How to Sand Fiberglass

by Contributor

This article will provide information on how to sand fiberglass. This is extremely important when conducting fiberglass repairs or prepping fiberglass for painting.

When sanding fiberglass, you will save much time by using an orbital sander. Theses are relatively inexpensive at hardware stores. Also be sure to use a soft head-pad on the sander as this will make it easier. Start with the highest grit sandpaper, 100 girt works well, to remove any high spots or delaminated fiberglass. You can use sandpaper that is either peal and stick, or you can spray adhesive to the back of regular paper.

Start sanding slowly and with little pressure until you get the hang of it. Once all the high spots are taken down, check for any voids or holes need to be filled. Use a fiberglass putty sold at home repair stores, and follow the directions.

After the fiberglass putty cures, use your sander again so that any holes that were filled are now sanded flush.

Now change sand paper to a higher grit, I prefer 1000 grit. This will help smooth up the fiberglass laminate. Again, start by using as little pressure as needed, you do not want to take away too much fiberglass material.

Finally, clean all the dust off the laminate with a rag and some acetone. You are now ready for to paint the fiberglass or repair the part.


  • check Check classifieds for a used sander
  • check Be sure to cut the sandpaper to the size of your sander head
  • check Be sure to clean the fiberglass of dust before using putty or painting
  • check Always use safety equipment and have proper supervision.


  • close Be careful not to apply too much pressure or you can sand right through your fiberglass laminate.
  • close Have proper ventilation when using acetone

Items you will need

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