Trish Messenger on sat 27 mar 04
Hello Everyone,
I could really benefit from some suggestions on how to save my 30
gallons of glaze. I have been doing a lot of research on clayart and in
all of my pottery books but it doesn't look good...
I am using 2 types of low fire earthenware clay with silica sand and
some grog, white and terracotta. I bisque at cone 04 for the white and
05 for the red, oxidation in an electric kiln. I glaze at 06.
What I have come to understand is that the primary cause of glaze
flaking is due to too high of a clay content in the glaze and it is
recommended that you substitute half of the kaolin for calcined kaolin,
taking into account the loss of weight. I am certain that this is the
main cause of my problem but none of my books specify what % of
clay is too high. Is it 15%,20%, 30%?
Another factor may be whether or not you have hard water. I know
that ours is slightly hard and my terracotta pots have scumming. Does
using distilled water make any difference concerning glaze flaking?
I use an alkaline base glaze recipe and adding oxides from there.
100 gr.
Gerstley Borate- 25.8
Ferro Frit 3269- 41.6
Epk Kaolin - 32.6
V gum T- 1 tsp.
Surprisingly, I can still buy gerstley from Sheffield Pottery in Mass.
After every bisque, I rince off the pots in the sink and wait for them to
dry before glazing. This glaze needs to be dipped rather thick in order
for it to look "right". I get these fantastic star patterns in the glaze.
Earlier, I had problems with my glaze not drying on the pots. I would
have to wait 24 hours for 1 coat of glaze to dry! So, I added 2% epsom
salt solution to the glaze and that has helped with the drying. Now, I
can dip my second coat in about 3 minutes but it still takes hours for
the glaze to dry completely.
I have tried applying the glaze thinner and found that it does not flake
off of the bisque but it's too thin. I have also dampened the pots
before dipping and it flakes. I have not rinced the bisque and it flakes.
And I have brushed on the glaze and it still flakes. I should also
mention that my glaze (or clay) has a lot of pinholes not just on the foot
of the pot where I trim. My only solution now is to reglaze and refire,
but this is becoming too time consuming and too expensive. Is there
any hope of saving these glazes or do I have to start over with new
batches using calcined kaolin?
Patiently waiting for responses or a high fire kiln and stoneware.
Trish
Ron Roy on mon 29 mar 04
Hi Trish,
For one thing - adding Epsom salts is exactly the wrong thing to add - it
focculates a glaze - which means you need more water - which increases the
shrinkage - which is one reason your glaze is cracking during drying.
Send me your current recipe and I will see if I can make some beneficial
changes.
RR
> I could really benefit from some suggestions on how to save my 30
>gallons of glaze. I have been doing a lot of research on clayart and in
>all of my pottery books but it doesn't look good...
> I am using 2 types of low fire earthenware clay with silica sand and
>some grog, white and terracotta. I bisque at cone 04 for the white and
>05 for the red, oxidation in an electric kiln. I glaze at 06.
> What I have come to understand is that the primary cause of glaze
>flaking is due to too high of a clay content in the glaze and it is
>recommended that you substitute half of the kaolin for calcined kaolin,
>taking into account the loss of weight. I am certain that this is the
>main cause of my problem but none of my books specify what % of
>clay is too high. Is it 15%,20%, 30%?
> Another factor may be whether or not you have hard water. I know
>that ours is slightly hard and my terracotta pots have scumming. Does
>using distilled water make any difference concerning glaze flaking?
> I use an alkaline base glaze recipe and adding oxides from there.
>100 gr.
>Gerstley Borate- 25.8
>Ferro Frit 3269- 41.6
>Epk Kaolin - 32.6
>V gum T- 1 tsp.
>
> Surprisingly, I can still buy gerstley from Sheffield Pottery in Mass.
> After every bisque, I rince off the pots in the sink and wait for them to
>dry before glazing. This glaze needs to be dipped rather thick in order
>for it to look "right". I get these fantastic star patterns in the glaze.
>Earlier, I had problems with my glaze not drying on the pots. I would
>have to wait 24 hours for 1 coat of glaze to dry! So, I added 2% epsom
>salt solution to the glaze and that has helped with the drying. Now, I
>can dip my second coat in about 3 minutes but it still takes hours for
>the glaze to dry completely.
> I have tried applying the glaze thinner and found that it does not flake
>off of the bisque but it's too thin. I have also dampened the pots
>before dipping and it flakes. I have not rinced the bisque and it flakes.
>And I have brushed on the glaze and it still flakes. I should also
>mention that my glaze (or clay) has a lot of pinholes not just on the foot
>of the pot where I trim. My only solution now is to reglaze and refire,
>but this is becoming too time consuming and too expensive. Is there
>any hope of saving these glazes or do I have to start over with new
>batches using calcined kaolin?
> Patiently waiting for responses or a high fire kiln and stoneware.
> Trish
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Trish Messenger on thu 1 apr 04
Hello Ron,
Thanks for offering to take a look at my glaze. I'm
not sure if you recieved my last message to you...
c06 Clear Gloss Glaze 100 gr.
Gerstley Borate- 25.8
Ferro Frit 3269- 41.6
Epk Kaolin - 32.6
Add
V gum T- 1 tsp.
Any suggestions you can offer would be greatly
appreciated.
Thanks,
Trish
--- Ron Roy wrote:
> Hi Trish,
>
> For one thing - adding Epsom salts is exactly the
> wrong thing to add - it
> focculates a glaze - which means you need more water
> - which increases the
> shrinkage - which is one reason your glaze is
> cracking during drying.
>
> Send me your current recipe and I will see if I can
> make some beneficial
> changes.
>
> RR
>
>
> > I could really benefit from some suggestions on
> how to save my 30
> >gallons of glaze. I have been doing a lot of
> research on clayart and in
> >all of my pottery books but it doesn't look good...
> > I am using 2 types of low fire earthenware clay
> with silica sand and
> >some grog, white and terracotta. I bisque at cone
> 04 for the white and
> >05 for the red, oxidation in an electric kiln. I
> glaze at 06.
> > What I have come to understand is that the
> primary cause of glaze
> >flaking is due to too high of a clay content in the
> glaze and it is
> >recommended that you substitute half of the kaolin
> for calcined kaolin,
> >taking into account the loss of weight. I am
> certain that this is the
> >main cause of my problem but none of my books
> specify what % of
> >clay is too high. Is it 15%,20%, 30%?
> > Another factor may be whether or not you have
> hard water. I know
> >that ours is slightly hard and my terracotta pots
> have scumming. Does
> >using distilled water make any difference
> concerning glaze flaking?
> > I use an alkaline base glaze recipe and adding
> oxides from there.
> >100 gr.
> >Gerstley Borate- 25.8
> >Ferro Frit 3269- 41.6
> >Epk Kaolin - 32.6
> >V gum T- 1 tsp.
> >
> > Surprisingly, I can still buy gerstley from
> Sheffield Pottery in Mass.
> > After every bisque, I rince off the pots in the
> sink and wait for them to
> >dry before glazing. This glaze needs to be dipped
> rather thick in order
> >for it to look "right". I get these fantastic
> star patterns in the glaze.
> >Earlier, I had problems with my glaze not drying on
> the pots. I would
> >have to wait 24 hours for 1 coat of glaze to dry!
> So, I added 2% epsom
> >salt solution to the glaze and that has helped with
> the drying. Now, I
> >can dip my second coat in about 3 minutes but it
> still takes hours for
> >the glaze to dry completely.
> > I have tried applying the glaze thinner and found
> that it does not flake
> >off of the bisque but it's too thin. I have also
> dampened the pots
> >before dipping and it flakes. I have not rinced
> the bisque and it flakes.
> >And I have brushed on the glaze and it still
> flakes. I should also
> >mention that my glaze (or clay) has a lot of
> pinholes not just on the foot
> >of the pot where I trim. My only solution now is
> to reglaze and refire,
> >but this is becoming too time consuming and too
> expensive. Is there
> >any hope of saving these glazes or do I have to
> start over with new
> >batches using calcined kaolin?
> > Patiently waiting for responses or a high fire
> kiln and stoneware.
> > Trish
>
> 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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Ron Roy on fri 2 apr 04
Hi Trish,
I don't have a lot od experience at low fire but you are welcome to try
this revision to see if it works - you may also be able to add a little of
the glaze you have mixed to it - you will just have to experiment.
Test this first 1000 grams - to see if it works.
Gerstly Borate - 16.0
Frit 3269 - 60.0
EPK - 15.0
Calcined Kaolin - 9.0
Total 100.0
Don't use any macaloid or bentonite - or Epsom salts.
RR
>Hello Ron,
> Thanks for offering to take a look at my glaze. I'm
>not sure if you recieved my last message to you...
> c06 Clear Gloss Glaze 100 gr.
> Gerstley Borate- 25.8
> Ferro Frit 3269- 41.6
> Epk Kaolin - 32.6
> Add
> V gum T- 1 tsp.
> Any suggestions you can offer would be greatly
>appreciated.
> Thanks,
> Trish
>> >100 gr.
>> >Gerstley Borate- 25.8
>> >Ferro Frit 3269- 41.6
>> >Epk Kaolin - 32.6
>> >V gum T- 1 tsp.
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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