Kiln shelves, sometimes called batts, refractory tiles, or plates, are basic kiln furniture that provides you with a flat surface to sit various projects that can be fired at one time. They come in a variety of shapes, sizes, designs, and materials.
Generally, kiln shelves are classified either by the materials that they are made of or by their design features. In this article, we will break down the basic types of kiln batts that you may encounter and describe what makes each special.
Different Types of Kiln Shelves
To start with, we will look at different types of kiln shelves as they are categorized by their design.
1. Plain Batts
Plain batts are the most commonly used and have been a mainstay of pottery and ceramic kilns for thousands of years. They are, in essence, just flat shelves that come in a variety of shapes, sizes, and materials.
If you buy a furniture set for your kiln, it will most likely come with both full and half shelves designed to fit your kiln and maximize its capacity.
2. Perforated Shelves
Perforated shelves help to reduce weight and maximize the firing efficiency in your kiln. They are sometimes manufactured using an extrusion method, but these are considered inferior to perforated shelves that have been cast.
Cast perforated shelves offer a smooth, sealed surface that reduces the need for wash and kiln dirt.
3. Extruded Shelves
When looked at from the side, extruded batts look much like like heavy-weight cardboard. They have a flat surface on the top and bottom and channels running through the middle. This design makes them stronger than other types of shelves without adding too much weight.
Generally used for heavier items, the best-extruded kiln shelves are ground after being fired to assure a smooth flat surface.
4. Cover Batts
Cover bates are thin sheets that are used to retain ceramic fibers in kiln walls and kiln car bases. They provide a rigid surface, protect the fine fibers used to insulate the kiln, and reduce kiln dirt.
5. Feature Batts
Feature shelves have either a saw-toothed or grooved top surface. These groves offer many advantages. Just a few include the grooves minimize the surface contact between the product being fired and the shelf, reducing sticking. They help to standardize spacing. Perhaps most importantly, their grooved surface helps reduce movement and prevent rounded surfaces from rolling on the shelf.
6. Cast Shelves
Smoother, harder, and more abrasion resistant than more traditionally manufactured batts, cast shelves reduce the need for kiln wash and reduce kiln dirt.
Cast shelves come in many different designs, including perforated, plain, and feature batts.
7. Discs and Tiles
You will most often find discs and tile shelves in commercial and industrial settings. Unlike other batts, they fit specific shapes or offer support to unique designs.
People also classify kiln shelves by the materials that they are made from. Here we look at some of the more common varieties that you are likely to encounter.
If you are wanting to fire at Cone 10 or above on a consistent basis, then thermal-lite shelves are what you need. Rated for Cone 16 use, they resist warping better than any other type of kiln shelf. As an added bonus, they are thinner and lighter than batts made of more traditional materials.
9. High-Alumina Ceramics
High-Alumina Ceramic shelves are more stabile and warp-resistant than traditional cordierite kiln shelves due to the high concentration of alumina in the clay. This also makes them lighter and less prone to chemical damage and staining.
10. Nitride Bonded Silicon Carbide
Nitride bonded silicon carbide kiln shelves weigh half as much as traditional clay or silicon carbide batts and are much stronger and thinner to maximize kiln area. Nitrogen is introduced during their manufacturing process, giving them a much denser and less porous finish. This, in turn, makes glaze less likely to bond with the shelf.
11. Oxide Bonded Kiln Shelves or Silicon Carbide Shelves
When most potters speak of silicon carbide shelves, they actually mean oxide bonded shelves. These are thicker than nitride bonded shelves but thinner than clay shelves. By the same token, they are less porous than standard clay batts making it easier to remove glaze runs but not as stain-resistant as oxide bonded.
12. Cordierite Kiln Shelves
Most people think of cordierite shelves as extruded shelves. Cordierite is the material that is most commonly used to make extruded shelves as it takes shape easily when pressed through a dye and holds its shape well through the firing process.
What is the difference between Kiln wash and shelf paper?
People consider kiln wash to be the best way to protect your shelves. It is a thin liquid primer that you apply to your batts that prevents the glaze from sticking. As an added bonus, kin wash also makes it easier to remove fired projects without the risk of chipping.
In contrast, Kiln shelf paper is mainly formulated for overglaze work and glass fusion. Unlike kiln wash, if kiln shelf paper is subjected to temperatures above 1600 degrees Fahrenheit, it will begin to curl and burn.
What is kiln wash made of?
The primary ingredients in kiln wash are:
- Alumina Hydrate
Other ingredients that are also used in some brands are:
- Ball Clay
- Calcined Kaolin
- EPK Kaolin
- Zirconium oxide
- Zirconium Silicate
In theory, you can mix your own kiln wash but considering its low price, it really isn’t worth the effort.