This weekend one of our party members tried to cast a grease spell on the boot of an enemy. This caused some internal quandry about whether it was allowed and resulted in a GM call.
The spell does give rules for casting on an (employed) object but no specifics on one that could not be simply dropped. This resulted in the ruling that the boot was essentially covered in grease rather than the 10' area so without removing it, it was as if the person were affected by grease wherever they went (whenever they moved). However, aside from not affecting potentially 3 other medium targets or a stationary area that extremely increases the power of the spell in my opinion.
Alternative discussions/thoughts were that it would coat the target (as in greasing clothing, giving +10 to escape artist/grapple but no penalty to moving) or that it couldn't be done at all.
I looked at the FAQs and they seem silent on this subject. Any other sources of information/facts people know that might point to a more definitive answer? (RAW preferred but will leave untagged)
PS: A similar but probably slightly different Q would be what happens if you grease a locked on object such as a locked weapon or strapped on shield. I'm really surprised there's no FAQ on this, but similarly also surprised it's never come up before so maybe just something I'm missing=)