Laura Conley on tue 16 jun 98
I am confused. If vinegar is a flocculant, doesn't that mean that adding it
to slip will cause MORE liquid to evaporate and more shrinkage to occur than
if one added the same amount of water? My understanding (which may indeed
be incorrect) is that a flocculant causes the clay particles to
aggregate/stick to each other more and a deflocculant causes the clay
particles to repel each other. If this is true, wouldn't one need to add
more flocculant than deflocculant to the same amount of clay to make slip
of the same consistency???? I realize that vinegar works for everyone - I
just want to understand the theory. I have had success with using soda
silicate in the slip for repairs. I stubbornly haven't used vinegar because
I don't understand why it works (now this is a good examply of technological
knowledge, and lack thereof, getting in one's way).
TIA,
Laura Conley
Boulder, CO
Janet H Walker wrote:
> ----------------------------Original message----------------------------
> Vinegar is a flocculant. (Read in Hamer or other technical sources
> about what that means.) It thickens up a mixture with clay in it.
> When you make a slip by mixing vinegar into dry powdered clay, it is
> a different kind of slip than the one you make with water. The clay
> doesn't shrink as much as the vinegar dries.
>
> In my experience, this may or may not be a good thing. If you have
> a piece that is cracking as it dries, you can clear out the crack
> with a knife or tool and then "spackle" it full of vinegar slip.
> Keep adding and compressing that and your crack will not come back
> after the piece is finally dry.
>
> If, however, you use vinegar in place of slip when you are constructing
> handbuilt things, it might or might not work. I have several big pieces
> in my bone pile to remind me "don't do that". I constructed a piece
> using vinegar and my usual constrcution techniques. The piece cam
> apart along the seams in the glaze firing. Quite fascinating really.
> This particular clay doesn't wet easily and so i think that the vinegar
> just didn't do a good enough job of getting a homogeneous blend along
> the seam.
>
> So the answer is "it depends". By all means, have fun.
> Jan Walker
> Cambridge MA USA
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