Have you read of people using cornstarch or baking soda with polymer clay and you wondered what that was all about? Why would you use it? And which one should you use? Is cornstarch better? Or is baking soda?
Supporting Polymer Clay During Baking
If you make a round bead with polymer clay, and put it in a tray to bake it, what keeps that bead from rolling around in the pan? And if you bake more than one polymer clay bead, what’s to keep them from all rolling to the same corner where they’ll all bake together where they touch? You need to put your raw clay bead on some surface that will keep them from rolling around. Some people use accordion folded paper. Others use polyester fiberfill or quilt batting. But another simple option is to place them all on a bed of cornstarch or baking soda.
If you’re making a flat pendant, for example, when you set it on a pan or tile it will have shiny spots on the back. You can use a piece of paper under your clay to prevent this. Or, you can just set the pendant on a bed of cornstarch or baking soda.
Irregular shapes that need a little support can be partly buried so that the powder will support them and they won’t droop during baking.
Protecting Polymer Clay from Browning
Most ovens heat with an electric element that gets very hot and glows orange while the oven is heating up, or when the element cycles on to keep up the oven’s temperature. Unless you’re using a convection oven that circulates the heat, this direct radiant heat can cause your polymer clay items to toast brown even if your oven is set to the correct temperature! This is particularly a problem for light colored and translucent polymer clays.
To help prevent this color change, it’s really important to cover your clay during baking. One method is to completely bury your raw clay creations in baking soda or cornstarch while they bake. This will allow them to heat to the full temperature that’s required for a proper cure, and still protect them against the direct heat of your oven’s element. Do make sure, though, that you add a some extra baking time because it does take a bit more time for the heat to travel to the clay when it’s buried like that. I’ve written a whole series of articles on Baking Polymer Clay that will help answer many of your baking questions.
Which One is Better?
Cornstarch or Baking Soda with polymer clay, which one is better? To an extent, it’s just a matter of preference. Both will work well for the situations above. But there are a couple of things to keep in mind.
Removing the Powder
See, sometimes the powder you use will stick to your baked clay and you have to remove it. The simplest way is to just wash them in running water. Most of the time, it will come right off. But know that cornstarch doesn’t dissolve in water and can sometimes remain slightly embedded in the clay. You might need to give it a quick scrub with an old toothbrush. Baking soda, however, is water-soluble and will dissolve completely. This means you won’t have any residue.
Can you use rice flour, wheat flour, or other white powders to support polymer clay during baking? Well, you could. They would work just like cornstarch or baking soda with polymer clay. But the difference is they get gummy when you try to wash them off. Cornstarch doesn’t get gummy in water. Other starches such as arrowroot, tapioca starch, or potato starch might work for this purpose, you’d just have to try it. But since cornstarch is so readily available, it’s what is commonly recommended. If you’re not in the US, cornstarch might be an unfamiliar term. It’s just the US term for corn flour. It’s what we use to thicken a sauce and it what’s used to starch laundry.
By the way, baking soda is also called Sodium Bicarbonate. It’s not the same thing as baking powder, which is baking soda with other acidic powders added. Baking powder will work, but it’s just so much more expensive that it’s better to stick with baking soda.
I’ve also been asked about using talcum or baby powder with polymer clay. Can you use it in the same way? Well, most baby powder today is cornstarch and not talcum powder as talc isn’t so good for babies to breathe. So check your label. If it’s cornstarch, sure, give it a try. But if it’s talcum powder you may find that it is too hard to remove from the baked polymer clay.
Using Cornstarch to Smooth Polymer Clay
While baking soda is kind of grainy, cornstarch is silky smooth. This quality of cornstarch makes it excellent for smoothing the surfaces of your raw clay before baking. When we form our clay pendants and sculptures, for instance, we often leave fingerprints. You can remove them by dipping your finger into some cornstarch and smoothing it over your unbaked polymer clay.
Don’t do a “scrubbing” action, though, or you could bury the particles of cornstarch into the clay and you won’t be able to remove them. There’s a fine line between “enough” smoothing to get a nice surface and “too much” smoothing that will give you a white coating. Try it, experience will show you the way.
Cornstarch and Baking Soda can Cause Leaching
Polymer clay is made with oily plasticizers that allow it to stay flexible and strong after baking. Those plasticizers, however, will leach out into absorbent materials. This is why it’s never a good idea to leave your unbaked polymer clay on a piece of paper or on a bed of cornstarch or baking soda for long. The plasticizers will leach out and leave your finished piece more brittle than it should be. After baking it’s not a problem, though, as the plasticizers are locked between the molecules of the plastic.