Tuesday, March 17, 2009

Firing temperatures and what they mean

Orton Standard cones were created by the English. Each cone number coresponds to a temperature. It starts with cone 022 and counts backwards to cone 01 and then counts forward again from cone 1 to cone 15.
cone 022 - Fahrenheit 1121...................... the clay dehydrates.
cone 018 - Fahrenheit 1328.......................over glaze or enamels mature
Cone 015 - Fahrenheit 1481......................glass slumps
Cone 012 - Fahrenheit 1607......................luster glazes mature
cone 09 - Fahrenheit 1706......................low fire lead glazes mature
cone 07 - Fahrenheit 1815......................low fire earthenware glazes mature
cone 06 - Fahrenheit 1845...................... native and red clays mature, raku
cone 02 - Fahrenheit 2055......................buff colored clays mature, high fired earthenware
cone 2 - Fahrenheit 2130.....................soft stoneware vitrifies
cone 4 - Fahrenheit 2174......................china glazes
cone 6 - Fahrenheit 2245......................soft feldspar glazes mature
cone 8 - Fahrenheit 2300.....................Stoneware clay matures, Salt glazes
cone 9 - Fahrenheit 2345......................Stoneware glazes
cone 10 - Fahrenheit 2381...................... Hard stoneware
cone 11 - Fahrenheit 2417......................porcelain begins to vitrify
cone 13 - Fahrenheit 2465......................Porcelain matures, porcelain glazes mature

Monday, February 2, 2009

Raku 101

I was first introduced to the process known as Raku in 1976. I was in high school. My teacher took us out into the parking lot and had us set pots on fire using a kiln made out of bricks and a propane tank. It was love at first sight!
Raku has been done for 3000 years starting in Japan. However, it all changed in the 1950's or there abouts. I don't remember the exact date. Anyway, Paul Soldner was the first to take the pots out of the kiln and place them into some sort of combustible material and then smoked. He then washed them in cold water while they were still hot.
OK, since then people have been playing around with combustibles. The popular ones are saw dust - very dangerous if the area is prone to wind. News paper - gets a good flame but does not add any chemical to the glaze. Straw, leaves, or vegetable skins - leaves marks on the pot that can be a nice decoration. Wood chips - can add chemical like cedar resin, but hard to find. Magazines - shinny surface of paper is EPK so can enhance glaze color. Some people spay alcohol - interesting effects with glaze color. I have also seen people use a hand held torch latter to change the glaze color in a certain area of the pot.
Also how the combustibles are put into the metal garbage can is called the nest. You want the pot to sink down into the combustibles. So that it flames right away on as much surface as possible.
OH, before I forget, advice a heard from a teacher once. When you are ready to take the pots out of the kiln ------WAIT. The shinny surface from the glaze can only get more shinny. Then its time to set them on fire. The longer the pots are in the kiln the more mature the glaze becomes, the prettier the color.
As for washing the pots in cold water after being taken out of the smoker - DON'T!!!!!!!!!!
You are asking for cracks!!!!!Let the pots cool for awhile first. Raku already breaks the rules about clay. The pots are not supposed to be thermal shocked. Yet that is exactly what is happening to them. 15 - 20 min. in the kiln, 15 - 20 min in the smoker. All throwing mistakes will show up in technicolor. All bad craftsmanship in hand building will also be shown to you. Why ask for more cracks?
Once the pots are completely cooled then scrub them to get off the ash and carbon. Let them dry, then spray them with anything that will seal them. There are a variety of ways to seal them like lacquer, polyurethane, grout sealer, or floor wax. These are necessary so that the pots are functional.
The ancient way to Raku was the quick fire without the second stage of setting them on fire. I have experimated with this. With some vey interesting results. The pots still need to be sealed.
As for the glaze formula
Gerstly Borate 80%...................................I have used Nephline Synite instead.
Cornwall Stone 20%
then colorants - like copper carbonate, Iron, cobalt
I have also tried mason stains
I have even experimented with cone 05 glazes, they mature at the same temp.
The best part about Raku glazes is that the mixing does not have to be as exact. Also don't need to worry about seiving the glaze.
Most art schools and universities only raku once a semester. This is to bad. There is alot to play with here.
By the way the vase above is called "The Dancing Ladies"
She is one of my signiture pots.
www.hstoneware.etsy.com for more info.

Tuesday, January 20, 2009

Prayer Bowl

Give wings to your prayer
While you release your cares
Look within the small bowl
To remember angels love
And let it fill your soul.

Say a prayer
Write hopes dreams or sorrows on blank white paper
Fold and place in your bowl
Burn the paper
Say Thank You
Allow the miracle to happen

The above words are on a card that comes with the bowl.

This Prayer Bowl is one of my claims to fame. Its been seen in catalogs like Femail Creations, Heartbeats and Abbey Blessings. It has been sold to churches, women's groups, and various recovery groups nation wide.

I created the bowl in homage to my grandmother. I was her care giver for the last three years of her life. I watched her slip away from me as she battled Alzheimer's. Nine months before her passing she started to speak of going upstairs and the beautiful music she could hear from there. She kept looking for the door to take her upstairs.

The experience touched my life. I walked back into my studio after her death and had to create a piece in her honor. I come up with the bowl. It is based on the Japanese tea bowl and the Tibetan begging bowl. It is Raku fired because the process is transformation through fire like a phoenix rising from the ashes. The three angels and the instructions touch on many religions world wide. The purpose of the bowl is promote the universal language of love and understanding. A way to speak to upstairs!!!

If interested in getting one -
www.hstoneware.etsy.com is my store

Thursday, January 15, 2009

In the flames

I do these in an electric kiln. Most people use a Raku kiln, but that means cracks when any breeze hits the pots. So I build the shelves up to the top of the kiln. Turn the kiln on to high for about an hour then turn it off and start adding feathers, cat hair, dog hair, snake shed, leaves and the normal horse hair. I have even used my own hair. You only have about 3 min. to work in. Then its to cool. The smell is TERRIBLE!!!!
After the pot have cooled off then they can be washed. Then its time for the acrylic spray to protect the surface.

Tuesday, January 13, 2009

Why pottery is in a blog.....

I have been a full time potter for going on twenty years. Selling in craft shows, galleries and catalogs. When I am out talking to my customers I spend about half my time explaining how I do my craft.
The history of Raku.
What is the best burning material?
What is stoneware and can it be microwaved?
How hot does a kiln get?
Is there any lead in my glazes?
There is so much to the world of clay. It is the study of not only the manipulation of the clay, but also chemistry, geology, structural physics and history. I do not know it all and am always learning more everyday. Yet I will pass on all the information as I get it.