From stoneware to low-fire, we have you covered for claybodies. As a major NE-regional supplier, we carry clays from all of the major distributors. If you are new to ceramics and not sure what clay might be the one for you, or if you are a ceramics instructor who has to select a clay for your classroom, our experienced staff will be happy to recommend a great product that will fit your projects and your needs. Check out our reference guide including information on recommended clays for tableware, ovenware, sculpture, and woodfiring by clicking here.
We carry clay by all of the major distributors, including Amaco, Miller/Laguna, and Standard. We can easily handle large orders for schools or universities, but we can also sell small quantities of clay, as well! If you are interested in trying out a new claybody, we sell almost all of your clays in 25-lb. bags; we also sell in bulk, too, if you are stocking your university department for the semester or preparing for a busy upcoming show season. Most of our clay comes with bulk discount pricing, too, so the more you buy, the less expensive your per-pound price is! Price breaks occur at 50 lb, 250 lb, 500 lb, and 1000 lb increments.
CharacteristicsCone: 6Wet Color: Red/BrownFiringColor: Oxidation: Speckled Tan - Reduction: N/ATexture: Slightly CoarseConsistency: StandardAvg. Shrinkage 2%: 10.9%Avg. Water Absorption 1%: 1.7%COE x 10-6: 5.64
There are lots of different types of clay for pottery. One of the ways that pottery clay is categorized is the temperature it should be fired at. Low fire is best fired at low temperatures. And high fire clay is best fired in the high-temperature range. But which will suit you best? This article is all about low fire vs high fire clay. I will look at the pros and cons of low and high fire clay, and some other clays in between.
Low fire clay fires between 1940-2109F. Its easy and economical to fire. However, its still porous. High fire clay fires around 2381F. Its strong and waterproof. However, its best fired in a gas kiln, which is less convenient. Mid fire clay fires between 2157-2232F, its strong, waterproof, and easily fired in an electric kiln.
People often talk about low and high fire clay. However, there are actually 3 broad temperature firing ranges. So, the question is not just one of low fire vs high fire clay. Rather, its a question of low, mid, or high fire clay and which one suits you best.
Before going on to look at what these differences in temperature mean, I wanted to say a bit about cones. If you are new to pottery, you may have heard people talking about cones and wondered what they are.
Clay is said to have matured during firing when it has reached its maximum strength and optimal density. I say optimal density because more density does not always mean more strength. At some point during densification, if the clay becomes denser, it also becomes more brittle.
To mature, clay needs a combination of heat and time in the kiln. The combination of heat and time is called heatwork. It refers to the amount of energy that has gone into firing a piece of pottery. Not just the temperature reached.
Cones are small pieces of ceramic that stand in the kiln when its being fired. The cones bend when the pottery has had a particular amount of heatwork. And cones are graded on a scale according to how much heatwork it will take to make them bend.
Whats more, not all kilns have digital control panels. Some kilns, for example, kilns that use kiln sitters and gas kilns need more manual operation. Potters using these kilns still put cones in the kiln to gauge if their ceramics have had sufficient heatwork.
Low fire clay reaches maturity when it is fired, between 1940 -2109F (1060-1154C). On the cone system, this is between cone 04 and 1. These are often referred to as earthenware temperatures because earthenware is the term used for low fire clay.
As stated above, a clay is mature when it has become as strong as it can be. The strength of a fired clay depends in part on how dense it becomes when its fired. If clay is over-fired, that is, fired at too high a temperature, it becomes too dense and will be brittle.
Sintering occurs when the surfaces of the clay particles next to one another bond together. The clay particles also move closer to one another, so the clay becomes denser. Once clay is sintered, it changes from clay to ceramic.
Vitrification occurs when materials in the clay start to form molten glass. This liquid glass fills up the gaps between the clay particles. And when the clay cools the glass solidifies, and the clay is less porous. Low porosity is one factor that contributes to ceramic strength.
However, low fire earthenware clay does undergo the process of sintering. As such, low fire clay becomes sintered ceramic, but it is still porous. This is because it does not undergo the glass-forming phase when it is fired.
Unlike low fire clay, mid fire clay does vitrify when it reaches maturity in the kiln. Mid fire clay goes through the sintering process. Then once it reaches a high enough temperature, the glass-forming materials in the clay, mostly silica, start to melt.
Vitrification is a process. So, a piece of ceramic can be more or less vitrified, depending on whether its had enough heatwork. The more vitrified the clay becomes, the less porous it will be once it has cooled.
Ideally, functional pottery needs to have 2% porosity or less. This means that only 2% of the ceramic body is made up of pores. The rest is made up of solid matter. Many cone 6 stoneware clays can achieve this target of 2% porosity if they are fired to the right temperature.
Like mid fire clay, high fire clay is vitrified and non-porous if it has been fired to the right temperature. When considering low fire vs high fire clay, if you want non-porous ware, then you should choose mid or high fire clay.
A lot of electric kilns fire up to high fire temperatures. However, firing to cone 10 in an electric kiln is very tough on the kiln elements. And you will find you have to replace these more often if you are firing to higher temperatures. When considering low fire vs high fire clay, wear and tear on electric kilns from high temperatures may be a factor.
High fire temperatures are more often associated with gas firing and wood firing. Whilst electric kilns are used for oxidation firing. Gas and wood firing can be used to create a reduction atmosphere in the kiln.
Simply put, an oxidation atmosphere in a kiln contains oxygen. Whereas a reduction atmosphere contains a reduced amount of oxygen. The amount of oxygen present in a kiln will affect what glazes look like.
Choosing the right clay is important, however, its not as simple as low fire vs high fire clay. Selecting a mid fire clay is also an option, and in my opinion, its often the best option. Mid fire clay gives you the best of both worlds. It is strong and waterproof but has the convenience of being easily fired in an electric kiln. Perhaps you dont own a kiln and you are relying on a community center to fire your work. If thats the case, its a good idea to find out what temperature they fire at. And then choose a clay body accordingly.