How to Thin Polyester Resin
- 1). Pour the polyester resin that you wish to thin into a small bucket, filling the bucket no more than 3/4 full to allow room for the addition of the thinning agent and mixing. Carefully measure the amount of resin you place in the bucket while pouring using a measuring cup and take note of the total amount.
- 2). Fill a measuring cup with acetone measuring 10 percent of the amount of poured resin by volume.
- 3). Add the acetone to the bucket of resin a small amount at a time. Stir the resin with a wooden stir stick as you pour the acetone, mixing the resin constantly until it reaches the thinness desired. Stop mixing the acetone and resin when there are no longer signs of separation between the two substances in the bucket. Use the thinned resin immediately before it sets within the bucket.