How do I polish Crystal Clear™ or other urethane plastics?

We are often asked how to attain (or restore) a smooth, gloss finish to the surface of a casting made from a Crystal Clear™ urethane plastic, and offer the following buffing technique using progressively finer grit sand papers and sanding gels to improve surface finish.

Every casting surface is different. For surfaces that have severe imperfections, you may need to sand with coarse grit sandpaper prior to moving onto the finer grit grades. If this is the case, we suggest starting with 120 grit followed by 220 grit and then proceed to using finer grit grades.

Sanding the Surface

  1. Begin by sanding the abraded surface that you wish to restore with fine grit sandpaper (320 grit) until any prominent protrusions or grooves are removed.
  2. Next, sand with finer grit sandpaper (400 grit).
  3. Follow with ultra-fine grit sandpaper (600 grit). Note: Water may be used with ultra-fine grit sandpaper ("wet sanding") to reduce particle clogging on the sandpaper and minimize heat buildup.
  4. Next, wet sand with super ultra-fine grit sandpaper (800 grit). After this step, there should be no visible scratches and the surface should appear smooth and translucent.

Polishing the Surface

We recommend the Novus™ brand Plastic Polish system to achieve a final glossy finish.

  1. Optional: If there are still some scratches or fine imperfections present, you can polish with Novus™ #3 Heavy Scratch Remover and rinse under water. Dry off casting to inspect surface.
  2. Finish with a final polish using Novus™ #2 Fine Scratch Remover, and rinse under water. Dry off casting to inspect surface. Repeat this step until surface is perfectly clear.

Important: Results may vary due to a number of variables such as configuration of the casting, quality of the original casting, etc. As a result, Smooth-On can not guarantee or warrant that the above procedure will work for everyone. A small test on a non-critical area of the casting or different casting will be an indicator of whether or not this procedure will work for you.

This FAQ article is offered as a guideline and offers possible solutions to problems encountered during mold making and casting. No warranty is implied and it is up to the end user to determine suitability for any specific application. Always refer to the provided Technical Bulletins (TB) & Safety Data Sheets (SDS) before using any material. A small scale test is suggested to determine suitability of any recommendation before trying on a larger scale for any application.