The Google is a wonderful thing. Oh, you guys are pretty good too. Found this on the Sika web site. Thanks all, we're probably done here.
"Its also a good point to note that in dry conditions a light mist of fresh water from an atomiser spray bottle over the surface of the Sikaflex will enhance the skinning and initial cure speed due to the increase in available moisture. This is most helpful in dusty conditions to avoid dirt particles being lodged in the uncured surface before the Sikaflex skins."
Dry? Dust? Yup!