of the glaze
>after application.
>
>Cobalt Green ^10 Ox/Red
>
>Nepheline syenite 70
>Petalite 15
>Whiting 5
>Gerstley borate 2
>Ball clay 8
>Cobalt carbonate 1
>Rutile 2
>Bentonite 2
>
>Now I've started experimenting with stoneware (Amador and WS-10 from
>Laguna) and crawling is too weak a word for the horrible monstrosities that
>have been coming out of my kiln. The small tests I did looked good so I
>fired some bigger pieces. Several pieces have bare clay areas measurable in
>inches. In some cases the glaze has flaked off the pots and fallen on
>adjacent pieces. No problems were obvious when the pots went in the kiln
>but it seems that the glaze isn't sticking very well and is getting
>loosened in the early stages of firing. I've never used gum to help glaze
>adherence but that seems like a possible solution. What's the procedure and
>quantities for using CMC Gum or is there another alternative?
>
>Thanks,
>Dean
>
Ron Roy on wed 15 mar 00
Hi Dean,
The problem is all that Neph Sy - I tried to sub in some spar to fix it but
could not get much in and keep it matte. Here are some minor changes that
may help - test it first but it should look the same. It has a lot of
alumina and alkalies - just like the shino glazes.
If I used hydrated alumina I could do a lot better - let me know if you
want to try that if this is one won't work.
Nepheline syenite - 64.5
G200 - 5.0
Petalite - 14.5
Whiting - 5
Frit 3134 - 2.5
Ball clay - 8.5 (I calculated with OM4 but it will work fine with what ever
you are using.
Cobalt carbonate - 1
Rutile - 2
Bentonite - 2
Total 105.0
Oops - just had another brainwave - try this.
Nepheline syenite - 52.5
G200 - 18.5
Petalite - 14.5
Whiting - 5
Frit 3134 - 2.5
Ball clay - 3.0
EPK - 4.0
Cobalt carbonate - 1
Rutile - 2
Bentonite - 2
Total 105.0
RR
>----------------------------Original message----------------------------
>Hi, I Have regularly used the following glaze for years, raw glazing on
>porcelain (Dave's from Laguna) with good results though it is somewhat
>prone to minor crawling if there is any break in the surface of the glaze
>after application.
>
>Cobalt Green ^10 Ox/Red
>
>Nepheline syenite 70
>Petalite 15
>Whiting 5
>Gerstley borate 2
>Ball clay 8
>Cobalt carbonate 1
>Rutile 2
>Bentonite 2
>
>Now I've started experimenting with stoneware (Amador and WS-10 from
>Laguna) and crawling is too weak a word for the horrible monstrosities that
>have been coming out of my kiln. The small tests I did looked good so I
>fired some bigger pieces. Several pieces have bare clay areas measurable in
>inches. In some cases the glaze has flaked off the pots and fallen on
>adjacent pieces. No problems were obvious when the pots went in the kiln
>but it seems that the glaze isn't sticking very well and is getting
>loosened in the early stages of firing. I've never used gum to help glaze
>adherence but that seems like a possible solution. What's the procedure and
>quantities for using CMC Gum or is there another alternative?
Ron Roy
93 Pegasus Trail
Scarborough
Ontario, Canada
M1G 3N8
Evenings 416-439-2621
Fax 416-438-7849
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