Techno Tips: Clay & Computers

To Flocculate or Deflocculate?

At first, I had a bit of difficulty remembering if Pm suppose to
flocculate or deflocculate... a glaze that 1s. After thinking about it, I try
to remember that “birds of a feather, flock together”. So to flocculate
a glaze 1s to make it come together, clump, gather, thicken, attract.

The opposite is to deflocculate or repel, spread, thin out, disperse
or run. With glazes, we usually want to flocculate and make the glaze
thicken and stay in suspension. Why?

* prevents the glaze from settling and turning into a rock at the
bottom of the bucket

* improves glaze application with a consistent thickness all over
* glazes resists running and dripping so you get a smooth layer

* helps the glaze dry faster on the pot

* helps the glaze adhere better

The easiest method of flocculating a glaze 1s to use a solution of
epsom salts. In a medium-sized jar, melt several tablespoons 1n hot
water. You can put in as much epsom salts as will dissolve but a 1 to 4
ratio is fine. You can use calctum chloride or murtatic acid but epsom
salts is by far the easiest and safest way to floc a glaze. You also need
some fine clay particles in your glaze for the epsom salts to work. If
there 1s little or no clay or gerstley borate in the glaze recipe, add a bit
of bentonite (up to 2%) and you’re good to go.

After mixing up a new bucket of glaze, you need to add the epsom
salt solution a teaspoon at a time. Stir after each teaspoon and you'll
see a thickening of the glaze right before your eyes. It doesn’t need
much, so don’t over do it or you'll end up with some inedible jello. An
over flocculated glaze can also crawl after application and crack/crawl
while drying.

It’s not often, but sometimes, there’s a need to deflocculate a glaze.
Why?

* helps the glaze to spread or run easily. (to paint designs on bisque
pots and not have the brush dry out and clump all the time)

* makes the glaze or clay settle to the bottom. (to make terra sigillata)

You can use calgon, sodium silicate, soda ash or sodium carbonate
to defloc a glaze. A solution can be prepared in a similar fashion as
epsom salts.

There are some additives that are commonly called for to improve
glazes but don’t actually flocculate a glaze. Ingredients like CMC,
glycerin, gum, macaloid and veegum make the water thicker and slicker
and have a slightly deflocculating quality. These ingredients improve
the painting qualities of a glaze and helps hardens the dried glaze layer
so that it can be handled more easily.

Hopefully, I remember and researched all this stuff correctly.
Perhaps these techno tidbits will help you understand how your glaze
goes onto vour pots and enable you to make the glaze do the things you

want it to. Don Jung

continued from page 7...
downloading the document.

The guild newsletter attachment will
probably be about 1MB in size and we'll
try to keep it close to 1 MB so it won't take
too long for those with dialup connections.
You should expect a 1MB attachment to
download with the following speeds:

Cable / DSL =< 10 seconds.
112 Kbps 40 — 60 seconds
56 Kbps 80 — 120 seconds
19.2 Kbps 2.5 — 3 minutes
9.6 Kbps 5 — 8 minutes

It would be advisable that you get at
least 56 Kbps (Kilo bits per second) dialup
speeds. In the last five years, most if not all
modems are capable of 56 Kbps speeds.
Please check your modem and with your
Internet Service Provider if this is not
the case.

Please help us get your email addresses
correct by sending a note to update your
membership information at:
membership@bcpotters.com or
communications@bcpotters.com..

Don Jung

—=Ec——ll rr — rrr EEE