Most of the polymer clay articles I’ll be posting here will not be brand-specific, so for simplicity I thought I’d put my curing recommendations for common polymer clay brands into a single post which I’ll reference as required.

Unless otherwise indicated, the recommendations are my own based on extensive testing. They do not always agree with the manufacturer’s instructions on the packaging!

You might need to adjust temperature or time for your own oven’s characteristics, for instance if the temperature fluctuates significantly or the oven is prone to spikes of high temperature. An oven thermometer is a good investment as the actual temperature inside an oven is sometimes quite different from what’s set on the controls.

There are also situations where normal curing recommendations are deliberately significantly exceeded to achieve a particular effect. These are outside the scope of this article.

Regular Polymer Clays

Polymer Clay Brand(s)	Recommended Curing Temperature and Time
Kato	Normally, 150°C (300°F) for 40 minutes (the 10 minutes you’ll see on the packaging is just wrong and will never give satisfactory results) For even greater strength, 155-160°C (315-325°F) for 40 minutes (some colours will change more than when curing at the slightly lower temperature) For a flexible cured piece instead of a rigid one, 150°C (300°F) for 20-25 minutes
Premo	130-135°C (265-275°F) for at least 40 minutes, and preferably for 1 hour
Pardo	To optimise clarity (e.g. with Pardo Translucent), 150°C (300°F) for 30-40 minutes According to the manufacturer, 120°C (250°F) for 30 minutes
Fimo	According to the manufacturer, 110°C (230°F) for 30 minutes I don’t use Fimo much, but usually cure it the same way I cure Premo, with great results
Sculpey III	According to the manufacturer, 135°C (275°F) for 15 minutes per 6mm (¼”) of thickness, but I’d suggest curing for at least 40 minutes even for small pieces Note that I do not recommend using Sculpey III as it is not strong enough
Mixed brands without any Kato, or with only a small proportion of Kato	130-135°C (265-275°F) for 40 minutes to 1 hour
Mixed brands with a significant proportion of Kato	150°C (300°F) for 40 minutes

Curing Mixtures of Polymer Clay Brands

You can safely mix different brands of polymer clay in your work, in both uncured and cured states. For example, you might make various parts of a piece from different clays and then put them together before curing, or you might mix clay from several different brands to get a new colour or clay consistency to work with.

When mixing clay brands, I recommend curing at the highest standard curing temperature out of all the brands, for maximum strength. To minimise the chance of discolouration, I also recommend covering the clay during baking. My preferred method is to bury the clay piece in a bed of bicarbonate of soda (baking soda), which is safe for all clay brands I’ve tested. If doing this, increase the curing time as the bicarbonate of soda acts as a partial insulator and it will take longer for the clay buried in it to heat up.

Note: The “traditional” advice for mixing clay brands is to cure at the lowest temperature for any of the brands, for the longest time of all the brands. I do not recommend this unless your work will be fully supported, for example a decorative element that sits inside a metal bezel. Curing at the lowest temperature will leave the mixed clay piece in a weak state.

Liquid Polymer Clays

These curing details are what I suggest when the liquid polymer clay is directly visible, e.g. when used as a protective or shiny coating or a clear medium to suspend other items in. When liquid polymer clay is used as a softener or for strengthening bonds between pieces of clay, just cure the piece as you would normally, using the temperature and time for the brand(s) of solid clay.

Polymer Clay Brand(s)	Recommended Curing Temperature and Time
Kato Clear Medium	150°C (300°F) for 10-15 minutes if it will be finished with a heat gun to achieve full clarity, otherwise 30 minutes
Translucent Liquid Sculpey	According to the manufacturer, 135-150°C (275-300°F) for 30 minutes; higher temperatures increase transparency
Sculpey Bake & Bond	According to the manufacturer, 135°C (275°F) for 30 minutes
Fimo Deko Gel	According to the manufacturer, 110°C (230°F) for 30 minutes