Orton SSB Self-Supporting Pyrometric Cones, Loose, for Kiln Firing

Orton SSB Self-Supporting Pyrometric Cones – Firing Control for Your Kiln

Orton SSB cones are self-supporting pyrometric cones. You place them in the kiln and, after the firing, you can see whether the heatwork you wanted has been reached. The cone bends as it fires, and the degree of bending shows you how far the firing has progressed. You do not need a cone plaque, because the height (1¾ inches above the base) and the 8° bending angle are already built in, according to Orton. The cones can be placed on any flat surface.

A cone measures heatwork, which is the combined effect of temperature and time, and not a single temperature value. The faster the kiln heats up, the higher the bending temperature. That is why the options offer three temperatures for heating rates of 15, 60 and 150 °C per hour. They refer to the last 100 °C of the firing climb and apply to an oxidising atmosphere. In reduction, the conversion of the bending angle into a temperature changes.

Using the cones

Place the cone on a flat surface, such as the kiln shelf, so that you can see it through the spy hole and it does not touch any ware. For checking, you will often use several cones side by side: a lower-numbered guide cone as a warning, the target cone and a higher-numbered guard cone as a safeguard. This shows you whether your firing was too short, right or went too far.

Which cone number to choose

Choose the number according to the firing range of your glaze or clay. The temperatures given help you find the number that matches your firing curve: if your kiln heats up slowly, the bending temperature is close to the first value; with fast heating, it is close to the last.

Do not heat up too quickly

If the kiln is heated too quickly, the cone surface fuses, according to Orton, and the binders form gases that cause the cone to bloat. Cones that are fired quickly should be pre-fired (calcined). The cone will then indicate the firing more reliably.

Orton SSB pyrometric cones product details

• Manufacturer: Orton
• Type: SSB, self-supporting pyrometric cone
• Height: 1¾ inches above the base
• Bending angle: 8° built in
• Temperature data: for each cone number at 15, 60 and 150 °C/h
• Atmosphere: Orton chart values apply to an oxidising atmosphere
• Cone number: Choose the cone number from the options.

You will also need: a kiln with a spy hole, if you want to watch the cone during firing.