How to Remove Mold Release Residue on Plastic Parts

Injection molded plastics must be cleaned before they are safe to use.
Injection molded plastics must be cleaned before they are safe to use. (Image: louche silicone image by Unclesam from Fotolia.com)

You can quickly remove mold release residue from plastic parts without causing them any damage. Mold release spray is often applied to plastic injection molds to prevent sticking and control the uniformity of the product. These sprays leave an oily residue on the plastic pieces they form. This thin layer of mold release residue can be cleaned from a plastic surface with a few common household products. Once the oils have been completely removed the part is ready for paint or assembly.

Things You'll Need

  • Rubber gloves
  • Mineral spirits
  • Wash cloths
  • Powdered laundry detergent
  • Running water

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Put on rubber gloves and fold a wash cloth in half twice before pouring mineral spirits in the center of the cloth until a circle the size of a drink coaster is wet with solvent.

Sprinkle about a tablespoon of powdered laundry detergent onto the mineral spirit spot and squeeze the cloth closed to mix the two together.

Open the cloth and rub all the surfaces of the plastic parts with the mineral spirit and detergent mixture.

Fold the cloth to a new section and reapply the mineral spirit and detergent mix until you have cleaned away all the mold release residue. Feel the surface of the plastic to see if it still feels oily and slick.

Rinse the plastic parts under running water once all the release residue is gone to wash off any soap powder and mineral spirits that remain. Dry the plastic parts completely with a new wash cloth.

Tips & Warnings

  • Silicone mold release agents that are made specifically for thermoplastic injection forming are often designed to be easily removed with soap and mild solvents.

References

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