Kiln cookies are a great way to help preserve the health of your kiln shelves. If you are new to pottery, though, you may have wondered exactly what kiln cookies are and how do I make them.
If that sounds like you, rest easy. In this article, we will explore what kiln cookies are, why you should use them, and how to save a few pennies by making your own.
Let’s dive right in.
What Are Kiln Cookies
Kiln cookies, sometimes called kiln paddies or simply paddies, are thin discs made out of high refractory clay that are placed under pieces of pottery during glaze firings. They may also be used by some pottery crafters when they bisque fire large flat pieces.
Why Are Kiln Cookies Used By Pottery Crafters
Their primary purpose is to protect the kiln shelves from dripping glazes that can fuse your wares to the kiln shelf or mare the surface of the kiln shelves themself.
Kiln cookies are also used by many pottery crafters when firing large flat pieces. Sizeable flat pottery like plates and tiles tend to warp and bend due to the tension that can develop across their surface during firing. If the tension is great enough, pieces can even break from the buildup of pressure.
Placing a kiln cookie under such items provides a barrier between them and the hot kiln shelf. This allows the wares to heat more evenly and relieves much of the thermal tension that can develop.
In most cases, if anything breaks, it will be the kiln cookie and not the plate or similar item.
What Are Kiln Cookies Made Of
Kiln cookies are generally made of clay blends with a high refractory factor. One of the most popular blends we see used is 50 percent EPK and 50 percent alumina hydrate.
You can use other clays, but this formulation allows your cookies to be used up to Cone 10 and beyond without issues. This is due to the high alumina content of this mixture.
Many potters recommend adding grog to your mix to help reduce drying time and reduce shrinkage. This is purely a matter of taste, but we do acknowledge that grog can increase the durability of your kiln cookies.
You can also use clays with a high silica content, but these should be avoided if you are going to be doing salt or soda glazes. The high flux content atmosphere these create can cause the silica to melt and fuse to the kiln shelves.
How to Make Kiln Cookies
Making kiln cookies is a very simple project well within the skills of even the newest potter. Here is a simple step-by-step process you can follow.
You will need:
Choose and Wedge Your Clay
The best clays to use for making kiln cookies will have a high refractory factor combined with low shrinkage. Our personal recommendation is to use a high-fire stoneware clay with plenty of grog content.
That being said, you can use any clay you like, and many potters use their bis of scrap clay to save money. The entire point of making cookies is that they will get damaged to protect your kiln shelves.
It is, however, very important that whatever clay you choose to use is well wedged. You need to work the clay to assure consistency and remove any air bubbles that may lurk inside. We like to work 2-4 pounds of clay at a time.
Skipping this step can lead to cracked, blown out, or uneven cookies.
Roll Out Your Clay
Next, you want to roll out your clay to about a quarter inch thickness. We like to use a rolling pin to get smooth results.
There are two tricks that we will pass along to make the process easier. One is to cover your clay with cling film before rolling. This keeps the clay from sticking to the rolling pin and will serve another purpose shortly.
The second is to use two yardsticks as height gauges for your clay. Place them on each side of your clay supported by coins, pottery shards, or whatever you have that give you the correct height, and let your rolling pin ride on them. This assures a constant thickness to your kiln cookies.
Cut Out Your Cookies
Once your clay is rolled out to a uniform thickness, you can take your cookie cutters and cut out your new kiln cookies through the plastic wrap. The pressure of the cling film will give your kiln cookies nice rounded edges.
Let Your Kiln Cookies Dry
Lift your cling film and remove the excess clay from around your freshly formed cookies. Set the cookies aside to dry as you would any other clayware. Take the leftover clay and repeat steps 1-3.
Bisque Fire or Not
The final step for creating a kiln cookie is a point of contention among potters. Most recommend letting your cookies air dry as you normally would and then bisque firing them.
There is another school of thought, though, that suggests your cookies will last longer if you let them rest until bone dry and then use them as is. We have no particular opinion on which method works best.
Pro Tip: If you texture the surface of your cookies, it reduces the surface contact area, provides spaces for glazes to pool away from your wares, and improves airflow during firing.
Frequently Asked Questions
How do you keep a glaze from sticking to a kiln?
There are three standard methods used to prevent glaze from sticking to kiln shelves and other parts of a kiln.
- KIln Wash
- KIln Paper
- Kiln Cookie
All three can be used to catch running glaze before it has an opportunity to fuse to your kiln floor or furniture.
What is the difference between bisque and glaze?
Biscuits (or bisque) describe any pottery that has been through an initial firing but does not have any glaze applied. It has only been matured so that it will be ready for glazing.
Glazes are chemical coatings that are baked into pottery for the purposes of sealing the clays, decorating it, or making it food safe.
These coating literally fuse with the underlying clay becoming part of the structure of the clay.
What is a pottery cookie?
Kiln cookies are small, flat pieces of clay that are put under the pottery during glaze burning. Some bisque potters use it before the firing. Others use bone-dry clay to keep it thin enough to not burn in the glaze.
Do you need to use kiln wash on pottery cookies?
There are differing opinions on whether you should use a kiln wash of cookies. If you are buying cookies, it might be worth the effort to use a kiln wash to protect your investment.
Most potters that make their own pottery cookies consider them disposable items that are created to take damage rather than letting your kiln shelves be ruined. For this group, using kiln wash would be a senseless use of time and money.
As is often the case, it really comes down to preference.
I’m Jessica and I’m obsessed with kilns. I’ve been doing pottery from when I was a little girl and I created TypesOfKilns to help people find the right kiln for their needs.