Polymer Clay Baking Chart 2026: Time and Temperature by Brand

Five major polymer clay lines, five different bake numbers. The chart below puts them side by side, with the package-directions disclaimer up front: lines occasionally re-formulate, and the wrapper in your hand is always the final word.

Bake numbers vary by chemistry, not by quality. Sculpey, FIMO, Kato, and Cernit each tune a different PVC and plasticizer blend, and each formulation cures fully at the temperature where its chemistry gels and fuses. Mixing brands inside one piece complicates the math. The chart below covers each major line on its own, then walks through the practical questions that come up around oven verification, mixed brands, and underbake versus overbake symptoms.

The Brand Chart at a Glance

Each line is rated for a specific temperature and a thickness-based time. The standard reference is minutes per quarter inch (6 mm) at the thickest point of the piece. Numbers below reflect manufacturer guidance current as of May 2026.

Important disclaimer: bake numbers change between manufacturer revisions. Always read the package of the exact line you bought before each project. The table above reflects manufacturer guidance current as of May 2026, but lines occasionally re-formulate, and the wrapper is the final word.

Why Brand Temperatures Differ

Polymer clay is PVC particles suspended in a plasticizer system. Each manufacturer picks a slightly different polymer and plasticizer blend to hit a target stiffness, color clarity, and feel after cure. The published bake temperature is the point where the PVC particles gel and fuse with their plasticizer system into a stable solid.

FIMO and Cernit settle in at 230 F because their chemistries gel and fuse at that point. Sculpey lines tune toward 275 F. Kato pushes higher to 300 F because the formulation is built for a firmer, stronger cured body and needs the extra heat to fully cure. None of these is better or worse than the others. Each is tuned for a different working profile, and each cures fully at the published number.

Time per Thickness, Not Time per Project

The chart above is per quarter inch (6 mm) at the thickest point of the piece, not per project. A flat 3 mm earring needs roughly 15 minutes at the package temperature. A 12 mm-thick figurine body needs roughly 60 minutes (two quarter-inches), even though the wrapper might only print 30 minutes. Underbaking thicker pieces is the single most common reason figurines come out brittle and crack at the joins.

The fix is to measure thickness at the heaviest section of the piece and scale the bake time accordingly, holding the temperature constant at the package number. Longer at the right temperature is safe. Hotter than the package is not.

Verify the Actual Tray Temperature

Even with the right number on the dial, your oven may not match. Home ovens commonly run 25 F or more off their dial reading at tray height, and the difference between 275 F and 300 F is the difference between a clean cure and a scorched edge.

Place an oven thermometer at tray height, on the surface where the clay actually sits, not on the rack mid-air and not next to the heating element. Preheat fully, let the oven cycle once, and read the thermometer. Compare to the dial setting. If the reading is 20 F off, adjust the dial accordingly and recheck weekly. Toaster ovens swing harder than full-size ovens and benefit from a foil tent or covered ceramic dish to shield the clay from the element. The oven thermometer guide walks through what to look for in a unit and how to read it.

What If I Mix Brands in One Piece?

Mixing brands inside a single piece is common in cane work, color matching, and rescue blends. There is no universal mixed-brand bake number, and the chart above does not solve the problem on its own.

The standard starting point is to bake at the lower of the two temperatures for the longer of the two times. A Premo and FIMO Professional blend, for example, would start at 230 F for at least 30 minutes per quarter inch. The risk is that the higher-temperature line stays under-cured at the lower setting and the cooled piece is brittle.

Always test the exact combination on a scrap chip from the same blend before committing to a full piece. Bake the chip, cool it fully, and press a fingernail into the surface. If it dents easily, extend the time. If the chip still chips after a longer bake, the two chemistries are not compatible at a shared temperature, and the piece needs to be built in one line. Kato at 300 F mixed with Sculpey III at 275 F is the most common failure case here.

Underbake and Overbake Symptoms

Knowing what each failure looks like is faster than guessing.

• Underbake: the cooled piece feels finished but snaps under stress. Earrings break at the post, figurines crack at thin connectors, and a fingernail pressed into the surface leaves a dent or chips a flake. The fix is rebaking at the package temperature for the full time. A second bake on baked and cooled clay is generally safe. The cracking guide covers under-bake patterns in detail.
• Overbake: the surface scorches, edges brown or blacken, and the room may smell strongly or smoke. Vent the room, lower the dial, and verify the actual tray temperature with a thermometer before the next bake. A foil tent or covered ceramic dish protects the surface in toaster ovens where the heating element sits close to the clay.

For oven calibration specifically, the oven thermometer guide covers what to verify and how often. The support during bake guide covers the support choices that prevent overhang cracks during cure. The cracking guide is the companion troubleshooting read for after-bake failures, and the beginner toolkit covers the rest of the kit. For a figurine where bake settings make or break the result, see the build notes on the signal mushroom figure.