Ron Roy on sat 29 apr 06
Hi Fred,
Probably just not fired high enough - you will find very few glazes melting
properly at cone 6 without boron or zinc. 10% Lithium carb can produce
spectacular fit problems on some clays - like crazing and shivering at the
same time.
Note the warning - this glaze is NOT recommended as a liner glaze - it will
release Barium and Lithium into food - both are toxic. If colours are used
there will be colour changes if in contact with acidic food as well.
If you really want to use this at cone 6 you would need to add either boron
or zinc.
RR
>I recently did a test firing with a good many tests. One result is
>completely baffling to me. I used the recipe for "Velvety Matte Barium
>Cone 6 to 8 Base Glaze" from Rhodes/Hopper "Clay and Glazes for the
>Potter" with colorants added. It came out looking like the front side of
>a meteorite -- hardly "velvety matte." You can see the results at
>http://www.engwrite.com/glaze test 0406/glaze test 0406_1.htm
>
>I fired to cone 6 in oxidation. If anyone has experience with this and
>can comment, I'd appreciate it.
>
>Fred Parker
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
F. Parker on sun 30 apr 06
Hi Ron:
Thanks for your reply. Somewhere (although I cannot find it now) I
thought I read that boron had a significant adverse efect on barium fluxed
glazes. Maybe it changes the frosty matte to gloss? Do you have any
knowledge of this? ALso, for either boron additions or zinc additions,
can you suggest an amount to bring the maturity to the ^6 range?
Everything I do is glazed at ^6, and I need a "frosty matte" surface, so
I'm hoping to keep it to ^6.
Re safety, nothing I will use this on is "functional" in the sense food
will be in contact. Your warning is good however, and I think it deserves
more discussion. Most of what we hear about barium relates to leaching
into the food chain. However, because of how I plan to use it (decorative
only -- no food contact) I am more concerned with the risks of having the
unaware accidentally get into a bucket of barium carbonate-containing
liquid in the studio than I am of chemical leaching. Is this a valid
concern? If so I wonder why we don't hear more discussion about it among
potters with children and pets... I'm guessing that if, instead of barium
salts the flux was strychnine, then there would be much talk about it.
I'd be interested in hearing your thoughts on this...
Regards,
Fred Parker
On Sat, 29 Apr 2006 13:12:43 -0500, Ron Roy wrote:
>Hi Fred,
>
>Probably just not fired high enough - you will find very few glazes
melting
>properly at cone 6 without boron or zinc. 10% Lithium carb can produce
>spectacular fit problems on some clays - like crazing and shivering at the
>same time.
>
>Note the warning - this glaze is NOT recommended as a liner glaze - it
will
>release Barium and Lithium into food - both are toxic. If colours are used
>there will be colour changes if in contact with acidic food as well.
>
>If you really want to use this at cone 6 you would need to add either
boron
>or zinc.
>
>
>
>RR
>
>
>>I recently did a test firing with a good many tests. One result is
>>completely baffling to me. I used the recipe for "Velvety Matte Barium
>>Cone 6 to 8 Base Glaze" from Rhodes/Hopper "Clay and Glazes for the
>>Potter" with colorants added. It came out looking like the front side of
>>a meteorite -- hardly "velvety matte." You can see the results at
>>http://www.engwrite.com/glaze test 0406/glaze test 0406_1.htm
>>
>>I fired to cone 6 in oxidation. If anyone has experience with this and
>>can comment, I'd appreciate it.
>>
>>Fred Parker
>
>Ron Roy
>RR#4
>15084 Little Lake Road
>Brighton, Ontario
>Canada
>K0K 1H0
>
>__________________________________________________________________________
____
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
Ron Roy on mon 1 may 06
Hi Fred,
I don't have direct experience to comment on how much boron it would take
to stop the matting effect of a high barium glaze. It is true that boron
never does crystallize so there is some effect.
Perhaps a combination of zinc and boron would be the answer but don't try
that in reduction.
There is a cone 6 zinc glaze in our book - 10 ZnO and 36 Neph Sy for instance.
We also have some very nice semi matte high calcium glazes that may make a
lot more sense than the barium - they do need some slow cooling.
The water in a barium glaze bucket will be a danger to pets etc. - there
was someone who wrote into ClayArt about two cats - one died and the other
was having seizures - so you are correct to be concerned - barium was the
rat poison of choice - maybe still is.
RR
>Thanks for your reply. Somewhere (although I cannot find it now) I
>thought I read that boron had a significant adverse efect on barium fluxed
>glazes. Maybe it changes the frosty matte to gloss? Do you have any
>knowledge of this? ALso, for either boron additions or zinc additions,
>can you suggest an amount to bring the maturity to the ^6 range?
>Everything I do is glazed at ^6, and I need a "frosty matte" surface, so
>I'm hoping to keep it to ^6.
>
>Re safety, nothing I will use this on is "functional" in the sense food
>will be in contact. Your warning is good however, and I think it deserves
>more discussion. Most of what we hear about barium relates to leaching
>into the food chain. However, because of how I plan to use it (decorative
>only -- no food contact) I am more concerned with the risks of having the
>unaware accidentally get into a bucket of barium carbonate-containing
>liquid in the studio than I am of chemical leaching. Is this a valid
>concern? If so I wonder why we don't hear more discussion about it among
>potters with children and pets... I'm guessing that if, instead of barium
>salts the flux was strychnine, then there would be much talk about it.
>
>I'd be interested in hearing your thoughts on this...
>
>Regards,
>
>Fred Parker
>
>On Sat, 29 Apr 2006 13:12:43 -0500, Ron Roy wrote:
>
>>Hi Fred,
>>
>>Probably just not fired high enough - you will find very few glazes
>melting
>>properly at cone 6 without boron or zinc. 10% Lithium carb can produce
>>spectacular fit problems on some clays - like crazing and shivering at the
>>same time.
>>
>>Note the warning - this glaze is NOT recommended as a liner glaze - it
>will
>>release Barium and Lithium into food - both are toxic. If colours are used
>>there will be colour changes if in contact with acidic food as well.
>>
>>If you really want to use this at cone 6 you would need to add either
>boron
>>or zinc.
>>
>>
>>
>>RR
>>
>>
>>>I recently did a test firing with a good many tests. One result is
>>>completely baffling to me. I used the recipe for "Velvety Matte Barium
>>>Cone 6 to 8 Base Glaze" from Rhodes/Hopper "Clay and Glazes for the
>>>Potter" with colorants added. It came out looking like the front side of
>>>a meteorite -- hardly "velvety matte." You can see the results at
>>>http://www.engwrite.com/glaze test 0406/glaze test 0406_1.htm
>>>
>>>I fired to cone 6 in oxidation. If anyone has experience with this and
>>>can comment, I'd appreciate it.
>>>
>>>Fred Parker
>>
>>Ron Roy
>>RR#4
>>15084 Little Lake Road
>>Brighton, Ontario
>>Canada
>>K0K 1H0
>>
>>__________________________________________________________________________
>____
>>Send postings to clayart@lsv.ceramics.org
>>
>>You may look at the archives for the list or change your subscription
>>settings from http://www.ceramics.org/clayart/
>>
>>Moderator of the list is Mel Jacobson who may be reached at
>melpots@pclink.com.
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
John Hesselberth on mon 1 may 06
On May 1, 2006, at 12:23 PM, Ron Roy wrote:
> The water in a barium glaze bucket will be a danger to pets etc. -
> there
> was someone who wrote into ClayArt about two cats - one died and
> the other
> was having seizures - so you are correct to be concerned - barium
> was the
> rat poison of choice - maybe still is.
It may be worthwhile to note that Ron is talking about the barium of
choice for potters which is barium carbonate. It is partly water
soluble and very poisonous.
Barium sulfate emulsion, that chalky, thick, yucky stuff that you may
get handed by a nurse or x-ray technician (have you noticed they
usually have an evil grin when they say 'bottoms up') when they are
about to perform one of those delightful diagnostic tests that we
(mostly older) folks get introduced to at some point in our lives is
not water soluble and passes right through the body without being
absorbed.
So please don't freak out when that friendly nurse/technician hands
you a pint or two of barium sulfate to drink. He/she is not trying to
poison you although you might find yourself wanting to run--not walk,
run--well, I did say it passes right through--to the nearest bathroom
not too long after you ingest it--don't ask me how I know this.
But do be extremely careful if you choose to handle barium carbonate
in your pottery studio. Treat it like what it is--rat poison.
Regards,
John
Paul Lewing on mon 1 may 06
on 5/1/06 11:11 AM, John Hesselberth at hesselberth@MINDSPRING.COM wrote:
> But do be extremely careful if you choose to handle barium carbonate
> in your pottery studio. Treat it like what it is--rat poison.
Another choice is a barium frit. I have no idea whether the barium in a
frit is any more or less dangerous than barium carbonate, but there are
several available. I use them mostly in glossy glazes, rather than the
standard barium mattes. Introduced in the form of a frit barium is far more
active a flux than in the carbonate form, almost as good a melter as lead.
The two I use are CC257, whose manufacturer I do not know, and Ferro 3289.
The CC257 is mostly barium and silica, and the 3289 has silica and also
barium and boron in about equal proportions. Glossy barium glazes can
produce some really bright colors. Food safety in, of course, another
issue.
Paul Lewing, Seattle
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