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fecl3 and terra sig

updated thu 1 feb 07

 

Taylor Hendrix on tue 23 jan 07


Howdy everybodies,

Okay I'm just spitballing here so be kind.

I have not really been able to use my FeCl3 solution on my saggar pots
because I apply my sig to the bisqued pots, saggar, and then fire. I
have brushed FeCl3 onto bisqued ware alone but my tests last night
with raw sig and the ferric chloride were iffy. I could bring up a
shine with the terra sig but as soon as I brushed on the ferric
chloride I could not regain the shine. Oddly enough raw sig over FeCl3
would not bring up much of a shine either. Any thoughts? My next
bisque will have pre-sigged pots.

Also, am I correct in thinking that because FeCl3 is acidic it will
deflocculate a clay sollution? Will the iron then precipitate out if
the pH is then returned to neutral after settling? Can this type of
deflocculant interfere with others such as sodium silicate? Again,
spitballing.

For those of you who might answer, be gentle.

--
Taylor, in Rockport TX
http://wirerabbit.blogspot.com
http://wirerabbitpots.blogspot.com
http://www.flickr.com/photos/wirerabbit/

Gary Holt on tue 23 jan 07


Taylor - I can only answer your question about ferric chloride
affecting the surface of the clay... don't know anything about
it's deflocculating properties.

It will react with water, whether the water is in the unfired=20
clay body, or the raw terra sig, and as you've found out, the=20
reaction will dull the surface of a shined (or unshined) terra=20
sig permanently. You might try using iron sulfate instead of
the chloride. I know an equal amount of sulfate gives a=20
lighter color than the chloride, but perhaps a strong solution
of iron sulfate would come close to whatever color you're=20
trying to get from the chloride. It definitely won't corrupt=20
the surface as the chloride does. Hope this helps...

Gary
Gary Holt
Berkeley, CA.
www.garyholt.com


-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG]On Behalf Of Taylor
Hendrix
Sent: Tuesday, January 23, 2007 8:02 AM

I have not really been able to use my FeCl3 solution on my saggar pots
because I apply my sig to the bisqued pots, saggar, and then fire. I
have brushed FeCl3 onto bisqued ware alone but my tests last night
with raw sig and the ferric chloride were iffy. I could bring up a
shine with the terra sig but as soon as I brushed on the ferric
chloride I could not regain the shine. Oddly enough raw sig over FeCl3
would not bring up much of a shine either. Any thoughts? My next
bisque will have pre-sigged pots.

Vince Pitelka on wed 24 jan 07


> Also, am I correct in thinking that because FeCl3 is acidic it will
> deflocculate a clay sollution? Will the iron then precipitate out if
> the pH is then returned to neutral after settling? Can this type of
> deflocculant interfere with others such as sodium silicate? Again,
> spitballing.

Taylor -
Because FeCl3 is acidic it will flocculate a clay solution. Alkaline
(basic) additions will deflocculate. If you actually added FeCl3 to your
sig you would ruin it. Anything painted on over an unfired coat of sig is
going to ruin the shine. Apparently that's happening even when you paint
the FeCl3 on under the sig.

But I don't see a problem - the solution is so simple. Paint your sig on
and polish the pot before you bisque fire. You'll get a better surface bond
doing it that way. I'd avoid bisqueing any higher than cone 08.
Good luck -
- Vince

Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/

Ivor and Olive Lewis on wed 24 jan 07


Dear Taylor Hendrix,=20

As I understand things, mild acidity flocculates clay.

When Ferric Chloride dissolves in water it releases Hydrochloric acid =
and precipitates Ferric Hydroxide.

Best regards,

Ivor Lewis.
Redhill,
South Australia.

Taylor Hendrix on tue 30 jan 07


Hey Vince and Ivor,

Thanks for keeping me on my toes. If I had just thought about it a sec
I wold have realized I had the floc/defloc backwards (again!).

You didn't see a problem, Vince, because there was no stated problem
in this thread, so your eyesight checks out.

You and Lezlie Finet both are trying to get me to sig before I bisque.
It must be a conspiracy. Just fired off a load of 012 bisque and
several of the pieces were sigged raw. I LOVE the feeling and look of
raw sigged pots, Vince. Wish I could keep them that way. However, some
of my pieces did not like being sigged while bone dry. Just ask Lezlie
how many of my lid handles survived the sigging. (yeah, yeah, attach
them better, Lezlie).

Anyway, this is a great learning experience working with low fire
saggaring, and remember "Once you've had sig, you never renege."

Tay Tay, in Rock Rock

On 1/24/07, Vince Pitelka wrote:
...

> Taylor -
> Because FeCl3 is acidic it will flocculate a clay solution.

...

Donna Kat on wed 31 jan 07


On Tue, 30 Jan 2007 10:26:39 -0600, Taylor Hendrix
wrote:

I never heard or thought of doing terra sig on bisque! It is so, so,
so.... I just can't stretch my mind around it...

I have tried all sorts of methods of polishing terra sig and my favorite
is using a soft cloth just as it goes from wet to damp (dry enough that it
won't get damaged by touching it but wet enough that you can see a
difference in color from the dry. Put a cushion of some type in your lap
that will support the pot, paint a relatively small area, polish and go
the the next area. I put anywhere from 1 to 3 coats on (depending on
color and shine). The only difference between this and using a pebble,
spoon, etc. is that I don't get the indentations. When I was first shown
this method I could not believe it could possibly work.

Donna

>Hey Vince and Ivor,
>
>Thanks for keeping me on my toes. If I had just thought about it a sec
>I wold have realized I had the floc/defloc backwards (again!).
>
>You didn't see a problem, Vince, because there was no stated problem
>in this thread, so your eyesight checks out.
>
>You and Lezlie Finet both are trying to get me to sig before I bisque.
>It must be a conspiracy. Just fired off a load of 012 bisque and
>several of the pieces were sigged raw. I LOVE the feeling and look of
>raw sigged pots, Vince. Wish I could keep them that way. However, some
>of my pieces did not like being sigged while bone dry. Just ask Lezlie
>how many of my lid handles survived the sigging. (yeah, yeah, attach
>them better, Lezlie).
>
>Anyway, this is a great learni