how do you remove silicone from plastic?

Answer 1

Read the whole article cited to start. I am assuming you mean silicone caulk or sealant, but you didn't say.

"Silicone caulks are the hardest caulk to remove. There are not really any solvents you can buy to easily remove silicone caulk. Multiple applications of strong alkaline compounds like sodium or potassium hydroxide can soften silicone caulk. However, these chemical compounds are dangerous and can often burn you or the materials surrounding the caulk. You can try oven cleaners or strong powdered cleansers that you mix with water to a paste consistency. Apply these carefully to the caulk with a cotton swab. These compounds can dull plastic laminate tops, acrylic and fiberglass tub and shower units and many other bath and kitchen materials. You must work slowly and carefully." (1)

This company sells silicone caulk removers, but it's more than I'm willing to do to read and find out if they can be used on plastics.
http://www.amtexchemical.com/pages/13/

Here's one about uncured silicone sealant:
http://www.gesealants.com/sealants/residential/library/usingsealants/uncured.shtml

And cured:
"On hard plastics or painted surfaces, including cars: Use rubbing alcohol and a soft cloth. Do not use mineral spirits. " (2)

If you need more specific information, ask a more specific question.

Answer 2

Remove Silicon Caulk