What is a Kiln?
According to Wikipedia – a kiln is a thermally insulated chamber, a type of oven, that produces temperatures sufficient to complete some process, such as hardening, drying, or chemical changes. Kilns have been in use for hundreds of years to turn objects made from clay into pottery, tiles, and bricks. Kilns are a vital part of the production of all ceramics. Pottery pieces require high temperatures so chemical and physical reactions will occur to permanently alter the unfired body. In the case of pottery, clay materials are shaped, dried and then fired in a kiln. The final characteristics are determined by the composition and preparation of the clay body and the temperature at which it is fired. As a beginner in pottery, there is no better feeling than owning your ceramic kiln. But some major considerations should not be overlooked when purchasing your kiln. You will need guidance so you won’t get the wrong kiln. A lot of potters have purchased a glass kiln instead of a ceramic kiln. Although they can be used interchangeably, I will still advise you to get the right kiln.
Before we talk on the differences between a Glass Kiln and a pottery kiln, I want us to examine the types of Kiln available.
Types of Kilns
- Electric Kilns:
Electric kilns are the most common type of kiln used in pottery and glassmaking. They are quite cheap, and they are easy to use; you can even plug the small ones to a regular wall socket, making them accessible to small pottery operations. Electric kilns always fire in oxidation meaning there is enough ventilation in a completely controlled environment, which yields consistent results with glazes.
- Gas Kiln
Gas kilns use natural gas and fire in a reduction process, which doesn’t allow oxygen in the kiln during firing. Reduction firing results can be volatile but typically yields rich earthy colors. It’s tough to maintain stability, so gas kilns are most ideal for one-of-a-kind masterpieces.
- Wood Kilns
This type of kilns is fueled by wood. It has been in use for thousands of years too. They are very labor-intensive because they need continuous stoking and re-fueling of the fire to keep the kiln at reliably high temperatures. A wood kiln firing can take three times longer as it would be in an electric or gas kiln, and it needs to be examined the whole time.
Glass kiln is a special kiln. Glass kilns rarely fire over 1700F because glass is a low-fire material. Glass kilns assure that heat radiates not only from the sides but from the top of the kiln as well. This helps counter glass’s sensitivity to various temperature variation, and it is better for the nature of most glass pieces. Glass Kilns have elements on their lid that aid even firing. The element on the lid is important for Glass fusing. Glass fusing is when various pieces of glass are combined into a single cluster by heating them to a point where they become soft, and the material flows across each piece.
Glass Kilns are mostly electric. They usually come in oval or rectangular designs. The rectangular designs cool faster than the oval glass kilns. The bigger the glass kiln, the more energy you will need to run it, so try to match the voltage and amperage requirements of your desired kiln to what you have available in the space you’ll be housing it. If you decide on a kiln that has more energy requirements, you should be prepared to make further funds in its installation
Size of Glass Kilns
There are various sizes of glass kilns and vary based on the number of projects you want to do. Glass Kilns generally come in 3 sizes. There is 9” x 11”, 18” x 18”, 23” x 27”.
The 9” x 11” glass kilns are the smallest size of glass kilns. They are best for firing beads, jewelry, small pieces, and test items.
The 18” x 18” glass kilns are perfect for those whose intent is in creating slightly bigger fused glass pieces, or more jewelry than can be fired in a single round in a small kiln.
A 23” x 27” glass kiln is a common size for average glass artists creating medium-sized fused pieces and deeper slumping projects. Anything bigger than this size is specially made for large commercial production
Unlike the pottery kilns, an average glass kiln will sell for $750, while the large commercial kilns sell for $4500+. Summarily Glass kilns are more expensive when compared to pottery Kilns. Glass kilns are investments and they should be done with adequate precautions. You can order for a glass kiln on amazon by clicking here.
These are also known as Ceramic Kilns. They are the most popular kilns used today by artists. Most pottery kilns are powered by electricity and they range in size from small units that can sit on your tabletop to units the size of your fridge.
Ceramic kilns are classified by their temperature rating. A lot of commercial ceramic glazes and clay are fired between 1828 F and 2345 F.
Ceramic kilns will only have elements in the sidewalls of the kiln. They usually don’t have elements on the top of the kiln. There are two reasons for this. When elements in the kiln get over 1800 F they begin to get soft like cooked spaghetti and therefore need to be supported by hollows cut into the brick of the walls of the kiln. Another crucial reason ceramic kilns are generally side firing is that artists generally fire multiple levels of pottery in their kiln. The elements in the kiln can radiate between the shelves when mounted in the side.
Most ceramic Kilns fall into four different sizes: 11.25” x 13.5”, 13” x 15”, 18” x 20”, 23.5” x 22.25”.
The 11.25” X 13.5” and 13” x 15” kilns are regarded as a tabletop or countertop kilns. They are small and they can heat up to 2000 F. Most tabletop/countertop kilns are electric thereby making firing easy. They require 120 volts, 15-17 amps. These kilns can be used with a standard home outlet, thereby making it a perfect and easy fit for any garage or new home studio. Although the 13” x 15” kiln is a bit bigger, it should be used for small pieces like mugs, pans, and plates.
The 18” x 20”, 23.5” x 22.25” kilns are often called the Evenheat ceramic kilns. These kilns fall into the category of the most popular size available. In these kilns, you will be able to easily fire larger amounts of bigger pieces like pots, plates, and bowls. These kilns are intended for mid- to high-fire stoneware. It can fire up to 2350 F. Large kilns like these have wide diameters and easy to load depth, and they usually come equipped with controllers of your choice.
As mentioned earlier, you will need to determine whether the materials and glazes you would like to use require a high, medium-high, or medium-low temperature ceramic kiln. Low-fire materials include earthenware, stoneware can be intended for either mid-firing or high-firing kilns, and porcelain requires the highest temperature levels.
As I have said earlier, kilns are investments and they should be done with adequate precautions. I have selected the kiln I feel will be appropriate for a pottery beginner. You can order it on amazon by clicking here.
DIFFERENCE BETWEEN GLASS KILN AND POTTERY KILN
|GLASS KILN||POTTERY KILN|
|Glass kilns generally heat a single layer from the top||Pottery kilns heat multiple layers from the side|
|Glass Kilns fire around 1700 to 1800 F||width=”312″>Pottery Kilns fire around 1900 to 2450 F|
|Glass Kilns have elements on their lids.||Pottery Kilns do not have elements on their lids|
The major difference between a glass kiln and a pottery kiln is that glass kilns generally heat a single layer from the top and pottery kilns heat multiple layers from the side.
The reason why glass kilns are designed to heat from the top is that the majority of glass projects tend to be relatively flat. With the heat being radiated from the top, the entire face of the glass “gets” the heat at the same time. This keeps temperature differences within a glass project even and it prevents cracking.
The same uniform heating results can easily be attained by simply slowing down the firing in the kiln. Firing at low temperatures tend to make the pottery and glass even.
CAN YOU FIRE GLASS IN YOUR CERAMIC KILN?
Kiln-fired glass, or warm glass as it is also called, is typically done in an electric kiln at temperatures lower than ceramic temperatures. 1300-1500 degrees F is typical. Due to the lower temperatures involved, most ceramic kilns are capable of firing glass. However, electronic regulators are particularly useful for glass firings, as the temperatures have to be controlled exactly during certain stages of firing.
As earlier indicated, glass kilns have elements on their lid but if doing small pieces of glass, a lid element is not essential for fusing. If you are making jewelry, for example, the tabletop ceramic kilns without lid elements work fine. But the larger your glassware gets, the more complex it gets to do without a lid element.
Most Ceramic and Glass Kilns sold today come with Automatic controllers. Both types of controllers almost always have a programming mode called Ramp and Hold Mode which is perfect for writing glass programs. If your ceramic kiln has a Kiln Sitter instead of an automatic controller fusing glass will be very difficult and is not recommended.
CAN YOU FIRE CERAMIC IN A GLASS KILN?
Just because you can fire glass in your ceramic kiln does not mean you can fire your pottery in a glass kiln. A typical glass kiln does not go beyond 1750 F. A typical mid-fire stoneware clay needs about 1900 F to 2200 F to bake, thereby firing your pottery pieces in a glass kiln might be difficult.
HOW TO FIRE YOUR GLASS IN A POTTERY KILN?
- Cut your Glass:
You are going to have to cut your glass into whatever shapes you want to fuse. You can cut your glass into circles, squares, triangles, or whatever shapes you want to use in your design. Kindly note that you can also stack your glass pieces and fuse them directly on the kiln shelf, or you can lay them over a slumping mold to create a three-dimensional piece.
- Place your glassware in the kiln and turn it on:
Arrange and stack your glassware however you want it to look once they are fused. The largest piece of glass will have to be at the bottom and then you should stack the smaller pieces on top. The temperature you use to fuse your glass in the kiln depends on the look you’re going for. You should consult your kiln manual for specific instructions on how to set a firing schedule.
- Fuse your glass:
Fire your kiln to between 1350-1370 degrees Fahrenheit for your glass to fuse properly. This temperature is if your glass is not in layers. Program your kiln to reach around 1460-1470 degrees Fahrenheit to achieve a full fuse if your glass is stacked in layers. If your kiln is not a programmable one, my advice will be for you to fire your ware slowly. If you are not sure about how dry a piece is you can fire slowly to make sure all the moisture in the piece evaporates properly. You should consult your manual for the slowest programmable speed.
After you are done with the fusing process do not open the kiln until it’s cooled off below 100 degrees Fahrenheit Opening the kiln prematurely can cause your glass to break, and you might burn yourself.
Whether you are looking for a big investment or the first step on a journey to what could become a life-long passion, you will need to have an idea of the kind of kiln that will suit you. In this article, I have talked about the types of kilns, the principal use and differences between Glass Kilns and Pottery Kilns.