I have found that with the many years I've been sharing my polymer clay work online I often get a lot of questions about different the techniques and processes I use, which is great because crafters are trying to learn new things and further improve their skills. Some of these questions are quite advanced and some we can consider quite basic if we've been working with polymer clay for a while, as this "basic" knowledge tends to become a second nature. One of the questions I get a lot and frequently see asked online is "Can I mix brands of polymer clay?" This includes both mixing colours from different brands and also having a variety of brands together on one piece. I don't usually think anything of it and often leave this kind of basic information out of my tutorials and posts unintentionally, purely because I am so used to these processes.
I think a lot of particularly new polymer clay crafters have this concern and become quite nervous about the topic of mixing brands due to the baking times and temperatures recommended on their clay packaging. I have been working with Sculpey III since day one of crafting, later picked up some blocks of Premo for my collection and have just recently had my first taste of Sculpey Soufflé. The only thing is, the baking time and temperatures vary, so how can you mix them?
If we break it down, Sculpey III has a baking temperature of 275°F (130°C) with a recommended baking time of 15 minutes per 1/4 inch (6mm) of thickness. Premo and Sculpey Soufflé on the other hand both have the same baking temperature of 275°F (130°C), but differ from Sculpey III in that it is recommended to bake for 30 minutes per 1/4 inch (6mm) of thickness.
For a general rule of all brands, don't bake lower or higher than the temperature on the packaging. If you bake lower, the clay in the centre of your piece won't have enough temperature going into it in order to fully cure. The piece may seem baked on the outer layer, but the inside could be under baked, meaning the clay will be brittle and most likely break at some point. At the other extreme, if you bake over the temperature on the packaging you risk burning your clay. The baking time on the other hand is different. Similarly to the lower temperature, if a piece is not baked long enough then the heat won't have enough time or strength to reach the clay in the centre, resulting in brittleness and breakage. But if you actually bake the clay to the recommended time or even longer, it ensures the clay is fully cured which will give it strength. Baking it longer is generally fine as it allows enough time to ensure everything bonds together. So getting back to the varied baking times between Sculpey III, Premo and Sculpey Soufflé, if a piece has a mixture of these I will bake it at 275°F (130°C) and at a time of 30 minutes or longer. This is due to the Premo and Sculpey Soufflé needing to be baked for at least the 30-minute mark. While the Sculpey III doesn’t need as long, it won’t hurt it to be left in longer because it will actually help strengthen it.
The photos in this post are all photos of kawaii polymer clay charms I have made using a mixture of the brands mentioned. Some parts of the charms are custom colours I have mixed using the different brands, while others have sections made with varying brands. They were all baked in my oven at 275°F (130°C) for 30-60 minutes.
So overall, my top tips to take from this would be:
1) Yes, you can mix different brands of polymer clay.
2) Use an oven thermometer to monitor the temperature- don't let it exceed the recommended temperature.
3) Polymer clay bakes from the outside to the centre. Ensure you are baking your clay long enough that the heat has a chance to reach the middle. Pulling the clay out of the oven too early can result in it being under baked and therefore brittle.
4) It is best to bake for the longer recommended time out of the brands you are mixing. This will ensure all clays have enough time to fully bake through, while also helping to strengthen them.