2/5/10 - 3/15/10

The Process of Making Pottery

Part II  - The Glaze 

Part I - The Clay           Part III - the Fire

When I'm throwing I'm thinking about form, not glazes

I keep these little samples around to help organize  my thoughts:

 I start to arrange the pots in little piles  using ware boards  - (right) 1" X 12" or 8" or 6"
The terra cotta pot on the left is for drying trimmings to be slaked and recycled

At some point one must mix the glazes

Before we go from clay to glazes we should address the idea of clay IN glazes.
Many recipes you will see contain 25 percent clay
This has many uses - keeps the glaze from "panning" AKA turning into a rock at the bottom of the bucket with water on top.
It adheres and coheres the glaze and makes the glazed pot easier to handle and not have the glaze flake off.
More on the subject later
(Google thixotropic in another window)

I do the measuring in front of an exhaust hood/booth to minimize dust
The material, here G200, goes from the bucket to the scale then into the water and any dust made goes out the fan.

You have to pay attention because it's mind-numbingly boring and if you daydream you may forget if you put in two or three measures of an ingredient.

It's pretty much basic mathematics to mix up a 1000g batch of glaze
The scale will only hold 610g at a time, max - so any component that adds up to more than that will need to be separated into portions.

For instance, my temmoku recipe calls for  1402g of G200 Feldspar per 2000g batch
So I add 500g, 500g, then 402g

Tony Hansen's Digitalfire Software is a whole education in glazing
It will store your recipes in a data base print them out for use, and he has a wonderful online reference website that will answer most glaze questions.
If someone gives you a recipe that doesn't add up to 100% - the program will recalculate so it adds up to 1000 or 2000 gram batches

Always add powder to liquid

Just mix:

If it doesn't come into solution, pour the glaze back into the pan and mix again
Careful not to add too much water

After mixing I push it through a 60 mesh screen just to eliminate clumps, and impurities:

This is 6000 grams of glaze - a practical amount to be moving around in that great invention - the plastic bucket.
I mixed three bowls of 2000g each pictured above.

Some of the best glazes in history are the simplest with few ingredients

Rhodes 32 is a wonderful glaze with a soft  feel to it.
made with just these 4 materials : Potassium  Feldspar 48.9, Kaolin 25.1, Dolomite 22.5 and Whiting 3.5
( From Clay and Glazes for the Potter, 1957, Danial Rhodes , Chilton )

And Mel's favorite !

Here's a sample of Rhodes 32:

Pot by Rick Bonomo

If you want to mix up the classic Reitz Green, there are a few considerations

"It originally was a shino until
Pete Pinnell or someone tried it with cobalt and rutile", per clayart discussion cited above.
Don't you think Don Reitz was the one ?

You have to gather up a whole new pile of materials:

I think I want to add to this amount to make the dipping/pouring/glazing easier, so I'll add 2000 grams

Bentonite keeps this glaze from panning, see below.

The glaze itself needs to be applied thick - so you can't have too much water in the mix
Also, there is only 8% clay in it, so it is subject to panning

Therefore, I add 4% Bentonite, but there is a price - it clumps: big time
There are a number of ways of handling Bentonite - I just push it through the screen with the liquid glaze.
Then again "clumping" is why you add it - Bentonite is an ultra fine clay that helps to hold the other ingredients up in suspension

Kitchen tools have lots of uses in a pottery
Just like cookie icing - mm mm

Other glazes waiting to be used

Coleman Clear, Leach 4321, Coleman Vegas Purple, MacKenzie Shino, Cushing's Magic Black, Coleman's Non-Iron Celadon

The next step is to is to decide which glazes to wed to the form
They become one
I try to make little families of similar or complementary forms with the same glaze
Now this just looks to me like it should be a pile of Celadon.

The transparent Celadon will reveal the carvings and impressions underneath

The current undisputed Queen of Carving under Celadon is Elaine Coleman

To be Temmoku:

One of the interesting things about glazes is watching them "break" to a different color
Classic Temmokus break to a brown where the rim is thin or other thin spots
Also nicely accepts an iron oxide over glaze decoration
Most potters love this sort of thing - it goes back thousands of years to China before porcelain.

David's  Simply Red breaks to a nice gray over stoneware

This is Simply Red being mixed - the bentonite is slow to enter solution
The green powder is the copper carbonate that will provide the red color when reduced

I like the way Vegas Red breaks over a white slip

Before glazing  you may want to place under glaze stains
Below is copper carbonate under Leach 4321 

I use the Giffin Grip for under glaze banding:

Over glaze decorations can be done using oxides, stains or just another glaze
Below is a postcard from Sequoia Miller -a very fine potter


I usually apply Shino first:
I first check the supernatant

Since I haven't altered this bucket, since last use, I'll assume it is the right thickness without having to remove water from the top

Our friend the paint mixer and hard wired drill

Carefully - this can make a real mess:

Then run it through a screen, again

Shino is a stiff glaze - and bubbles will show on the pot after firing
It doesn't smooth over like some glazes

One of the things I do to make  Shino melt is to sprinkle screened hardwood ash, like a wood flame might

Do this under a hood - don't breathe in the  ash - it's like powdered Drano - very caustic

Now I know that this (Reitz) glaze must be applied thick and if you'll recall I added to this batch
And I added 4% bentonite so I'm going to guess that it has gelled it up enough that I don't need this water
So I'll remove water with a siphon

After applying the Reitz glaze I will also spray it on the other side of the shino and on top of the already glazed pots.

On the pots to get an extra nice thick coat of glaze

On the shino to make it melt like this:

My "fancy" sink got pressed into service, since the other room flooded on 3/14/10

Beware the steps of the Senate!

 Iron oxide decoration over Shino glaze, an old, old eastern tradition

Red iron oxide also makes a nice decoration over iron black Temmokus:

I've concluded that there  is good reason to work with this glaze last
And perhaps why some artists wear black.
It is just chock full of pigments to make it black:
Chrome Oxide, Iron Oxide, Cobalt Oxide, and Manganese Dioxide
You don't want to get this on your pretty white t-shirt

This is the Yin to translucent white Porcelain's Yang

But it finishes off the bottoms of this set which has had four previous applications:
Shino Glaze, Ash Sprinkle (right), Reitz Green Spray (left side), Iron Oxide decoration and now a Magic Black Bottom,
and of course under the glaze is the faceting and handle applications

They all look pretty boring with out the fire:

And I hose down the floor regularly - just to keep the dust under control

Now transport up to the kiln house on ware boards:

All safe inside the kiln house and ready for the fire:

Thus concludes part two of our series.

Click The Fire for the third installment

This firing scheduled for 3/20/10

Part I - The Clay              Part III - The Fire

Click here for pots from November, 14. 2009

Click here for pots from August 2009

Click here for pots from May 2008

Click here for pots from February 2008

Click here for pots made in 2007

Click here for pots made in 2005

Click here for Glaze Recipes

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