Pottery Tips and Techniques
What Is Raku?Raku is a pottery technique that has it's origins in 16th century Japan.
We are pretty sure that it was developed by Korean pottery workers under Japanese rule but the exact way that it was developed and how it was discovered is a mystery.
The raku technique, like other pottery techniques such as salt glazing and pit firing is about the firing process, but association with raku often goes much deeper into its philosophy, roots and cultural significance.
Raku from across the pond and the western version are similar in many ways but there are also some significant differences.
Just about all other types of pottery are loaded into a cold kiln, where the firing proceeds slowly until the desired temperature is reached.
This firing cycle may take anywhere from 8 to 24 hours or even longer.
When the kiln has reached the right temperature, which is generally determined through the use of pyrometric cones, it is shut off and allowed to cool enough to remove the pottery or ceramics using bare, or lightly gloved hands.
The cooling cycle may last from 12 to 24 hours or longer.
The pottery is considered finished when it is taken from the kiln.
In raku, the pottery may be loaded into a cold kiln, but are often preheated and loaded into a hot kiln.
Who Invented Raku?Paul Soldner introduced the new method of firing and was one of a few responsible for making raku popular in this country beginning in the 1950's.
What Is The Difference Between Pit, Sawdust, Smoke firing and Raku?These types of firings are often confused with each other because they do share some similar characteristics.
Raku pottery is fired in a more or less conventional type kiln where glaze technology is understood and used.
The others are forms of primitive firing where temperatures reached are generally lower and glazes are not commonly used.
In primitive firings, the kiln may consist of a simple hole in the ground or a pit.
Do I Have To Bisque Fire First?Raku firing greenware is a sure way to line the bottom of your kiln with broken pottery pieces!
Always bisque fire your pottery to at least Cone 08 before glazing and raku firing.
Can Raku Be Used For Functional Use?The handed down use of raku pottery in the Japanese tea ceremony has contributed to the confusion about the functional use of raku.
With very few exceptions, all raku fired pottery is fragile, porous and generally unsuitable for functional use.
Unless such fragile pottery is treated after firing with a non-glaze material, such as a polyurethane or acrylic sealer or an oil of some kind, the pots will soak up water and eventually breakdown.
You should treat raku as decorative.
The occasional use of raku in a functional setting is OK, but keep in mind that the glaze is soft and can be easily chipped and swallowed.
Food use and storage is not recommended for Raku Fired Pottery.
The fragility of the pottery also causes the reliability of handles and other attachments to be extremely questionable.
Is There A Special Raku Clay?Raku clay is any clay that can be successfully raku fired.
That includes just about any type of clay out there!
A clay suitable for raku needs to contain a lot of fireclay and similar refractory materials so that it can withstand the sudden heat shock of the raku process.
This includes most stock stoneware clays.
The clay does not have to be loaded with coarse grog but it does have to be open enough to expand and contract without cracking.
Most clay suppliers can help you choose the right clay body.
The other characteristics that you are looking for are your personal ones such as plasticity, color, texture and so forth.
Nothing needs to be sacrificed in order to have a good, reliable raku clay.
What is a raku glaze?Similar to the question of raku clays is the answer to this question.
Any glaze that you can successfully raku fire is a raku glaze.
The most important factors in identifying raku glazes is the temperature at which they mature, how you plan on using them, and what kind of effects you are looking for.
You must also keep in mind that if you are using a variety of glazes on the same pot or in the same kiln load, unless you know that they will all mature to your satisfaction at around the same temperature, you will be faced with varying degrees of maturity.
Now, just because a glaze is formulated to fire at a temperature higher than your usual range doesn't mean that you should eliminate that glaze from your pallet.
Experiment with your glazes to achieve a variety of surface effects from dry textures to surfaces with a high gloss.
Don't limit yourself to homemade or personal glazes either.
Try low fire commercial glazes for some unusual results.
Which Cones Do I Use In Raku?The only cones that should be used near a raku kiln are ice cream cones!
Because of the fast firing, varying atmosphere, multiple loads and other factors, pyrometric cones are generally poor indicators of heat and temperature so they are not used.
Most raku pottery workers fire their pottery using the actual glaze melt as the visual indicator of maturity.
Some pottery workers, do use pyrometers or cones to warn of coming glaze maturity and then check the pottery visually through the peepholes.
Some temperatures of raku depends on the glazes that you are using.
Most raku is fired in the range of cone 010 to 06.
You must remember though, that you, as the maker of the pots are the final expert on whether a glaze is mature, underfired or overfired.
If a glaze is not glossy enough, doesn't have the expected crackles or metallic effects and doesn't exhibit any other characteristic that you find desirable, you need to adjust the firing.
What Can I Do If I Don't Get Bright Metallic Effects Or Crackle?
Assuming you are using the correct glazes, both metallic effects and dark crackle lines are a result of firing the glazes to their maximum maturity followed by a fast after firing reduction technique.
You must quickly get your pottery from the kiln to the reduction container and covered before the pot has a chance to cool too much, otherwise the after firing reduction will not be effective.
Pronounced crackle effects are also often dependent on a thick application of glaze.
Bright Metallic Effects And No Colorful Glaze Effects.This is the exact opposite of the question and problem above.
Brighter colors need a degree of after firing oxidation in order to develop.
There are several ways to achieve this.
When you remove the pottery from the kiln, spray the areas with water where you would like more color to develop before placing the pottery in the reduction container.
This will oxidize and cool the glaze.
Another method is to hold the pottery in the air for 10 to 30 seconds before reducing the pottery.
Allow the combustible material to ignite and cover the container only after flames have clearly developed.
Other pottery workers will uncover the reduction container after a short time allowing the material to ignite again while fanning the pottery.
Using these and other similar techniques you will learn how to control the amount of metallic and colorful effects on your pottery as well as gray to black unglazed areas.
Can I Preheat My Pottery In The Kiln As It Is Warming Up?
This question shows a common misunderstanding about the raku process.
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Handmade pottery can be a very gratifying hobby that produces fun and satisfying results. For many people it's an enjoyable release that is created by working an inanimate mound of clay into a beautiful work of art that you made through your artistic abilities.
The best way of starting out is to take a few lessons. You will probably waste quite a bit in materials when you first get started. Figuring out how to truly make handmade pottery correctly and shape into what you want it to be can be quite an ordeal. The different tools that a normal shop will have can be fun to try. You will soon see which ones you like to use the most and then when you are ready you will know which ones to buy.
With the help of the internet, you can now purchase most if not all of your ceramic and pottery tools and supplies online. We are located far from any well supplied dealers and yet working with reliable ceramic and pottery suppliers online has allowed us to recieve most of our orders within a timely manner.
When you get all set up, just enjoy the hobby and have fun at it. Some people get pretty serious and start selling their creations at craft fairs and small stores, but others just like to create items for themselves, relatives, and friends. Whichever kind of handmade pottery you desire to endeavor, enjoy the hobby and have fun doing it.
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