Here at Hot Clay we are proud to offer all our customers unlimited technical support on products bought from us. Most of the questions we get asked are answered on this page. If you can't find what you are looking for then simply contact us, we really are here to help. 

For kiln schedules, beginner guides, a glossary of clay terms and more, see our Knowledge Base.

CLAY TYPES AND USING CLAY

I am a complete beginner. Where do I start?
Take a look at the Getting Started page, visit our Knowledge Base, or just contact us, we are here to help!  Top

Which clay should I use?
Take a look at our Which Clay page for information on choosing the right clay. Top

What is the best way to store my clay?
Store your clay in a cool dark place, well wrapped and sealed in plastic. The plastic bag the clay comes in works well. Top

What is the difference between Earthenware & Stoneware?
Earthenware is fired at lower temperatures usually around 1000-1080°C. At this temperature the clay remains porous and the glaze will be a separate layer adhering to the surface. It is often used for decorative pieces or traditional storage vessels.
Stoneware is generally fired to higher temperatures. Stoneware glaze firings are usually around 1200C-1300C. At these temperatures the clay fuses and becomes strong and impervious to water. The glaze fuses with the clay. Stoneware biscuit firings are usually around 1000°c and glaze firings 1200°C to 1300°C. Because of its strength and water-resistance it is frequently used for making tableware and also sculptural work. Top

GLAZES AND GLAZING

Can Earthenware glazes be used on Stoneware clay?
Generally not. You should choose a glaze that is suitable for your clay body. Some stoneware clays are dual purpose and can be used at earthenware temperatures. Top

Can I mix Glazes together?
Yes, some glazes can be mixed to produce new colours. Always test first - experiment! Top

Do powdered glazes give the same quality finish as prepared glazes?
Yes, if they have been mixed correctly. Top

Why is my earthenware glaze crazing?
The glaze may not be suitable for the particular clay. Clays and glazes expand and contract at different rates so it is important to choose a glaze that is suitable for your clay. All our glazes state which clay bodies they are suitable for. Crazing can also be caused by glazing over an underfired bisque, so it is worth checking the temperature of your bisque firing. Some glazes are designed to craze - check the label! Top

Do you have a remedy for Pinholing?
When small dots of unglazed or depressed areas appear in the glaze surface, this is called "pinholing". Pinholing occurs when gases in the glaze and clay bubble up to the surface. The gas bubbles pop and a 'hole' appears, which doesn't fuse over.
Remedies:
• Wipe clean bisque ware before firing
• Spray bisque ware lightly with water prior to glazing
• Try a slower bisque firing cycle to give the carbon more time to burn out
• Fire the glaze at a slightly higher temperature
• Hold the top temperature of the glaze firing for a soak of 15 minutes. This will keep the glaze in a liquid state a little longer. Top

My glaze has settled. Does it matter?
Glaze settling may result in firing problems so it is always recommended that you thoroughly mix your glaze before use. When a glaze settles, some of the components of the glaze collect in the bottom of the container so your glaze will be missing potentially key elements if you fail to mix them in before using.
Settling can be caused by adding too much water, or by the growth of bacteria in the glaze, which can lead to loss of suspension. To prevent bacterial growth, do not introduce possibly contaminated objects such as brushes into the storage container or return used glaze to the storage container.
Glazes should be stored in a cool dark place to prolong its life. Top

Are your glazes food safe?
All our Vitraglaze glazes are lead-free and non-toxic. Where toxic materials are present in Vitraglaze glazes this is in a safe form where they are chemically bonded to render them "not bio-available" and therefore safe to use and safe after firing. Please be aware that the term ‘food safe’ can only really be applied to the final fired piece, and since our glazes might be used in a variety of different ways we cannot categorically say (and nor can any other supplier) that our glazes will render your pieces food-safe. Final pieces with a textured, crazed or matt surface can harbour bacteria and so may not be considered food safe. If fired correctly Vitraglaze glazes should be food safe, but the only way to make certain would to have it tested by Lucideon, the official testing body in the UK. Top

KILNS AND FIRING

What temperature should I fire my kiln?
For information on firing your work, see our Firing Up page. Top

How fast should I fire my kiln?
For information on firing your work, see our Firing Up page. Top

Can I open my Kiln when it is still hot after the firing schedule is complete?
It is best to let the kiln cool as much as possible if you can. If the door is opened when the kiln interior is still over 200°C then the pottery may crack or be weakened due to thermal shock. Top

Some of the bricks in my kiln have cracked, should I worry?

With some kiln constructions cracking may sometimes occur because of stresses caused by the heating and cooling of the kiln. Opening the kiln too early will increase the risk of bricks cracking. However, as long as they are not structural even severe cracking will not affect the firing performance of your kiln. Top

My kiln smells when I begin a firing, is this OK?
Organic matter present in clay and the binders in glaze begin burning out at quite low temperatures and can produce strong smelling fumes. This will die away as the kiln reaches 600°C. With most firings the level of toxicity in fumes is very low, but it is best not to work in the same room as your kiln and good ventilation of the room in which your kiln is situated is important. Top