Is It Normal for Gel Coat to Be Sticky, and How Can It Be Solved?

It is common for polyester gel coat, when used as the first layer, to retain a slight stickiness. This helps achieve better cross-linking with subsequent resin layers. However, if the gel coat remains sticky when used externally (such as on the surface of a product), it can pose a problem, especially when repairing molds or applying surface refinishing coatings.

To address stickiness, you can add a wax solution to the unsaturated polyester or vinyl ester gel coat (typically at a ratio of 2-5%). This wax solution, made from paraffin and styrene, will form a very thin barrier between the gel coat and the air during curing, allowing the wax to polymerize at the surface, resulting in a hard, non-tacky finish.

However, for large-scale gel coat renovations, it is advisable to use air-dry gel coats rather than adding wax solutions. Adding wax can lead to potential bonding issues and reduce surface gloss.