PolyShrink Techniques Gallery/ Shrinking- Oven

Shrinking in an Oven

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Oven baking is a good choice if you have lots of small pieces to bake. It can also be easier for baking very large pieces that can difficult to keep evenly heated with a heat tool.

Pre-heat your oven or toaster oven to 300º to 350º F (148º to 175º C). Preheating is really important, because of the temperature "spike" as the oven heats up. The initial temperature can go much higher than the setting.

Baking Surface- We recommend non-corrugated cardboard (also called chipboard) for baking. Chipboard is the same type of cardboard as on the back of a legal pad. It can be purchased at art supply stores.

Unlike a metal or teflon surface, cardboard pulls less heat away from the PolyShrink as it's being heated. As a piece of PolyShrink warms up, the first part to start shrinking is the outer edge, leading to curling toward the center. Some curling during shrinking is normal, but lessening the heat "pull" of the baking surface helps prevent problems.

When baking in an oven, you have the option of pre-heating the cardboard once the oven is up to temperature. The cardboard will not act as a heat sink since the PolyShrink is going onto a warmed surface.

Hand Manipulation- Although it won't be necessary often, flipping the piece over part way through shrinking can be helpful in exposing the center of the piece to heat.

Size and Shape- It's a good idea to monitor the baking of extra large, long, skinny or complicated shapes. Some manipulation may be needed.

You can also try lowering your oven temperature so that shrinking happens more slowly, and hopefully more controllably.

Is it necessary to use a separate oven from one that food is prepared in?

The Material Safety Data Sheet (MSDS) for PolyShrink describes it as non toxic, even when heated to hundreds of degrees beyond normal baking temperature. Heating PolyShrink itself is safe. But since you can't verify the safety of the enormous number of art materials that might be used with PolyShrink, you may wish to use a separate oven for baking.

Follow any directions that come with your art supplies concerning adequate ventilation. When baking, some artists opt for the ultimate in ventilation by placing their toaster oven on an outside porch or patio.

Is It Done Yet?- Shrinking generally takes several minutes. If the time goes over 5 minutes, the oven temp is too low.

Pieces will not necessarily lay flat. They should look uniform, without bulges around the edges.

If the piece isn't perfectly flat, cool it in a flattened position using cardboard, or an acrylic or wood block. This should be done immediately after removing from the oven, while the plastic is still warm and flexible. No need to press hard- a small amount of pressure is all that's needed.

Troubleshooting-

Despite your best efforts to avoid PolyShrink curling to the point of sticking to itself, it can happen. As soon as you notice that it's stuck, stop heating and allow the piece to cool a for 5-10 seconds. Pull gently and you'll hear a tiny “snap” as the joint comes apart. You can now return the piece to the oven to Using this method, it is almost always possible to save any piece that has stuck together.

You may find it helpful to take a look at the heat tool shrinking page for step by step photos of the shrinking process.