Orton Pyrometric Cones For Monitoring Ceramic Kiln Firings - Cone 04 (1 Pkg/50) Review (2026)

What Cone 04 tells you

Pyrometric cones do not measure temperature alone, they measure heat-work, the combination of temperature and time that actually vitrifies clay and matures glaze. Orton designed the self-supporting series with a built-in base and an 8 degree lean already molded in, so the cone tips over at the correct point without a plaque or cone holder. Cone 04 sits toward the hotter end of common bisque targets and at the lower end of the low-fire glaze range, which is why potters use it to check hotter bisque loads or confirm a low-fire glaze firing actually reached its mark. Set one where you can see it through the peephole or spy hole, and its bend tells you what your kiln's controller or kiln sitter cannot always confirm on its own, that the load received the heat-work it needed.

Why self-supporting over standard cones

Traditional small cones need a cone plaque or pat of clay to hold them at the right angle, which adds a step and a chance to set the angle wrong. Self-supporting cones like this Orton set stand on any flat kiln shelf on their own, with the lean already built into the cone body. That consistency matters because a cone tilted too far forward or back gives a false reading, bending early or late relative to the actual heat-work delivered. For potters checking multiple shelves in a large kiln, or anyone who wants one less variable in an already finicky firing process, the self-supporting format removes a common source of user error compared to loose cones set by hand.

Pack size and practical use

Fifty cones per package is a useful quantity for a working studio, small school program, or a potter who fires regularly enough to want a witness cone in most or every load. Cones are inexpensive individually, so buying in bulk mainly saves on repeat ordering rather than unit cost. A single firing typically only needs one to three cones, placed at different shelf positions to check for hot or cool spots, so a pack of 50 can last a home studio a long time if stored properly. Occasional firers who bisque or glaze at other cone numbers will use these more slowly, since this pack only covers the Cone 04 heat-work point and not the full range a mixed-firing studio might need.

Storage and handling

Pyrometric cones are sensitive to moisture. A cone that absorbs humidity from the air can soften slightly and bend at a lower heat-work value than it should, which makes the firing look hotter than it actually was. Keep the unused cones in their original packaging in a dry area of the studio, away from a sink, a damp basement corner, or a humid glaze mixing station. This is a normal precaution for any pyrometric cone, not a flaw specific to this product, but it is worth planning for when you decide where to store a fresh box of 50. Handling the cones by the base rather than the tip also helps avoid transferring oils or moisture from your hands before they go into the kiln.

Who this pack fits

This is a good match for potters whose bisque schedule runs hot, or whose low-fire glaze work sits at Cone 04, and who want physical confirmation alongside whatever a digital controller reports. It is a narrower purchase for anyone firing mid-range or high-fire stoneware and porcelain, since those firings need different cone numbers entirely, and for potters who only fire occasionally and would use up a smaller pack before these cones ever risk absorbing moisture. Studios running mixed cone schedules across bisque, low fire, and mid fire will likely want more than one cone number on hand, with this pack covering just the Cone 04 point in that lineup.

Frequently asked questions