Eric Suchman on wed 9 aug 06
shellac is just an insectan exudate ( poop from a scale insect ),
soluable in alcohol. pretty sure it can't be harmful.
Eric in Oceanside
On Aug 9, 2006, at 9:11 AM, Jacqueline Miller wrote:
> Most people who use the resist technique that I like on greenware
> use orange
> shellac which fires off in the bisque. The community center where I
> work is
> not familiar with it and are worried that it will gunk up the kiln
> or will
> produce a toxic vapour. I have been using a wax instead but the one
> that I
> use takes many hours to dry and slows the process considerably. Are
> their
> worries well founded? Thank you all. Jackie
>
> --
> Jackie Miller
> JackieAMiller@gmail.com
>
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Jacqueline Miller on wed 9 aug 06
Most people who use the resist technique that I like on greenware use orange
shellac which fires off in the bisque. The community center where I work is
not familiar with it and are worried that it will gunk up the kiln or will
produce a toxic vapour. I have been using a wax instead but the one that I
use takes many hours to dry and slows the process considerably. Are their
worries well founded? Thank you all. Jackie
--
Jackie Miller
JackieAMiller@gmail.com
Veena Raghavan on thu 10 aug 06
Hi Bill,
Would you please share some recommendations on which polyurethane you use? I
have used the shellac, but don't like to do so because of the fumes, and wax
does not work as well.
Thanks in advance.
Veena
In a message dated 8/10/2006 11:14:24 AM Pacific Daylight Time,
wschran@COX.NET writes:
>
> I have my students using a water based polyurethane that when dry works well
> for the resist. Leaves a slight ash deposit after bisque firing, but comes
> right off.
>
>
> -- William "Bill" Schran
VeenaRaghavan@cs.com
William & Susan Schran User on thu 10 aug 06
On 8/9/06 12:11 PM, "Jacqueline Miller" wrote:
> Most people who use the resist technique that I like on greenware use orange
> shellac which fires off in the bisque. The community center where I work is
> not familiar with it and are worried that it will gunk up the kiln or will
> produce a toxic vapour.
A small amount will not cause problems if the kilns are properly vented.
I think more of an issue is using a resist material that is solvent or
alcohol based in an enclosed space without proper ventilation.
I have my students using a water based polyurethane that when dry works well
for the resist. Leaves a slight ash deposit after bisque firing, but comes
right off.
-- William "Bill" Schran
Fredericksburg, Virginia
wschran@cox.net
wschran@nvcc.edu
pdp1@EARTHLINK.NET on thu 10 aug 06
Hi Snail, Veena, all...
Yes, as far as I know also, Shellac would be the
most friendly/benign fumes or burn-off...
With wax or polyurethane being quite nasty/toxic
or possibly unpleasant...
Phil
Las Vegas
----- Original Message -----
From: "Snail Scott"
> At 12:11 PM 8/9/2006 -0400, you wrote:
> >...resist technique that I like...
> >shellac which fires off in the bisque. The
community center where I work is
> >not familiar with it and are worried that it
will gunk up the kiln or will
> >produce a toxic vapour. I have been using a wax
instead...
>
>
>
> I believe there is actually less 'nasty'
> burnoff from shellac than from wax. That's
> just my own sense of it, though.
>
> -Snail
Snail Scott on thu 10 aug 06
At 12:11 PM 8/9/2006 -0400, you wrote:
>...resist technique that I like...
>shellac which fires off in the bisque. The community center where I work is
>not familiar with it and are worried that it will gunk up the kiln or will
>produce a toxic vapour. I have been using a wax instead...
I believe there is actually less 'nasty'
burnoff from shellac than from wax. That's
just my own sense of it, though.
-Snail
William & Susan Schran User on fri 11 aug 06
On 8/10/06 5:55 PM, "Veena Raghavan" wrote:
> Would you please share some recommendations on which polyurethane you use=
? I
> have used the shellac, but don't like to do so because of the fumes, and =
wax
> does not work as well.
We have used Minwax=AE Polycrylic=AE and Olympic=AE water based polyurethane, but
I would imagine any water based polyurethane would work. Just have to be
sure to let it dry before you begin to scrub with water.
-- William "Bill" Schran
Fredericksburg, Virginia
wschran@cox.net
wschran@nvcc.edu
=20
Veena Raghavan on fri 11 aug 06
Thanks for the input.
Veena
n a message dated 8/10/2006 10:05:29 PM Pacific Daylight Time,
pdp1@EARTHLINK.NET writes:
>
>
> Yes, as far as I know also, Shellac would be the
> most friendly/benign fumes or burn-off...
>
> With wax or polyurethane being quite nasty/toxic
> or possibly unpleasant...
>
>
VeenaRaghavan@cs.com
Stephani Stephenson on sat 12 aug 06
I always thought shellac was derived from beetle shells, but turns out
it isn't the shell, it is the excretion....
hmmm. don;t know what the chemical composition is....vs some of the
synthetic compounds...
Following are excerpts from wikipedia entry for shellac , complete
entry at http://en.wikipedia.org/wiki/Shellac
Shellac is a brittle or flaky secretion of the lac insect Coccus lacca,
found in the forests of Assam and Thailand. Freed from wood it is
called "seedlac." Once it was commonly believed that shellac was a
resin obtained from the wings of a bug (order Hemiptera) found in
India. In actuality, shellac was obtained from an excretion of the
female bug, harvested from the bark of the trees where she deposits it
to provide a sticky hold on the trunk. There is a risk that the
harvesting process can scoop the bug up along with the secretion,
leading to its death. The natural coloration of lac residue is greatly
influenced by the sap consumed by the lac insect and the season of the
harvest. Generally in the trade of seedlac there are two distinct
colors; the orange Bysacki and the blonde Kushmi.
When purified, the chemical takes the form of yellow/ brown pellets,
this possibly providing the basis for the "Wing Source Story." Shellac
is a natural polymer and is chemically similar to synthetic polymers,
thus it is considered a natural plastic. It can be molded by heat and
pressure methods, so it is classified as thermoplastic.
It is soluble in alkaline solutions such as ammonia, sodium borate,
sodium carbonate, and sodium hydroxide, and also in various organic
solvents. When dissolved in alcohol, typically blends containing
ethanol and methanol, shellac yields a coating of superior durability
and hardness and is available in numerous grades.
Orange shellac is bleached with sodium hypochlorite solution to form
white shellac and also is produced in wax-containing and wax-free form.
Shellac is edible, and it was used as a glazing agent on pills and
candies. When used for this purpose, it has the food additive E number
E904. There were concerns that this coating is not vegetarian as it may
contain crushed bugs. In the tablet manufacture trade, it is sometimes
referred to as "beetlejuice" for this reason. Shellac is known to cause
allergies on contact, resulting in skin irritations
Shellac is now considered obsolete as a moulding compound, but its use
in industries continues as there are no synthetic or natural
substitutes in a number of processes. For examples, it is used as an
outer fruit coating to prevent post-harvest decay (e.g. apples); in
dental technology it is used in the production of custom impression
trays; it is used in the optical trade; and it was used in the
production of gramophone (phonograph) records until about 1950 (see
gramophone record for details).
For some applications a corn protein called zein is a competitive
substitute.
Stephani Stephenson
steph@revivaltileworks.com
http://www.revivaltileworks.com
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