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Kiln Wash: Everything You Need to Know & How to Use it

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by David Miller  • Updated: September 26th, 2022  •  8 min read    Pottery Guides » Pottery Kilns

Kiln wash is a very useful technique to ensure that an artist’s work and their ceramic kilns and equipment are protected from damage during a kiln fire, even though a successful kiln firing is based on a number of different conditions.

You might be wondering what kiln wash is and why you would need it in the first place.

This article will explain all you need to know about kiln wash, including why you should use it, how to properly mix it, and how to apply it.

Whether you’re a ceramicist, a beginner hobbyist, or a professional, knowing the qualities of kiln wash and the rules for its application are vital for you to produce your finest work and can help you avoid difficulties that could end up costing you a lot of money.

What is Kiln Wash?

Kiln wash is the method that is recommended for use by beginners since it is the safest and most effective way to protect expensive kiln shelves.

Kiln wash acts as a barrier that prevents fired glazed ware from coming into contact with the kiln shelves, preserving the integrity of the kiln shelves. To get the paint-like consistency, powdered refractory materials are combined with water in the appropriate proportions.

If a clay body fluxes too much or a glaze unexpectedly spills off a pot onto a kiln-washed shelf, the ware will often only attach to the wash and not to the shelf.

Most potters use kiln wash to protect their shelves from accidental glaze contact or prevent particular clay bodies from bonding with the shelves.

Kiln wash is necessary even for potters who wipe the glaze off the bottom of unwaxed pots because glaze soaks into the pores of bisqued ware and then melts during the firing process.

Should I Make my Own or Use a Premix?

Because there are so many different materials, kilns, and firing methods, there is no one kiln wash that is perfect for everyone. If you want to make your own recipe, ceramic-materials providers sell the dry ingredients you need, but they also sell premixed kiln wash that can either be in powder or liquid form.

Our Top Pick
Amaco Kiln Wash

Amaco Kiln Wash makes it easy to clean up glaze drips and keeps damage from happening. Before firing, mix with water and paint on the shelves and bottom of the kiln.

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How to Apply Kiln Wash

Kiln wash can be applied using a paintbrush of any width, a paint roller, or even by spraying it on. The coats should be very thin, and you should apply only the amount of wash necessary to cover the surface. It is important to be careful not to get any wash on the bottom or the sides of the shelf.

Kiln wash will cling more effectively to a new shelf if it is initially submerged in water, even though it takes longer to dry using this procedure. The coating forms stronger bonds because it penetrates more deeply into the surface.

How to Remove Kiln Wash From Shelves

After firing a glaze kiln, it should not be too difficult to remove most pots that have been stuck or glaze drips from a shelf that has been kiln-washed. Many potters remove the more difficult drips off their work with a hammer and a masonry chisel. The chisel is positioned at a low angle to the shelf, and the potter taps lightly yet firmly to remove the glaze.

Although some potters choose to use a power grinder to remove imperfections and old kiln wash from shelves, it is important to remember that this process can be highly risky due to the dust it creates. You should take caution to operate in a place with adequate ventilation, always use a dust mask, or, if possible, dampen the surface of the shelf to reduce the amount of dust produced.

Some potters scrape off the kiln wash after each firing and then reapply it, while others apply it on an as-needed basis solely to the portions that have been damaged (such as being chipped or becoming thin).

Make use of the approach that is most convenient for you. Use a hard brick to level the old wash in the areas where the kiln wash has chipped off, then fill any imperfections with thick wash and rub the surface level once more.

Is Kiln Wash Necessary?

Some potters don’t bother with the kiln wash because they only employ glazes that are known to be safe, such as those that don’t run or flake or they don’t use glazes at all. When an uncertain glaze is used, the finished item is set atop a shard of a shattered shelf or a tile that has been left blank.

When potters do not use kiln wash, they are free to often turn over shelves without worrying about any leftover kiln wash falling on the ware below.

Some potters prepare their shelves for each firing by dusting them with alumina hydrate, kaolin, sand, or grog, and then they recycle this material when the firing is complete. You must take extra care to prevent these particles from falling onto the items below.

Kiln Wash Vs Kiln Paper

Kiln paper is the equivalent of the parchment paper that you put on your favourite roasting pan. Kiln wash is more long-lasting than kiln paper for many of the same reasons that a non-stick pan coating is more durable than parchment paper. This analogy works well on many different levels.

Nevertheless, they both accomplish what they set out to do. Kiln paper is a straightforward and sophisticated method for constructing a protective barrier in kilns with firing temperatures of 1600 degrees Fahrenheit or lower. When compared to kiln wash, they can be discarded and reused with ease, which is the best part about them.

Our Top Pick
Fuseworks Fiber Shelf Paper

This paper can be cut into any size or shape, making it perfect for use as a smooth separator on a flat kiln shelf. The Fuseworks Fiber Shelf Paper can handle temperatures up to 2300°F (1260°C).

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Kiln wash may be a more straightforward product, but it is just unable to compete with the high melting point and extended shelf life of kiln wash. Use kiln wash if you need something that will remain in place over a large number of firings at a high temperature and is easy to break down.

Kiln paper should be utilised while working in a smaller studio that conducts firings at lower temperatures less frequently. Kiln wash, if used in an excessive amount, might destroy electric kilns; therefore, it should be done sparingly or kiln paper should be used. This is another cautionary note that should be mentioned.

Kiln Wash Recipes

There are a great number of different recipes for kiln wash available. Every option has both positive and negative aspects. Below we have listed the ones that are not only the simplest to make but also produce the highest quality results and may be utilized for an extended period of time.

Basic Kiln Wash

EPK Kaolin 50 %
Silica (Flint) 50 %
Total 100%

This is an effective kiln wash for electric firings in the lower and middle ranges. The only issue is that it is composed of silica, which is a component that can produce glass. Therefore, if a significant amount of glaze were to fall onto the shelf, it would cause the silica in the kiln wash to melt, which would result in the formation of a glaze on the shelf.

In addition, the act of scraping your shelves to clean them generates a significant amount of silica dust, which is a substance that is known to cause cancer. Therefore, adding silica to your kiln wash might not always be the most effective strategy.

No-Crack Kiln Wash

Alumina Hydrate 50%
Calcined EPK Kaolin 25%
EPK Kaolin 25%
Total 100%

This recipe is perfect for use in studios with low, medium, and high fire capabilities. It is essential not to use a kiln wash that contains a great deal of silica when working in high fire since silica will combine with ceramic when the temperature is high enough.

This recipe is also successful when used to make wadding. You can do this by making a clay mixture that you may use to support pots or level kiln shelves. You need to mix up a batch and add around 25 percent water to it. However, a mixture of 50 percent normal kaolin and 50 percent alumina hydrate would result in a slightly less expensive product.

Common Kiln Wash Issues

Here are a few extra tips to keep in mind when you’re cleaning your pottery wheels:

  • You can build kiln shelves from a wide variety of materials (such as silicon carbide and mullite), which means that a kiln wash that is effective on one type of shelf might not be effective on another type of shelf.
  • Because of the fluxing effect in either the materials or the atmosphere, you cannot use washes containing silica on shelves for firing porcelain or in salt or soda kilns.
  • If the kiln wash tends to settle out quickly, adding between one and two percent bentonite to the dry mixture can help keep the wash suspended.
  • Before firing, some kilns wash the shelf to remove cracks and chips from the surface. Adding 0.05 percent of powdered CMC gum to the dry mixture will stop this from happening.
  • When shelves warp, it is sometimes possible to flatten them by firing them upside down; however, before doing so, you must remove all buildup from the kiln wash to avoid flakes contaminating pieces that have been glazed.

Conclusion

Because kiln wash is such a common ingredient in the ceramics studio, we tend to take it for granted when we use it. Potters put a significant amount of money into their kiln shelves, yet combining two scoops of kaolin and alumina as a protective coating doesn’t take more than a few minutes.

They also spend countless hours creating and perfecting their work, only to endure unnecessary breakage and loss of pots because they simply aren’t aware that a kiln wash doesn’t have to crack.

If we take the time to educate ourselves on the components we use, there is a wide variety of recipes from which to choose and many solutions to the most common of problems.

Featured image courtesy of the Ceramic Arts Network

David Miller is an amateur potter that started as a hobby nearly 7 years ago. His mission is to share tips, tools and ideas he has learnt along the way. When he's not in the office, he can typically be found in his studio, a.k.a. his shed, creating, experimenting, and generally making a mess.
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