Jim Blake on tue 13 mar 07
I got my first fish platter idea from Clayart 10 years ago and have
been happily producing great-selling fish plates ever since. Thank
you, Clayart! I'm back now with a glaze challenge. I have a
wonderful blue matt glaze that contains some barium. It's fired at
cone 7, 8, or 9. Tests done some years ago showed that while
substances such as lemon juice could cause a small amount of
leaching, it was generally safe enough for food. However some
customers are worried about it. I think the main problem is that
it's a matt version of the glaze. Does anyone have a recipe fr a
clear matt glaze that I could put over the blue to eliminate worries
about the food-safeness of the blue glaze?
Jim Blake on fri 16 mar 07
I got my first fish platter idea from Clayart 10 years ago and have
been happily producing great-selling fish plates ever since. Thank
you, Clayart! I'm back now with a glaze challenge. I have a
wonderful blue matt glaze that contains some barium. It's fired at
cone 7, 8, or 9. Tests done some years ago showed that while
substances such as lemon juice could cause a small amount of
leaching, it was generally safe enough for food. However some
customers are worried about it. I think the main problem is that
it's a matt version of the glaze. Does anyone have a recipe for a
clear matt glaze that I could put over the blue to eliminate worries
about the food-safeness of the blue glaze?
Lisa
Timothy Joko-Veltman on sat 17 mar 07
Lisa,
3 things. 1: Matte-ness tends to make a glaze opaque, and 2: while it
might be somewhat translucent, putting any glaze w/ no colourants over
another glaze is likely just to give you a new glaze, and finally, 3:
applying one glaze over the other is not a guaranteed way to make a
stable and durable glaze.
I don't want to be reactionary and say, "Don't use barium, you're
killing your customers!!!", but for whatever reason, barium and copper
(I'm assuming your barium blue is a copper blue) leach quite easily
from a glaze, especially from matte glazes. On a slightly different
tack, matte glazes also tend to mark easily with cutlery (you can test
by taking an old knife or spoon and scratch the surface of a test
piece).
Anyway, I would recommend trying to find a different solution, perhaps
find a strontium base (no, strontium is not the same as barium, but
it's closer than a lot of other fluxes, and considerably safer), or
maybe find a similarly coloured glossy glaze (the same recipe with a
lot more silica in it may be ), or maybe find a non-barium base, and
use a combination of colourants (or a stain) to achieve the colour you
are looking for.
My 2cents.
Best regards,
Tim
June Perry on sat 17 mar 07
Check Ian Currie's book. There's a beautiful matt blue that looks like a
typical, beautiful, barium blue, except it has no barium in it. He uses
strontium carb instead.
If you want you can peruse my web site. With his permission, ,I have a
picture and recipe on one of the cone 6 glaze test pages; but if you're into
making your own glazes I would very highly recommend Ian's books. They are a
wealth of information about grid testing with some lovely glaze photos and recipes
as well.
Regards,
June
http://shambhalapottery.blogspot.com/
http://www.angelfire.com/art2/shambhalapottery
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Heidy Freyre on mon 19 mar 07
On Sat, 17 Mar 2007 07:52:05 EDT, June Perry
wrote:
>Check Ian Currie's book. There's a beautiful matt blue that looks like a
>typical, beautiful, barium blue, except it has no barium in it. He uses
>strontium carb instead.
______________________________________
What are the opinions about barium frits? I wonder why they are never
mentionned on Clayart. (I am quite new at mixing my own glazes).
-BaO:1.0 Al2O3:0.51 SiO2:2.01
molecular weight: 326
firing from 855 C
classified toxic class 3, same as strontium carb
and the following one is even classified as toxic class free:
BaO 47 %, Al2O3 17 %, SiO2 36 %
formula Seger: BaO1, Al2O3 0.543, SiO2 1.953
molecular weight 326
firing 1180 - 1280 C
bariumsilicate
BTW I appreciate your website very much. All of your ^6 glazes I have
tested up to now have come out great without having had to alter anything
because of the different materials.
best regards,
heidy
John Hesselberth on mon 19 mar 07
On Mar 19, 2007, at 11:13 AM, Heidy Freyre wrote:
> What are the opinions about barium frits? I wonder why they are never
> mentionned on Clayart. (I am quite new at mixing my own glazes).
Hi Heidy,
Whether you put a material into a glaze in fritted form or as a pure
chemical compound has little or no effect on whether the glaze will
be stable or not. What matters is the composition of the glaze.
Barium frits are probably safer for the potter to handle than is
barium carbonate, but once the glaze has been melted and cooled there
would be no discernible difference in glaze stability.
Regards,
John -- who is still recovering from the trip home from NCECA. I am
sure I am luckier than some who were traveling east; however arriving
home at 3 a.m. on Sunday morning after spending all day Saturday in
airports was not a whole lot of fun. But NCECA was!! It was great to
renew acquaintances and get the creative juices stimulated. I second
those who have already said that the Clayarters' presentations were
outstanding additions to the program.
Eric Hansen on tue 20 mar 07
Iron Blue. First saw this in Iron In the Fire form the
Ashmolean - I think Nigel Wood was involved in this.
See ClayArt archives for Craig Martell's Blue Celadon
post. Korean celadon is robins-egg blue also. So use
an appropriate opacifier (no titanium?)
Boron produces a floating blue sometimes in a green
iron glaze. I think I tested nickel for a dull blue
once. Does this make sence?
H A M B O N E (E R I C H A N S E N)
--- John Hesselberth
wrote:
> On Mar 19, 2007, at 11:13 AM, Heidy Freyre wrote:
>
> > What are the opinions about barium frits? I wonder
> why they are never
> > mentionned on Clayart. (I am quite new at mixing
> my own glazes).
>
> Hi Heidy,
>
> Whether you put a material into a glaze in fritted
> form or as a pure
> chemical compound has little or no effect on whether
> the glaze will
____________________________________________________________________________________
Don't pick lemons.
See all the new 2007 cars at Yahoo! Autos.
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