Cindy Strnad on tue 6 jun 00
Janet,
I think the SIO glaze would probably be okay for use on food containers,
though I haven't entered it into my insight program. I don't know if the
lithium from the Gibby's would migrate out or not, but I would think that
having the SIO on top would limit one's exposure. I'm going to be testing
with this, soon, also. It's very beautiful, isn't it? I think the only way
we're going to know for sure is to send the results off to be tested.
Cindy Strnad
earthenv@gwtc.net
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
John Hesselberth on tue 6 jun 00
BAMmusic@aol.com wrote:
>I was impressed with Stephen's Pottery page too. I'm firing my first test
>now of the Saturated Iron oxide glaze & Gibby's Khaki. After some scanning
>of the postings here, it sounds like these glazes may not be safe to use on
>mugs, pitchers, bowls, etc. I find this a bit confusing, because, on
>Stephen's page, those are precisely the types of examples he is showing. I
>would appreciate getting some info about this, because I'd love to use those
>glazes if they are safe.
>Thank You!
>Janet Bacus
>Janet@BacusAudioand Music.com
Hi Janet,
The simple fact is no one knows what is "food safe" or not. There are
only opinions. They range from "it should leach less than would be
allowed in drinking water" to "don't worry about it--there is not a
single documented case of anyone having been harmed by a lead free
glaze". The truth is probably somewhere in between, but there is NO data
except for lead and possibly cadmium.
To me it is a matter of good craftsmanship. Do you want your glazes to
be as inert as possible? Or do you not care if they leach miscellaneous
materials into your customer's food? I feel, as a matter of good
craftsmanship, we should be trying to make our glazes as stable as
possible when they may contact food surfaces and certainaly stable enough
to be durable in use. Probably only a few per cent of today's potters
feel this way (and most of them are on Clayart). In fact only a few per
cent even recognize this is something they should think about. Gibby's
Kaki is one of those inbetween glazes. It may well be stable enough to
be durable in use, but it does leach measureable amounts of lithium
(7.32mg/l) in the standard leaching test. It has a marginal level of
silica so I wouldn't expect it to be a particularly durable glaze. Note
though that it has only been tested one time that I am aware of--if you
test it, you may find it to be better or worse depending on your specific
situation. If you really like it, test it yourself and see how it
performs in your studio.
Ron Roy would not be fond of this glaze for an additional reason. Ron
just posted yesterday that he has seen too many lithium containing glazes
(this one has 10.5% lithium carbonate) craze and/or shiver and some being
so bad they actually come off a pot in small, sharp chips--that's not
exactly what your customer needs with her morning coffee. I have no idea
if Gibby's kaki shows this tendendcy or not; however I'd certainly be on
the alert for it if I decided to test or use it. It may show it on some
clays and not on others.
So you have to decide for yourself. This is a gray area and there are no
rules, laws, regulations, etc. to guide you. Only your personal
judgement. My own judgement says this is not a glaze I would put on food
surfaces knowing what I know today. 2 or 3 years ago I probably would
have. But I now know there are plenty of attractive glazes that are
significantly more stable/durable than Gibby's Kaki. Of course you can
always take the approach Ray Aldridge suggested a couple days ago of
using it on the outside and a liner glze on the inside of your pots.
Quite a number of people use that approach and are very happy with it.
Our craft is evolving and we learn more all the time. The information
exchange on this wonderful forum we call Clayart is a major factor in
that evolution.
Good luck whatever you decide.
John Hesselberth
Frog Pond Pottery
P.O. Box 88
Pocopson, PA 19366 USA
EMail: john@frogpondpottery.com web site: http://www.frogpondpottery.com
"Pots, like other forms of art, are human expressions: pleasure, pain or
indifference before them depends upon their natures, and their natures
are inevitably projections of the minds of their creators." Bernard
Leach, A Potter's Book.
BAMmusic@AOL.COM on tue 6 jun 00
I was impressed with Stephen's Pottery page too. I'm firing my first test
now of the Saturated Iron oxide glaze & Gibby's Khaki. After some scanning
of the postings here, it sounds like these glazes may not be safe to use on
mugs, pitchers, bowls, etc. I find this a bit confusing, because, on
Stephen's page, those are precisely the types of examples he is showing. I
would appreciate getting some info about this, because I'd love to use those
glazes if they are safe.
Thank You!
Janet Bacus
Janet@BacusAudioand Music.com
Stephen Pilachowski on wed 7 jun 00
I am the Stephen who posted the URL with pots using Gibby's Wild
Rose Tenmoku (I call it Khaki), Floating Blue, and Saturated Iron
Oxide (SIO), and a few others.
These are some glazes I have been recently experimenting with and I
am glad to share my results (now that I have a digital camera). That
is
what this forum is all about.
With the discussion of food safety, I need to add a few things.
1. I do not trust the Khaki to be food safe. I do not use it on
the inside of pots intended for use with either human food or
cat food (don't ask about my mother-in-law).
2. I use a top glaze (SIO) over the Khaki to get what is referred to
here as the copper penny (I call it bronze) effect. I do not
know if this does any good wrt food safety.
I have not had SIO tested at Alfred's or some sort of place. Even
though the potter who gave me the recipe described it as food
safe as far as he knew, I do not sell pots with this glaze
combo, and will not until it passes such a test.
3. Even had I tested the glaze combinations, others should not
rely solely on those results. I am very grateful for the test
results
that John HesselBerth makes available (major Thanks!). Still,
we all know that everyone mixes and applies glazes differently.
I do not sell pots with any of the glazes that are shown on
my site. (Perhaps, because I am aware to their market value....)
These are the results of my recent glaze investigations with
a bunch of glazes that mostly came from Clayart. I thought that
this might interest people, and I am just thrilled to find out I
was right. Many people have sent personal email to me with
comments, questions, and suggestions - It is greatly appreciated.
One other note - I did a small number of tests using the Ron Roy
reformated version of Khaki, but the results were not to my
liking. (I add my thanks to Ron - you're great!)
Stephen Pilachowski
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