Josh Berkus on wed 8 oct 08
Kelley,
> So. Glazed, or unglazed? The goal is to withstand the winter weather,
> though he expects to have to replace the whole works every six months or
> so (thermocouple and all.) If these did crack, it wouldn't effect their
> utility, just the possibility of further use once disassembled.
Well, you really need an Alfred grad for this kind of question. Nearest point
of refrence I have: the ceramic pole-tops used with high-tension electric
wires are glazed.
But ... when I've seen ceramics used for high-temp/high-voltage use, it's
generally been a high-temp (cone 11-12) porcelain rather than stoneware. I
don't know specifically why, but that's what I've seen.
--
Josh "the Fuzzy" Berkus
San Francisco
Sherron & Jim Bowen on wed 8 oct 08
they glaze insulators used on power transmission equipment and they glaze
insulators used on electric fences.
JB
----- Original Message -----
From: "Kelly Savino"
To:
Sent: Wednesday, October 08, 2008 7:37 PM
Subject: clay brackets: weather/thermal shock advice needed
Kelly Savino on wed 8 oct 08
OK, with all this talk of following your inner arteest, I got all
inspired and took a new commission which is o so ethereal:
I am making ceramic clamps to hold thermocouples to auto-sparking
torches on a landfill, the kind made to burn off the methane gas emitted
by the underground decomposition.
I made a few prototypes and cut an extruder die in the shape of a cross
section of the factory produced rubber piece I was given (uh, apparently
those melt) and now that the initial R&D is out of the way, I can
produce the required hundred or so.
The first batch will be tested on site, over the coming months, and
while I am ok with my clay body (a groggy classroom stoneware that
claims to go from raku to ^10) I am debating with a friend over whether
these should be glazed or unglazed.
They should be relatively protected from thermal shock during use,
though apparently in high wind the flames can lick down toward the
bracket. They will be held in a metal clamp, and the long, thin, metal
thermocouple that passes through the channel in the center of this
two-piece ceramic doodad will be wrapped in a thin blanket of insulation
(he'd been using fiberglass with little success, so I explained what
kaowool is and where to get it.)
So. Glazed, or unglazed? The goal is to withstand the winter weather,
though he expects to have to replace the whole works every six months or
so (thermocouple and all.) If these did crack, it wouldn't effect their
utility, just the possibility of further use once disassembled.
My current plan is to give him test samples of both sorts, and see what
works best. It also occurred to me to try to fire a set below
vitrification, though I imagine on second thought that porosity could
lead to spalling.
I'm wide open to suggestions, here... including (ahem) what to charge,
for the set up, and then per item -- (on or off list works for me, since
this might not be the kind of project of interest to most.).
Now... let me adjust my beret and go commune with my muse...
Yours
Kelly in Ohio... canning plums, inventorying and defrosting freezers
this week, stocking the pantry while the radio sings the wall street
blues... trying to find inventive things to do with those remaining
venison blade roasts before November brings better cuts again...
http://www.primalpotter.com
Paulette Carr on thu 9 oct 08
Kelly,
Maybe not ethereal, but challenging: I would suggest that you use an
architectural clay body for your brackets/clamps. Many of those clay
bodies are low-fire, both red and white. I can personally vouch for
the white talc body that I use and fire to ^03, with and without
glazes. The tiles and boxes that I made up to 17 years ago, live
outside year round in one of this country's premier freeze-thaw
environments with nary a spall, or crack. Eleanora Eden mentioned to
me several times that she had observed the same thing with some her
talc-body pieces that she had left out of doors for a prolonged
periods (i.e., years). I should also mention that there is quite a
lot of grog in the body (from 10-25% depending upon the pieces), and
that should work fairly well for thermal shock and freeze-thaw
problems. The proper clay body would not require additional
insulation from the weather. One of the benefits of the talc body is
that it does not absorb water and swell the way that a terracotta
body does. If you prefer a red clay and want to work at ^6, then Val
Cushing has a recipe for an architectural clay body, p.17. I believe
some very effective ceramic brackets could be produced at lower
temperatures/heat work than you are planning - effectively reducing
your carbon footprint. My initial impulse would be to use an
unglazed bracket, unless you could make very certain that over time
and under the conditions that the brackets will be used, the glaze
fit will not produce problems.
With regard on what to charge... assume an hourly rate for product
development, and molds/dies. Since the mold and die work is already
finished, but the testing and final materials are not, I would charge
a flat fee for the product development/set up - I normally charge
$40-50/real hour. I would estimate time and materials (including
wear and tear of machinery, kiln etc.), plus a profit. Play around
with the profit until you feel comfortable with what you will be
asking/getting. If he is going to order great volumes, you could
even reduce the cost per piece with the size of the order. Remember,
this is industrial work, not art, and can be lucrative, but make
certain that you copyright or even patent the design, and all you do.
From your comment to Mel on low-fired work, I surmise that you feel
fairly negative about it (low-fired work). Just to let you know, I
make all my own glazes from what I consider non-toxic ingredients...
nepheline syenite, gillespie borate, Frit 3134, spodumene, flint,
EPK, ball clay and bentonite, with iron oxide and various mason
stains for colorants... nothing much different than you might use at
^6 or even ^10... and all specifically developed and tested to fit my
clay body. Which low-fire melters do you consider to be "bad juju"?
Please, also, let me re-assure you that I dry all excess glazes, and
dispose of them in my dry trash, trusting that they will go back to
the earth (in this case a landfill) from whence they came. I do not
pour them on my lawn or garden, only because I do not want to upset
the proper chemistry of the soils for the plants in my gardens, in
which I take such pleasure...
In any event, once you have considered that a low-fire
architectural clay body might have great function for your
application, you might develop a new respect for firing at low
temperatures, and those who chose to do it. We are not necessarily
uninformed dilettantes. If you have any questions, please feel free
to contact me.
Best of luck in your endeavors!
Paulette Carr
Paulette Carr Studio
St. Louis, MO
Member Potters Council
from "I hate to argue with Mel, but...", Kelly Savino
wrote:
In that same vein, remember that potters like you who don't buy their
glazes in little jars, and don't fire at low temps, can MAKE a glaze out
of clays and feldspars and non-toxic mined materials. Some of those
lowfire melters on the market are bad juju. One size of advice might not
fit all.
from "clay bracket: weather/thermal shock advice needed", Kelly
Savino wrote:
OK, with all this talk of following your inner arteest, I got all
inspired and took a new commission which is o so ethereal:
I am making ceramic clamps to hold thermocouples to auto-sparking
torches on a landfill, the kind made to burn off the methane gas emitted
by the underground decomposition.
I made a few prototypes and cut an extruder die in the shape of a cross
section of the factory produced rubber piece I was given (uh, apparently
those melt) and now that the initial R&D is out of the way, I can
produce the required hundred or so.
The first batch will be tested on site, over the coming months, and
while I am ok with my clay body (a groggy classroom stoneware that
claims to go from raku to ^10) I am debating with a friend over whether
these should be glazed or unglazed.
They should be relatively protected from thermal shock during use,
though apparently in high wind the flames can lick down toward the
bracket. They will be held in a metal clamp, and the long, thin, metal
thermocouple that passes through the channel in the center of this
two-piece ceramic doodad will be wrapped in a thin blanket of insulation
(he'd been using fiberglass with little success, so I explained what
kaowool is and where to get it.)
So. Glazed, or unglazed? The goal is to withstand the winter weather,
though he expects to have to replace the whole works every six months or
so (thermocouple and all.) If these did crack, it wouldn't effect their
utility, just the possibility of further use once disassembled.
My current plan is to give him test samples of both sorts, and see what
works best. It also occurred to me to try to fire a set below
vitrification, though I imagine on second thought that porosity could
lead to spalling.
I'm wide open to suggestions, here... including (ahem) what to charge,
for the set up, and then per item -- (on or off list works for me, since
this might not be the kind of project of interest to most.).
Kelly Savino on thu 9 oct 08
Paulette, thanks for the advice and information. I'm printing it for my
file, and consider it extremely helpful.
I do feel the need to rush to my own defense on the low fire issue! I am
sitting here drinking my morning coffee out of my favorite Ann Tubbs
majolica coffee mug, and much of what I "collect" is the kind of
painterly, low fired ware I don't/can't make myself. I know "cone
snobbery" is out there, but it's not one of my particular blind spots.
My understanding -- and correct me if I am wrong -- is that at a high
enough temperature, you can make glazes out of clay and stone and the
kinds of "inert", safe materials mel is talking about. At lower temps,
lead and similar materials are often required as melters.
I take issue with mel's sweeping statements about glaze being made of
just natural safe materials. He maybe forgets that many potters, whose
interests lie more with surface design than glaze formulation, are
perfectly happy to purchase their materials and don't know (or need to
know) what's in them. He maybe forgets that there are schoolteachers
using the same row of jars from the supply cabinet that have been around
since the 70s, or that some raku artist might read his post and believe
that their glaze materials, too, require no particular cautions.
Nobody said "dilettante", though I understand the tendency to be prickly
on this issue, as it has been a bone of contention in the past. I have
no conviction that every clay artist needs to be a chemist, electrician,
kiln builder and clay mixer. The kind of painterly perfection Ann Tubbs
applies to her work takes such time and attention, that how or whether
she makes her own glazes would be irrelevant, to me.
But the jars of barium, cadmium, radioactives and mystery stuff are
still out there. Boxes of it get donated to our guild, from time to
time, out of somebody's basement; I have seen it in classrooms and hobby
shops. People should NOT spray those glazes without protection, outside
or inside -- nor dump them on the roses -- nor hand them to kids like
the girl in that at with rainbow-stained hands and a paintbrush in her
mouth.
That was my only intent in addressing mel's comment. No sneer implied.
Yours
Kelly in Ohio
http://www.primalpotter.com
Paulette Carr on thu 9 oct 08
Kelly,
Perhaps I am a little prickly, but when someone mentions low-fire
work in a dismissive manner, I feel obligated to open the window of
education just a crack. Though the word "dilettante" is mine, you
did specifically say, "that potters like you [Mel] who don't buy
their glazes in little jars, and don't fire at low temps, can MAKE a
glaze out of clays and feldspars and non-toxic mined materials.". I
am not personally feeling slighted/injured or argumentative, just
opening that information window... and making an effort to correct
your impression. Like all clay work, low-fire work comes in many
flavors, not just the painterly majolica of Ann Tubbs, Linda
Arbuckle, and others... why there are even some crystalline glazes in
this temperature range in the forms of adventurines. I am in the
middle of glazing a 7' x 8' mosaic mural, built from a low-fire talc
clay body, and made with glazes developed from the materials that I
mentioned in my earlier communication - nepheline syenite, gillespie
borate, Frit 3134, flint, EPK, OM4 ball clay, bentonite, and
macaloids, Fe2O3 and mason stains... no lead, no "bad juju".
Your information regarding the making of low-fire glazes is a little
dated: To the best of my knowledge, there are very, very few
contempory potters/ceramic artists that use lead any more (and have
not for many years!). Apparently, a non-leaded glaze is not the same
as a lead glaze in terms of flow and surface, but I never used Pb -
never would, and do not know what I am missing... which in my opinion
is not much. Many potters use manganese, barium, cadmium,
radioactives (lanthanides and actinides), copper, chromium, cobalt.
They fire at many temperatures, so these potentially dangerous heavy
metals are not limited to the low-fire potters to whom you alluded.
IMO, if you undertake to use these materials, then you must be aware
of the hazards in handling, use them safely (for yourself and
others,), dispose of them properly, and finally, place them on
surfaces that are not fugitive in use. I think that if you checked
the current issue of manufactured glazes, you would find few made
with lead, and if they are, it must be on the label. As you know,
what you usually receive in the form of donated materials are
materials that have not been readily available or used for years.
Hopefully, all teachers will be required to read labels and ask
questions before allowing their students to use potentially dangerous
materials - or have the good common sense to be concerned.
One can make a perfectly safe and stable glaze that fits a given clay
body at any temperature - EVEN at low-fire temperatures. If it were
possible to check the Clayart archives, you would find many entries
for low-fire glaze recipes sans the objectionable materials. A quick
check of more recent literature will net you many "safe" glaze
recipes... and then you must make them work for your clay body at
your temperature, and the way in which you work and fire.
If you are drinking from anyone's mugs, or eating off of their
dishes, I would hope that you would be as concerned about whether and
how they make their glazes, as you are - and rightly should be! -
with their modus operandi for disposal. Enjoy your coffee in your
amazing mug! I am eager to hear of the progress on your commission.
My best,
Paulette Carr
Paulette Carr Studio
St. Louis, MO
Member Potters Council
On Oct 9, 2008, at 9:39 AM, Kelly Savino wrote:
> Paulette, thanks for the advice and information. I'm printing it
> for my file, and consider it extremely helpful.
>
> I do feel the need to rush to my own defense on the low fire issue!
> I am sitting here drinking my morning coffee out of my favorite Ann
> Tubbs majolica coffee mug, and much of what I "collect" is the kind
> of painterly, low fired ware I don't/can't make myself. I know
> "cone snobbery" is out there, but it's not one of my particular
> blind spots.
>
> My understanding -- and correct me if I am wrong -- is that at a
> high enough temperature, you can make glazes out of clay and stone
> and the kinds of "inert", safe materials mel is talking about. At
> lower temps, lead and similar materials are often required as melters.
>
> I take issue with mel's sweeping statements about glaze being made
> of just natural safe materials. He maybe forgets that many potters,
> whose interests lie more with surface design than glaze
> formulation, are perfectly happy to purchase their materials and
> don't know (or need to know) what's in them. He maybe forgets that
> there are schoolteachers using the same row of jars from the supply
> cabinet that have been around since the 70s, or that some raku
> artist might read his post and believe that their glaze materials,
> too, require no particular cautions.
>
> Nobody said "dilettante", though I understand the tendency to be
> prickly on this issue, as it has been a bone of contention in the
> past. I have no conviction that every clay artist needs to be a
> chemist, electrician, kiln builder and clay mixer. The kind of
> painterly perfection Ann Tubbs applies to her work takes such time
> and attention, that how or whether she makes her own glazes would
> be irrelevant, to me.
>
> But the jars of barium, cadmium, radioactives and mystery stuff are
> still out there. Boxes of it get donated to our guild, from time to
> time, out of somebody's basement; I have seen it in classrooms and
> hobby shops. People should NOT spray those glazes without
> protection, outside or inside -- nor dump them on the roses -- nor
> hand them to kids like the girl in that at with rainbow-stained
> hands and a paintbrush in her mouth.
>
> That was my only intent in addressing mel's comment. No sneer implied.
>
> Yours
> Kelly in Ohio
>
>
>
> http://www.primalpotter.com
Sherron & Jim Bowen on thu 9 oct 08
for Kelly's purpose I would think vitreous porcelain would be most suitable.
Look to what industry does in similar situations.
JB
----- Original Message -----
From: "Paulette Carr"
To:
Sent: Thursday, October 09, 2008 12:51 PM
Subject: Re: clay brackets: weather/thermal shock advice needed
> Kelly,
Vince Pitelka on thu 9 oct 08
Kelly Sovino wrote:
" So. Glazed, or unglazed? The goal is to withstand the winter weather,
though he expects to have to replace the whole works every six months or
so (thermocouple and all.) If these did crack, it wouldn't effect their
utility, just the possibility of further use once disassembled."
Kelly -
This is pretty straightforward. They should be unglazed. Someone else
mentioned that porcelain electrical insulators are glazed, but that is a
completely different situation with no bearing upon this one. You are
dealing with heat, and a glazed piece would be less thermal-shock-resistant.
There would be no advantage at all to glazing them. Hard freezing will have
no effect on such a small piece.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
Snail Scott on thu 9 oct 08
On Oct 8, 2008, at 8:37 PM, Kelly Savino wrote:
> ...clamps to hold thermocouples to auto-sparking
> torches on a landfill, the kind made to burn off the methane gas
> emitted
> by the underground decomposition.
> ...whether
> these should be glazed or unglazed.(?)
>
I would go with fully vitrified but unglazed.
Underfired could lead to spalling, as you say,
even though they are in close proximity to flame
(which ought to keep them dry). If they do end up a little
underfired, unglazed will survive better than glazed,
since moisture can be released and not trapped.
-Snail
Ric Swenson on fri 10 oct 08
Someone postulated that in 10=2C000 years=2C what will be left of all our o=
ld automobiles will be just the high-fired=2C glazed porcelain spark plugs.=
..all the other metal and rubber and plastic will degrade but the porcelain=
will look like new. =20
=20
=20
=20
=20
=20
I think high fired with a glaze will last a very long time. Maybe overkill=
?
=20
=20
=20
=20
Ric
=20
=20
=20
> they glaze insulators used on power transmission equipment and they glaze=
> insulators used on electric fences.> JB> > ----- Original Message -----> =
From: "Kelly Savino" > To: .ORG>> Sent: Wednesday=2C October 08=2C 2008 7:37 PM> Subject: clay bracket=
s: weather/thermal shock advice needed
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