"10. What is BLUSH, and how do I remove it?
Blush may form over the fast mix MAS Hardener and MAS Resin. The MAS Slow mix generally will not blush. Blush is noticeable as a slippery film formed over the cured surfaces. It can be removed with warm water and a sponge (rinse and wipe)."
I read that as their system uses amines in the hardener and both hardners will blush. I further read the MSDS (COMMON NAME - Cycloaliphatic Amine) as containing amines. From our resident epoxy technician, epoxymoron, I understand that blush is caused by amines and any amine presence in the product will potentially cause blush. If it was me, I'd just assume that there was blush present and take the 10 seconds to rinse and wipe before I started sanding.
Just a Columbia 28