I have always been taught that the reason RainX interferes with good repairs is because it interferes with the bonding between the resins and the glass.

Lets look at a bullseye….

If the bullseye is filled and cured, the repair resin would be retained mechanically by the outer layer of glass. If pit filler were used and it bonded molecularly with the repair resin that bond should keep it in place. This would be especially true if the bullseye were “drilled” which would expose a clean glass surface along the inside of the drilled area which would not be contaminated with RainX and allowed for an additional mechanical bond. It would seem to me that now one would have a several types of bond on the pit which should retain it. I have seen “lost” pits, however, where the loss was attributed to “RainX”.

Could it be that RainX is not interfering with the resin/glass bond but really altering the adhesion properties of both resins to the point that neither mechanical nor molecular bonding are very good anymore? Why does Pit filler seem to be more susceptible to RainX than repair resin?

Should the repair resin be cured first and then the pit filler added and cured? I have never seen it done that way, but, maybe it would prevent the resins from mixing and encourage a mechanical bond between the two. Maybe repair resin and pit filler won’t bond to each other and have to cure in a transitional zone between the two “liquid” resins.

Anyway….. Although I have never argued with the RainX explanation I have always questions it’s validity. If anyone know the “scientific” answer I would be interested to know it TOO!




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