Dave Finkelnburg on mon 8 jun 09
Hi John,=3D0A=3DA0=3DA0=3DA0 You have it right, as does Ivor, that the acid=
floccul=3D
ates clay systems...though=3DA0not all systems.=3DA0 Bases are flocculants =
in a=3D
lumina systems, for example.=3DA0 This seems like a=3DA0fine point, but it =
help=3D
s to understand that not all systems are the same.=3DA0 =3D0A=3DA0=3DA0=3DA=
0 Weak org=3D
anic acids "age" in a suspension possibly due to decomposition but more lik=
=3D
ely because of the same reason as inorganic acids--they are neutralized by =
=3D
leaching salts like Na+ coming out of frits or feldspars or by=3DA0other ac=
id=3D
-base reactions.=3DA0 This stands to reason....the more a glaze or clay bod=
y=3D
=3DA0has salts tending to deflocculate it=3DA0the more it needs a flocculan=
t.=3D
=3DA0 This is why physical (clay, bentonite) suspension is usually better t=
ha=3D
n chemical suspension where we tend to store batches of glaze or clay=3DA0f=
or=3D
a long time.=3D0A=3DA0=3DA0=3DA0=3DA0 Good potting,=3D0A=3DA0=3DA0=3DA0=3D=
A0=3DA0=3DA0=3DA0=3DA0=3DA0=3DA0=3D
Dave Finkelnburg=3D0A=3D0A--- On Mon, 6/8/09, John Hesselberth rth@=3D
GMAIL.COM> wrote:=3D0A=3D0AFrom: John Hesselberth =
=3D0AS=3D
ubject: Re: Vinegar . was Re: stinky paper clay=3D0ATo: Clayart@LSV.CERAMIC=
S.=3D
ORG=3D0ADate: Monday, June 8, 2009, 9:49 AM=3D0A=3D0A=3D0AOn Jun 8, 2009, a=
t 9:01 A=3D
M, William & Susan Schran User wrote:=3D0A> I always thought vinegar defloc=
cu=3D
lated clay. That's why we use it to=3D0A> apply=3D0A> handles or add it to =
slur=3D
ry to join clay.=3D0A=3D0AHi Bill,=3D0AAcids are flocculents. For example y=
ou can=3D
use a little vinegar as a=3D0Aquick fix for a rapidly settling glaze. It d=
oe=3D
sn't last because it=3D0Adoes get eaten by bugs or whatever when it is very=
d=3D
ilute.=3D0ARegards,=3D0AJohn=3D0A=3D0A=3D0A
Vince Pitelka on mon 8 jun 09
Bill Schran wrote:
"He allows his trimming scraps to dry out, then wets, blunges with mixer an=
d
dries to moist plastic state. I had asked him about the suggestion of addin=
g
vinegar to slurry to prevent areas of dry materials to form. He responded
that if the porcelain separated it is deflocculated and one should never ad=
d
vinegar to porcelain as that deflocculates the clay. If the porcelain is
deflocculated one should add Epsom salts."
Bill -
As you may realize by now, Tom Turner was incorrect above. He is a
wonderful potter, but vinegar, like Epsom salts, is a flocculant. As John
Hesselberth pointed out, the disadvantage of vinegar as a flocculant is tha=
t
in low concentrations it gets consumed by bacteria. When I have made a
quantity of slabs and am keeping them on canvas, I spray them to keep them
moist for soft-slab work, and my spray bottles always contain some vinegar.
The canvas will start to mold very quickly if I do not use the slabs within
a few days. That does not happen with a weak Epsom salt solution.
You wrote:
"He keeps a squeeze bottle full of deflocculated porcelain for joining
handles and other appendages. He adds Calgon water softener, but said sodiu=
m
silicate or Darvan would also work."
Calgon, Darvan, sodium silicate, and soda ash (sodium carbonate) are all
commonly-used deflocculants. As far as I know, alkaline salts deflocculate=
,
and acids flocculate.
- Vince
ivor & olive lewis on tue 9 jun 09
I have replied to William Schran off list since he sent his original mail t=
o
me.
But to clear things up...... Vinegar, a weak acid assists in the
flocculation of clay. Last year I did a series of trials which tested the
ability of some salts to change a liquid deflocculated slip into a plastic
mass. This was done using N/10 solutions of salts that I could obtain and
Porcelain Slip, Kaolin Slip and Ball Clay slips of the same clay mass per
unit volume of water.
From my results I concluded that salts which gave the greatest Cation
(Positive charge)concentration in aqueous solutions were best at causing
slip to thicken into a plastic mass.
Using this information I would consider Citric acid to be a substance that
would promote a high level of flocculation, greater than that of Vinegar.
Best regards.
Ivor Lewis,
Redhill,
South Australia
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