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kenny on slip

updated mon 8 feb 10


lili krakowski on sun 7 feb 10

Oh, Susan! Poor you!

You say you can't afford a commercial slip mixer! Who can, and why =3D
should anyone? You tell us "I can't afford a proper slip mixer, so I'm =
using a 33 gallon garbage bin on wheels. I tried using a paint mixer on =3D
my drill (HA!) which broke in about 5
minutes. Then I rented a bigger better drill and tried to use a mortar
mixing attachment. Well, that worked alright until the motor started
smoking, so I stopped that quickly. Then I rented a 3/4" drill (two, or
three handed [word not clear]...about the biggest you can get) with one =3D
speed which was
so strong it whipped all kinds of air into the batch...."

You spent a lot of time and money, broke several costly tools, all in =3D
pursuit of something you could have achieved with a little more =3D
--forgive me--foresight and patience.

1. WHY did you go out and try a new recipe in this huge batch? Could =3D
you not have made tiny batches and tested? I assume this is for slip =3D
casting--but could you not make several small molds to test slipcasting =3D
slip in? Kenny warns about being very careful with deflocculants--a =3D
little goes a long way, it quickly becomes too much.

2. All the books tell one to add the dry stuff to the water...So? I am =3D
all for innovation--but start small...

3. Taking Marcia Selsor's hint: =3D20

I found my copy of Kenny "The Complete Book of Pottery Making" (second =3D
The ends of several of my typing fingers are cracked (duh!) so I will =3D
condense The Message:
He says that when 1000gms of dry clay are mixed with 400 gms of water, =3D
you get a thick sticky mass. Add a few drops of sodium silicate and you =
get a smoothcreamy liquid...a deflocculated slip. [This has to do with =3D
electrolytes, which I do not,never have, understand)

He does not mention Darvan, about which I know zip...I do not know why =3D
both sodium silicate and D, are needed) but Kenny DOES say that some =3D
clays require more than one deflocculant and some cannot be d/f at all. =
And he warns to be careful as too much d/f will"reverse the [desired] =3D
process and cause the slip to jell into a semi solid mass."

He gives several suggestions for testing small batches...

`As to aging:

You should let the slip age slightly- 3 or 4 days. Keep it covered, =3D
stir often. Screen though a 40-60 mesh sieve every time you cast..

4. Meanwhile here is my patented, trademarked, copyrighted, secret All =3D
Purpose Studio Life Saver.

Get a "replacement" bucket for a wheelbarrow (you can use and actual =3D
wheelbarrow, if you steady it) or a builder's mixing trough--a thing of =3D
heavy black plastic that looks like a kitty litter pan for a lion.

Get some hardware cloth 1/2" and 1/4" and some fiberglass mosquito =3D
netting. Cut these to size to fit over the pan, with about 2" leeway =3D
all around, as it will tend to move when you use it.
Make a wooden frame for each thickness. (3 frames).

You place the appropriate mesh-size screen on the tub, and pour your =3D
slip/slurry through, by the gallon or two gallon bucket. Use some sort =3D
of spatula or a scrub brush to work the liquid through.

This allows one to sieve slurry, reclaim, slip that has lumps in it, and =
so on. It is quick and easy, much easier than standing there struggling =
with a large drill, and mixes the slip thoroughly.

A 33 gallon pail divided in 2 gallons will take like 45 minutes to =3D
screen. And yes, you will need a second garbage can to pour the sieved, =
processed stuff into.

If there is need one then proceeds to fine sieves.

And again. The Kenny book is available, for $2 up, at a number of used =
book dealers on the Internet. The shipping probably would be $5--so =3D
having that info on hand would have saved you all that expense and =3D
sorrow. I simply cannot recommend clay books on hand enough.

I wish you success.