will edwards on tue 23 jan 01
Hello,
Ron is correct to alert those of the dangers of some materials where it i=
s
easily over-looked. I hope these add to his findings. Fear is not what th=
is is
about, it is a tool to educate on safety issues. I don't want to scare yo=
u! It
can be safe for everyone and as fun as it ever was once you understand th=
e
basics better.
1. If you mix glaze wear a mask and latex gloves regardless. SiO2 (Silica=
)
which is ground very fine stays in the lungs and can cause silicosis. Don=
't
fan it around. =
2. Many glazes such as manganese is far more worse by breathing fumes fro=
m it.
While it does not appear to be easily absorbed through the skin fumes are=
a
different matter. Know that you have levels of manganese (Mn) already in =
your
body and it as well as many of the earth elements are essential to good
health. Too much of it can also lead to bad health. Copper is another one=
like
that. I really like enviroventing all our kilns to the outside. We also h=
ave
full room ventilation for over-kill. Lol! I love c=
opper
as well if I can keep it in the glaze. (Lab Test)
3. The Glaze user - Once we make a glaze and it is wet does the problem s=
top
here? No, with glaze drips and spills and that sanding/scratching around =
the
bottoms getting excess glazes help create air born particles as well. If =
its
not manganese (Mn), any other toxin could be one more easily taken in by =
the
skin or in another way. Its not practical to wear a filter or dust mask a=
round
so mopping with water and a small amount of bleach should be maintained a=
nd a
good dusting of shelves every so often. Don't mix bleach with acids. Thos=
e two
combine are very dangerous! I have seen this recommended to kill bacteria=
in a
glaze bucket. If you do this carry it outside and leave it for several ho=
urs
because normal respirators will not always filter fumes like that. =
4. Airbrushing glazes - Now this one is a big time worry for me. Make ver=
y
sure you are willing to wear every possible device when using this.
Airbrushing throws micro-particles into the air that is much more prone t=
o
floating around than most dry dusts. Always use good ventilation or do it=
outside. Then use a filtration system if possible to direct it away from =
you,
your hair and your clothes.
5. The finished and fired glaze - The piece is ready to sell, is it safe?=
Lab
tests are the only accurate method for determining this. Limit formulaes =
give
you a range to start with but is not clear enough to determine the final
safety of the glaze. Cadmium (Cd), Lead (Pb), beryllium (Be), lithium (Li=
) and
barium (Ba) are the first I would look at. Copper (Cu), Cobalt (Co), Mang=
anese
(Mn), Vanadium (V) and boron (B) are others. Also we can see how many of =
these
hold up by mixing them with TiO2 and iron (Fe) or magnesium (Mg) among ot=
hers.
Each time we alter a glaze with another oxide it shifts somewhere else. I=
t may
be stronger or weaker based on the agreement of the two or three oxides a=
long
with the base.
FDA had 20 contaminates listed up to around '87 I think it was (?), now i=
t is
closer to 70+ contaminates and Sodium (Na)is included in it. Why that? So=
dium
(Na)is dangerous to some people that are on HBP medications. How much wou=
ld a
person be exposed to? Again that is determined in a lab where the scope o=
f
equipment is carefully calibrated and the technician fully trained to do =
these
tests. Yet they still have it listed they are no limits set that I can fi=
nd.
The more exposure we have to something the less our systems can tolerate =
it in
many cases. Its like developing an allergy so to speak that can make you =
very
sick or cause disease.
(Reminds me of my neighbors mother who called my Algae eater an allergy e=
ater)
Hey she don't know fish. How can we expect everyone to know all this?
Ron Roy and others who talk about the use of Vinegar 4-5% acidic solution=
are
making you aware of one of the only known home tests that is a worthy fir=
st
attempt to see if your glaze is a good one or not. Lemon slices and orang=
e
slices and other acidics over a period of time can mute or pull color fro=
m a
bad glaze. I let my glazes stay 3 days at room temperature in vinegar to =
see
if I even want to go further. If I see any change at all, I move along be=
cause
they are too many methods of making a glaze durable other-wise. I still c=
an
generally get the same effect or color I want by making those changes in
chemistry and ingredients.
Assume that Matte glazes are decorative glazes for the most part. (Not th=
at
they are always a toxic issue, but because they lack a smooth finish that=
is
needed to close pores off and some are easy to scratch. Glossy ones with =
great
shine seem to be more agreeable towards holding their color but that is n=
ot
fool-proof. Mattes are my favorite and I use them sparingly on outside pi=
eces
of food bearing dishes where 1/3 or more of the outter lip is not in cont=
act
with food and all the inside is covered with lab approved glossy glazes. =
This
way I can achieve some really neat color variations. But the other factor=
here
is, not all glazes we see people discussing are used for food bearing
purposes. Many people are after effect and they use all the safty gear fo=
r
their own use. Maybe the future will allow us to make better use of
terminology for our glazes by understanding them a little more.
Please bring any mis-directed mentions or mistakes to my attention and I =
will
fix them.
William Edwards
Alchemy 101
____________________________________________________________________
Get free email and a permanent address at http://www.netaddress.com/?N=3D=
1
Craig Martell on wed 24 jan 01
William Edwards commented:
>1. If you mix glaze wear a mask and latex gloves regardless. SiO2 (Silica)
>which is ground very fine stays in the lungs and can cause silicosis. Don't
>fan it around.
Also, if you dry mix the glaze before hydrating, do it in a covered
container that will not allow dust to escape. Dry mixing can be avoided
altogether and the dry ingredients can be added to water and allowed to
hrydrate before you start mixing. No dust! A general rule for the correct
amount of water is: 1 mililitre of water per 1 gram of dry material.
>3. The Glaze user - Once we make a glaze and it is wet does the problem stop
>here? No, with glaze drips and spills and that sanding/scratching around the
>bottoms getting excess glazes help create air born particles as well.
Most potters eliminate the bottom cleaning problem by using wax
resist. This isn't a new or revolutionary idea by any means. The excess
wet glaze falls back into the bucket and the drips are sponged off. No big
deal! If you don't want to wax you can use a wet Scotchbrite pad to scrub
off excess glaze and this won't cause an airborne dust hazard. These
practices have been in use for a long time.
>5. The finished and fired glaze - The piece is ready to sell, is it safe? Lab
>tests are the only accurate method for determining this. Limit formulaes give
>you a range to start with but is not clear enough to determine the final
>safety of the glaze.
Sorry, have to disagree a bit. Lab tests are the ONLY way to tell if a
glaze is safe IF you are using any hazardous materials. I use a feldspar,
limestone celedon that I've never had tested because there's nothing in it
that's toxic. It also has enough silica and alumina to be durable and it's
a bright, highly fused glaze at cone 10. It's my feeling that in most
cases limits based on durable models will give glazes that are fine for
domestic pots. But the ceramist has to make educated use of selected
materials to ensure this. I think that most of us have the potential to
make these choices once we do our homework. If we are uncertain about a
glaze, the lab is the next step.
>Cadmium (Cd), Lead (Pb), beryllium (Be), lithium (Li) and
>barium (Ba) are the first I would look at. Copper (Cu), Cobalt (Co), Manganese
>(Mn), Vanadium (V) and boron (B) are others.
Don't forget Chromium Oxide. It's another material that should be used
with great care.
> Also we can see how many of these hold up by mixing them with TiO2 and
> iron (Fe) or magnesium (Mg) among others.
How does mixing potentially toxic minerals with titanium, iron, or magnesia
yield any insight into their behavior in a fired glaze?
>Each time we alter a glaze with another oxide it shifts somewhere else. It may
>be stronger or weaker based on the agreement of the two or three oxides along
>with the base.
It depends too on the amount of any additonal oxide. This is usually
looked at on the molecular level against the silica and alumina. Higher
concentrations of materials that don't contain silica and or alumina will
lower the proportion of silica and alumina on the molecular level and
increase the chances that the added oxide and others cannot be bound and
held by the lesser amounts of silica. Your above statement is a bit too
hypothetical and I think you need to state specific cases to make sense of
it. Such as: what oxides you are talking about, how much you are adding,
potential problems related to specific materials and levels at which these
problems might arise.
>FDA had 20 contaminates listed up to around '87 I think it was (?), now it is
>closer to 70+ contaminates and Sodium (Na)is included in it. Why that? Sodium
>(Na)is dangerous to some people that are on HBP medications.
If you are talking about table salt raising a person's blood pressure I
would agree. If you are talking about sodium as a glaze ingredient raising
blood pressures by leaching into food, I would have to think that is a very
long shot.
>Assume that Matte glazes are decorative glazes for the most part. (Not that
>they are always a toxic issue, but because they lack a smooth finish that is
>needed to close pores off and some are easy to scratch. Glossy ones with great
>shine seem to be more agreeable towards holding their color but that is not
>fool-proof.
The use of Matt and Bright glazes with regard to their suitability as
functional glazes has been discussed at length on Clayart. With matts, it
depends on the total composition of the glaze and the degree of
mattness. With bright clear glazes, it depends too on the total
composition of the glaze and the source of glass. We can have very shiny
fused glazes that won't hold anything due to a shortage of silica. Boron
glazes are a good example of this IF the boron is high enough that it is
the major source of glass former and not silica. So you are correct in
saying that it's not "fool-prof".
One thing that hasn't been mentioned with regard to glazes not suitable for
domestic ware is,not giving them to anyone. I would assume that if I had a
glaze that wasn't suitable for domestic pots and I published it or gave it
to someone sooner or later it would end up on Aunt Becky's favorite cereal
bowl. If I didn't relinquish the formula or recipe, that would never
happen. I'm not saying that we should not give these glazes to
anyone. I'm saying that it MIGHT be prudent to withold them.
regards, Craig Martell in Oregon
Wade Blocker on thu 25 jan 01
Jennifer,
I wonder if you are confusing porosity in a glaze with staining. I have
a Corning ware- pyroceram, coffee pot that becomes stained from coffee.
Ordinary hand washing does not remove the stain, but the dishwasher will.
For those not using that appliance , chlorox solution bleaches the
discoloration. I am sure that has nothing to do with poor glaze
application. This also applies to my teapot, the tannin will discolor the
inside temporarily. Mia in ABQ
Jennifer F Boyer on thu 25 jan 01
This is interesting. Most of the mugs(cone 10) I own of other
potters are glossy. A few are matt and most of those are crazed
and get grimy. But when I bought the glossy ones, I assumed they
would be durable and resistant to residue. The thing is that
some of them still get grimy from tea residue. This washes off
with scrubbing. But my own mugs(cone 10) never develop any
residue. So this shows me that glossy glazes are not all created
equal. This residue build up has to be sticking to some sort of
texture or openness, porousity in the glossy glaze. My pea brain
has always told me that a gloss surface can't be
porous.....guess I'm wrong.
Jennifer
> The use of Matt and Bright glazes with regard to their suitability as
> functional glazes has been discussed at length on Clayart. With matts, it
> depends on the total composition of the glaze and the degree of
> mattness. With bright clear glazes, it depends too on the total
> composition of the glaze and the source of glass. We can have very shiny
> fused glazes that won't hold anything due to a shortage of silica. Boron
> glazes are a good example of this IF the boron is high enough that it is
> the major source of glass former and not silica. So you are correct in
> saying that it's not "fool-prof".
>
--
~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
Jennifer Boyer mailto:jboyer@adelphia.net
Thistle Hill Pottery
95 Powder Horn Glen Rd
Montpelier, VT 05602 USA
802-223-8926
http://www.thistlehillpottery.com/
Never pass on an email warning without checking out this site
for web hoaxes and junk:
http://urbanlegends.about.com/science/urbanlegends/cs/nethoaxes/index.htm
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John Hesselberth on thu 25 jan 01
Jennifer F Boyer wrote:
>This is interesting. Most of the mugs(cone 10) I own of other
>potters are glossy. A few are matt and most of those are crazed
>and get grimy. But when I bought the glossy ones, I assumed they
>would be durable and resistant to residue. The thing is that
>some of them still get grimy from tea residue. This washes off
>with scrubbing. But my own mugs(cone 10) never develop any
>residue. So this shows me that glossy glazes are not all created
>equal. This residue build up has to be sticking to some sort of
>texture or openness, porousity in the glossy glaze. My pea brain
>has always told me that a gloss surface can't be
>porous.....guess I'm wrong.
Hi Jennifer,
You are correct that bad glazes can be either glossy or matte. I will
try to lay this out as clearly as I know how at my NCECA presentation in
Charlotte. If you will be at NCECA please try to attend; if not I will
make the charts I use available after the conference. I have what I
believe is some very interesting data to actually demonstrate how to make
good and bad glazes.
Regards, John
"The life so short, the craft so long to learn." Hippocrates, 5th cent.
B.C.
Jennifer F Boyer on fri 26 jan 01
Hi Mia,
My question is why? What makes some glazes prone to staining and
others not? Tannin doesn't stain my own liner glaze..
Jennifer
Wade Blocker wrote:
>
> Jennifer,
> I wonder if you are confusing porosity in a glaze with staining. I have
> a Corning ware- pyroceram, coffee pot that becomes stained from coffee.
> Ordinary hand washing does not remove the stain, but the dishwasher will.
> For those not using that appliance , chlorox solution bleaches the
> discoloration. I am sure that has nothing to do with poor glaze
> application. This also applies to my teapot, the tannin will discolor the
> inside temporarily. Mia in ABQ
>
> ______________________________________________________________________________
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>
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>
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--
~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
Jennifer Boyer mailto:jboyer@adelphia.net
Thistle Hill Pottery
95 Powder Horn Glen Rd
Montpelier, VT 05602 USA
802-223-8926
http://www.thistlehillpottery.com/
Never pass on an email warning without checking out this site
for web hoaxes and junk:
http://urbanlegends.about.com/science/urbanlegends/cs/nethoaxes/index.htm
~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
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