The contents of my product have separated in the can. Is that normal?

Gravity can cause some solids to settle on the bottom of the can and slight separation on the top. This is normal.

If working with older paint, use a paint mixing attachment on a drill to reincorporate the solids. If the solids dissolve and the clumps smooth out after mixing from the bottom, the product is in good condition. 

If your water based product has large chunks that cannot be incorporated by stirring, the product has frozen and can no longer be used.