how about using "-" to mean EXCEPT.... as in porcelain -button. Its not exactly a new idea, but your system does not recognise "-"
Why does the "minus" sign not work? For instance, porcelain -button -pendant -bunting -bunting = 37,000 items, INCLUDING BUTTONS, bunting, etc. I'd get a shorter list with JUST "porcelain" meanwhile inundated with silly porcelain buttons.
Another example: "hand thrown porcelain mug" = 44,837 matches.
... and not remotely helpful.
Please enable the minus sign to exclude search terms.

We have started making improvements to search. The more terms you enter into search now, the fewer results it will return:
http://blog.folksy.com/2014/03/28/finding-and-sharing
We are also planning to allow search results to be filtered by category.
Hopefully those two improvements should remove the need for this feature.