Hello Steve,

Correct me if I am wrong, but my guess is that this is an area on the kayak where, after fiberglassing, you introduced stress (perhaps by clamping and then gluing etc.). If so, then the glass fibers in this area are now under tension/compression. When you sand into this area (into the fibers under tension and/or the epoxy that is holding the stressed fibers in place)the fibers start breaking and/or the epoxy/glass bond starts creeping. When this happens you get an immediate pimpling of the glass - with white spots as a result.

To see this effect firsthand, glass a small panel about 12 inches long and let the epoxy cure fully. Introduce stress into the panel by bending it - use tape spanning from end-to-end to hold the bend in place. Now start sanding the panel - stressed fibers will begin to break and move, causing the telltale white pimples to appear.

This pimpling of the glass can also occur simply by leaving the kayak in the hot sun - the epoxy softens slightly and any area of the kayak that has had enough stress introduced, especially if introduced after glassing, wants to relax and can start to form the dreaded "white pimples".

The only cure for this is to sand the glass off of the area in question and reglass.

Hope this helps.

Joe Greenley
Redfish Kayaks