Sometimes static electricity will cause clumping. If it happens wipe your powder measure down with a dry drier sheet borrowed from your wife, Or buy your own box and throw in a couple sheets in the brass tumbler when it's running. Really cuts down on the fine dust.
Had the same experience with Retumbo once, but it performed fine. The smell of bad powder is unique, smell a new can and you will be able to tell the difference between some that has gone bad.
OK thanks , are we talking about moisture clumping ( to break it apart ) or all of the above ?
I'm not having any problems, I wanting to know for future reference. !