Autumn Downey on fri 14 apr 00
I have made up a yellow glaze and we are testing out a bucket of it. It
work fine, except that it is VERY slow drying. According to what I've read,
this calls for a little Epsom's salts.
What confuses me is that this glaze is staying in suspension quite well -
typically the glazes needing Epsoms salts are ones that have turned to
cement at the bottom of the bucket. And in some ways when stirred, this one
seems quite thick, but gives about an average dry coating on the pot.
(Which suggests that it might in fact need Darvan or equiv.)
Opposing evidence is that I made up a batch of this glaze in Saskatchewan
where the water has much Ca & Mg and it behaves well. (Which suggests that
this glaze with our VERY soft water up here, needs Epsom's salts).
(I'm confused and as you can see, I don't want to utter the F and de-F words
- it's the way to mental breakdown). But I would appreciate it if someone
can suggest which scenario is probably the correct one. There are some
changes I would make in the next version of this glaze (reduce zn, eliminate
GB), but in the meantime would like to have this batch a little more user
friendly.
I have a couple of other observations/questions re glaze consistency as well:
1. The Ron Roy Black #3 is also a little slower in drying than other
glazes. A local water-based phenomenon?
2. For the most part, we have got along quite well with GB up here in
Yellowknife and that's probably because of our water. It might actually
help some of our glazes.
3. Are there occasions when a person might use part EPK and part ball clay
for the clay content in order to add more particle sizes? I realize
bentonite is the most common clay type suspender, but I wondered if ball
clay was an inbetween size and might have some benefits.
Thanks. I know this topic gets covered quite often, but it still has me
confused - with all the variables.
-- Autumn Downey, Yellowknife, NWT
The glaze in question:
Yellow
======
CUSTER FELDSPAR..... 32.00 29.09%
WHITING............. 12.00 10.91%
SILICA.............. 24.00 21.82%
ZINC OXIDE.......... 6.50 5.91%
EPK KAOLIN.......... 17.00 15.45%
FRIT 3134........... 6.00 5.45%
GERSTLEY BORAT...... 2.50 2.27%
TIN OXIDE........... 2.00 1.82%
titanium dioxide.... 4.00 3.64%
RUTILE.............. 4.00 3.64%
========
110.00
SnO2 0.04 1.97%
CaO 0.51* 8.41%
MgO 0.01* 0.12%
K2O 0.12* 3.33%
Na2O 0.09* 1.64%
ZnO 0.27* 6.40%
TiO2 0.34 7.88%
ZrO2 0.00 0.04%
Al2O3 0.40 11.83%
B2O3 0.10 2.05%
P2O5 0.00 0.04%
SiO2 3.18 56.11%
Fe2O3 0.00 0.18%
Cost/kg 3.24
Si:Al 8.05
SiB:Al 8.30
Expan 7.65
Notes:
makes a medium yellow gloss -
passed vinegar test
Ron Roy on mon 24 apr 00
Hi Autumn,
I don't know if this has been answered - I'm a week and a half behind - but -
First of all here is your glaze without the GB - same glaze but it won't
flock the way it did with the GB.
Custer - 29.5
whiting - 11.5
Silica - 24.0
ZnO - 6.5
EPK - 18.5
Frit 3134 - 9.5
Talc - 0.5
Tin - 2.0
TiO2 - 4.0
Rutile - 4.0
Ratio and expansion are very close to the original - I'll bet you can't
tell the difference.
The reason a glaze takes a long time to dry on a pot is because it's
flocculated - more water than it really needs for proper application.
Adding Epson salts would make that worse.
If it was the opposite problem - glaze settles out in the bucket - you
might want to add epson to help keep it suspended. I only recommend Epson
salts as a last resort - who needs solubles in the bucket unless you
absolutley need them?
The GB in this glaze - although a small amount - was probably the
flocculator. If you still find this glaze not drying fast enough - a
reformulation with a frit which contains some alumina would be one of the
answers - 3134 has no alumina for instance but 3195 would have the right
stuff.
Adding ball clay would make the problem worse if your glaze is flocculated
but a good plan if it's settling out - the next step - if settling - after
ball clay - is bentonite.
The RR black has bentonite in it - like 2% - leave it out next time. You
have some acidity in your water so your glazes are going to want to flock -
leave out the heavy duty suspenders in your recipies. If your water was
alkaline you would have to opposite problem.
RR
>----------------------------Original message----------------------------
>I have made up a yellow glaze and we are testing out a bucket of it. It
>work fine, except that it is VERY slow drying. According to what I've read,
>this calls for a little Epsom's salts.
>
>What confuses me is that this glaze is staying in suspension quite well -
>typically the glazes needing Epsoms salts are ones that have turned to
>cement at the bottom of the bucket. And in some ways when stirred, this one
>seems quite thick, but gives about an average dry coating on the pot.
>(Which suggests that it might in fact need Darvan or equiv.)
>
>Opposing evidence is that I made up a batch of this glaze in Saskatchewan
>where the water has much Ca & Mg and it behaves well. (Which suggests that
>this glaze with our VERY soft water up here, needs Epsom's salts).
>
>(I'm confused and as you can see, I don't want to utter the F and de-F words
>- it's the way to mental breakdown). But I would appreciate it if someone
>can suggest which scenario is probably the correct one. There are some
>changes I would make in the next version of this glaze (reduce zn, eliminate
>GB), but in the meantime would like to have this batch a little more user
>friendly.
>
>I have a couple of other observations/questions re glaze consistency as well:
>
>1. The Ron Roy Black #3 is also a little slower in drying than other
>glazes. A local water-based phenomenon?
>
>2. For the most part, we have got along quite well with GB up here in
>Yellowknife and that's probably because of our water. It might actually
>help some of our glazes.
>
>3. Are there occasions when a person might use part EPK and part ball clay
>for the clay content in order to add more particle sizes? I realize
>bentonite is the most common clay type suspender, but I wondered if ball
>clay was an inbetween size and might have some benefits.
>
>Thanks. I know this topic gets covered quite often, but it still has me
>confused - with all the variables.
> -- Autumn Downey, Yellowknife, NWT
>
>The glaze in question:
> Yellow
> ======
> CUSTER FELDSPAR..... 32.00 29.09%
> WHITING............. 12.00 10.91%
> SILICA.............. 24.00 21.82%
> ZINC OXIDE.......... 6.50 5.91%
> EPK KAOLIN.......... 17.00 15.45%
> FRIT 3134........... 6.00 5.45%
> GERSTLEY BORAT...... 2.50 2.27%
> TIN OXIDE........... 2.00 1.82%
> titanium dioxide.... 4.00 3.64%
> RUTILE.............. 4.00 3.64%
> ========
> 110.00
>
> SnO2 0.04 1.97%
> CaO 0.51* 8.41%
> MgO 0.01* 0.12%
> K2O 0.12* 3.33%
> Na2O 0.09* 1.64%
> ZnO 0.27* 6.40%
> TiO2 0.34 7.88%
> ZrO2 0.00 0.04%
> Al2O3 0.40 11.83%
> B2O3 0.10 2.05%
> P2O5 0.00 0.04%
> SiO2 3.18 56.11%
> Fe2O3 0.00 0.18%
>
> Cost/kg 3.24
> Si:Al 8.05
> SiB:Al 8.30
> Expan 7.65
>
> Notes:
> makes a medium yellow gloss -
> passed vinegar test
Ron Roy
93 Pegasus Trail
Scarborough
Ontario, Canada
M1G 3N8
Evenings 416-439-2621
Fax 416-438-7849
Autumn Downey on tue 25 apr 00
Hello Ron,
Thank you for your reply - and next batch of glaze I will mix the
reformulation you have done. Appreciate your time and effort for this. I
expect it will tip the balance in the right direction!
However, the glaze on hand is defying the concensus of opinion that it is
flocculated.
I tried removing a little water and adding a few drops of Darvan - but the
drying was slow and the dried glaze layer seemed fairly thick. (So I added
the water back). Next night, I wound up adding about 2 1/2 tbsp Epsom's
salt solution to what must be around 3000 g dry of this glaze - and this
improved the drying. It's not quite as good as other glazes, but it's lots
better than it was. (It was well suspended before - the addition of Epsom's
didn't make any noticeable further thickening)
Anyway, am beginning to think that although the glaze constituents (clay
and GB) suggested that the glaze was flocculated, it really wasn't (yet)
without the addition of an electrolyte. (Boy, am I getting brave, tossing
these terms around!! Never mind, Hamer is open, so I can double check.)
He says that if the clay content of a glaze is flocculated, the clay
particles take on the card house structure which allows water to pass
through it and out. I think that must have been the case with this
particular glaze. Am I wrong in thinking that slightly acidic (mineral
free) water is fairly uncommon? (Which is why I seem to be in a different
boat (here) from most other people??)
I'd also add that we tend to be quite big users of Epsom's salts - esp in
our throwing water when we use Plainsman M370 - and in a few glazes. The
cement thing happens here fairly often. My feeling was that alkaline water
was more inclined to flocculate a glaze. Or does it depend more on the
actual content of the salts than the pH?
Thanks for suggestions!
Autumn Downey
At 01:19 PM 2000-04-24 EDT, you wrote:
>----------------------------Original message----------------------------
>Hi Autumn,
>
>I don't know if this has been answered - I'm a week and a half behind - but -
>
>First of all here is your glaze without the GB - same glaze but it won't
>flock the way it did with the GB.
>
>Custer - 29.5
>whiting - 11.5
>Silica - 24.0
>ZnO - 6.5
>EPK - 18.5
>Frit 3134 - 9.5
>Talc - 0.5
>Tin - 2.0
>TiO2 - 4.0
>Rutile - 4.0
>Ratio and expansion are very close to the original - I'll bet you can't
>tell the difference.
>
>The reason a glaze takes a long time to dry on a pot is because it's
>flocculated - more water than it really needs for proper application.
>Adding Epson salts would make that worse.
>
>If it was the opposite problem - glaze settles out in the bucket - you
>might want to add epson to help keep it suspended. I only recommend Epson
>salts as a last resort - who needs solubles in the bucket unless you
>absolutley need them?
>
>The GB in this glaze - although a small amount - was probably the
>flocculator. If you still find this glaze not drying fast enough - a
>reformulation with a frit which contains some alumina would be one of the
>answers - 3134 has no alumina for instance but 3195 would have the right
>stuff.
>
>Adding ball clay would make the problem worse if your glaze is flocculated
>but a good plan if it's settling out - the next step - if settling - after
>ball clay - is bentonite.
>
>The RR black has bentonite in it - like 2% - leave it out next time. You
>have some acidity in your water so your glazes are going to want to flock -
>leave out the heavy duty suspenders in your recipies. If your water was
>alkaline you would have to opposite problem.
>
>RR
>
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