Kiln Wash Usage and Application Guide
Perhaps you’ve experienced the difficulty of scraping glaze off a kiln shelf when you’re done firing your pieces. Potters can apply either store-bought or homemade kiln wash in order to preserve their shelves. If you’re new to ceramics, however, you may be wondering: What is kiln wash?
Kiln Wash Is Made to Help Prevent Glaze Damage to A Kiln Shelf During the Firing Process
Kiln Wash Comes in A Liquid Or Powder Form And Is Applied Directly To A Kiln Shelf. After Applying Several Coats, Thin Dried Layers Are Formed to Protect Your Kiln Shelves from The Chance Of Glaze Sticking To Your Kiln Shelves
Kiln wash is an essential step and regular part of the process. If you don’t use Kiln Cookies to protect your shelves. Knowing how and when to apply kiln wash will save you from many tiresome hours of cleaning your kiln shelves and potentially save them from being ruined.
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What Does Kiln Wash Do?
Kiln wash essentially acts like a coat of oil or non-stick on a cooking pan. It creates a hardened, disposable surface for the excess glaze, which comes off without damaging the kiln shelf.
By using a combination of compounds with extraordinarily high melting points, such as silicon dioxide and aluminum oxide, kiln wash creates a protective layer that’ll remain unmelted even in the heat of the kiln, which ranges from 1100-2400°F (593.33-1315.56°C).
Why Is Kiln Wash Important?
If a piece is stuck to the kiln shelf after firing, it can be extremely difficult or even impossible to remove without causing damage either to the piece or the shelf. You can prevent this situation by applying kiln wash.
Kiln wash is an important step in the ceramics process because it prevents permanent damage to the kiln shelf. This greatly reduces the risk of the shelf being ruined during the removal of melted glaze off the shelf.
Even if you manage to extract a stuck or fused piece from the kiln shelf without ruining it. You’re still left with the task of grinding melted glaze off of the kiln shelf. Glaze, once it has been fired, is actually harder than the shelf itself. This makes it easy to cause accidental damage to the kiln shelf while you’re attempting to remove the glaze.
How To Apply Kiln Wash
A thin layer of Kiln Wash is applied to the Kiln Shelf in a liquid form with a brush or roller. One thin coat is applied in long even strokes. Allow the kiln wash to dry for at least an hour and apply another thin coat in the opposite direction. Then allow the kiln wash to dry completely before using. This helps to prevent the kiln wash from peeling off easily and flaking in the kiln during firing.
Here are a few steps you can follow for applying kiln wash to your kiln shelves:
- When handling Kiln wash in powdered form always wear a Dust Mask.
- Clean the Kiln shelf with a clean damp sponge before administering the kiln wash.
- Mix the Kiln Wash thoroughly prior to application. Ideally, the kiln wash should be the thickness and consistency of melted ice cream or half and half.
- Apply the kiln wash to shelves using a standard 2 to 3 inch paint brush or small roller. Apply a thin even coat and let dry for at least an hour. Once dry apply another thin even coat in the opposite direction and let dry throughly before using your shelves.
- Try to keep the kiln wash away from edges to prevent the kiln wash from flaking off onto your pottery during the firing. Once applied to the side of the shelf it becomes very hard to remove, but will flake off over time.
- Don’t apply the kiln wash on too thick. As it’ll make your job more difficult when it’s time to scrape the old kiln wash off and can cause your kiln wash to flake off during firing.
What Is Kiln Wash Made Of?
Most basic kiln washes are an even blend of 50% EPK Kaolin and 50% Silica, also known as flint. Some firing methods, however, require more specific kiln washes. Potters using salt, soda, or wood firing use kiln wash composed of kaolin, ball clay, and alumina hydrate.
This 1:1 ratio of kaolin and flint is suitable for gas and electric kilns but can’t be used for salt, soda, and wood firing. A ratio of 40% kaolin, 10% ball clay, 50% alumina hydrate should be used when the even mix of flint and kaolin isn’t suitable.
Making your own kiln wash is pretty simple, as long as you follow the recipe.
Getting a Permixed Kiln Wash is even easier and more convenient.
When NOT To Use Kiln Wash
Not every kiln requires kiln wash. For some types of kiln shelves, kiln wash can actually be detrimental. Fiber shelves shouldn’t be treated with kiln wash. Fiber shelves are absorbent and would be destroyed by the application of kiln wash.
Some kinds of pottery such as bisque, for example, don’t require the use of a kiln wash. Even for materials that don’t require kiln wash, using a kiln wash is fine when firing bisque pottery, even though it’s not necessary. Unless you have separate shelves for bisque firing.
How To Remove Glaze Without Damaging the Kiln Shelf
When the Kiln wash starts to flack, or you have scratches, or bare spots it’s time to remove and reapply to the bare spots. Kiln shelves are surprisingly fragile in spite of their ability to withstand the high temperatures of ceramic firing. Uneven cooling, thermal shock, or stress fractures can cause shelves to crack or split over time. For this reason, it’s important that the shelves remain structurally sound and undamaged when you remove the kiln wash.
Because the fired kiln wash is harder than the material of the shelf, removing a coat of kiln wash without causing damage can be tricky. Remove glaze without damaging the kiln shelf by using a wire brush to loosen up the kiln wash. While this is more time-intensive than using a scraper, you’re less likely to cause a gauge in your kiln shelf.
Grinding the kiln shelf using a palm sander or similar power tool can save a lot of time. However, power tools lend themselves to errors, increasing the likelihood of damaging the shelf.
Safety Precautions When Removing Kiln Wash
The process of removing kiln wash from shelves requires that the hardened coats be chipped and flaked off using a wire brush or scraping tool.
While doing this, it’s advisable to wear Safety Goggles. This will guard against hardened kiln wash chips getting lodged in your eye. Remember that kiln wash is harder than brick, so take the safety precautions seriously.
Wearing a Dust Mask is also important to protect against the inhalation of dust particles and compounds when removing the kiln wash from the shelves.
Does Kiln Wash Go Bad?
If you found some old kiln wash in a forgotten corner, you may be tempted to use it instead of mixing up a batch or purchasing a new supply.
Because Kiln wash minerals can’t go bad, However, if kiln wash isn’t the expected consistency, it may not provide adequate protection to the kiln shelves.
Is Kiln Wash Toxic?
Kiln wash isn’t toxic, but it can be harmful to your lungs. Potters should get rid of old kiln wash if the level of dust particles contaminates the wash. It’s best to keep your Kiln wash sealed to reduce contamination.
Even so, kiln wash is still a safe material to store and use, provided potters take proper precautions.
While the kiln wash itself isn’t toxic, the combustion of firing a kiln releases chemicals into the air, which are bad for the lungs. Also when the kiln wash is in powder form.
Can Kiln Shelf Paper Be Used Instead of Kiln Wash?
You can use a sheet of kiln shelf paper instead of kiln wash, in some cases, like Overglazes. The two products serve essentially the same function, like using wax paper instead of PAM on a cookie tray.
Because the kiln shelf paper has a lower heat tolerance than kiln wash, it can’t be used with all projects or firing methods. If the kiln is fired too hot, the paper will burn and disintegrate, rendering it useless at best.
When firing projects that require lower temperatures, kiln shelf paper can save potters a lot of time and energy.
Here’s a list of a few types of ceramics that can be fired with kiln shelf paper instead of wash:
- Glass fusing
- Decals
- Overglaze decoration
- Enamels
Kiln shelf paper provided it’s thick enough, can be taken out of the kiln and reused several times. This requires that the paper be at least 1/8th of an inch (0.32 cm) thick. Also, the kiln temperature must NOT rise above 1600°F (871.11°C); otherwise, the kiln paper will catch fire.
Check out Kiln Wash or Kiln Shelf Paper for more information on their uses.
Does Underglaze Stick to Kiln Shelves?
Most underglazes should not become stuck to the shelves. Some underglazes are made with more frit, which can cause stickiness during firing. It can also stick if you apply the underglaze too thick. I have never had my underglaze stick to my kiln shelf.
If you’re not sure if the underglaze will stick to the shelf, it’s safer to err on the side of caution by applying kiln wash anyway; even if it turns out to be unnecessary.
Conclusion
Today we learned that with the proper protection, specifically Kiln Wash, you can make each Kiln Firing experience less stressful knowing that along with some Kiln Cookies you have the best protection when it comes to The Dreaded Glaze Melted to the Kiln Shelf Experience
