I have been using K-36 primer for some time now.
I've noticed we can now get lightweight bondo, glazing putty, etc. are there any lightweight primer-surfacers?
Could I mix micro-balloons or talc with K-36 to lighten it up?
Thanks,
Jim

Jim, I've mixed microballoons and primer, but only as a filler, not as a sprayable primer. K38 and K36, done it with both.

K36 is pretty light, however, K38 is just a bit easier to sand because of the higher solids content. The both wet sand beautifully.

Jim, DuPont makes a very light weight water based primer # 210 S....works great and does not add much in weight since most of the material is water and evaporates as the primer dries. I have used this primer on weight conscious pattern planes with great results. Easy clean-up is an added bonus Richard