Sweating Crock?

Hi everyone!
I am new to this forum, but it looks fantastic!  I am eager to explore around and start sharing and experimenting with you all.
The reason I joined this forum today - was to seek advice.
I have been using a 2 gallon crock to make Kombucha in for the last 9 months or so, and the exterior is becoming increasingly oilier.  There is always tea in the crock, and it seems to me that the crock is slightly porous - pushing out trapped oils in the stonewear.  But that seems wrong.  I am starting to worry that perhaps the previous owner had kept auto grease or something like that in it!  The finished kombucha tastes great, and there seem to be no other problems other than the oily residue on the exterior.  I am starting to have second thoughts about sharing it though, as i do not want to be feeding motor oil to my friends unknowingly!
Has anyone else encountered this? 
Any help would be much appreciated!
Thanks!!!
Drew Nelson

DrexNexlo wrote:
  I am starting to worry that perhaps the previous owner had kept auto grease or something like that in it!  The finished kombucha tastes great, and there seem to be no other problems other than the oily residue on the exterior.  I am starting to have second thoughts about sharing it though, as i do not want to be feeding motor oil to my friends unknowingly!

What does it smell like (the oil), It is not uncommon to try to seal clayware with wax (bee or paraffin) or fat (Lard or Tallow) or maybe even veg oil. Motor oil would smell that way I think.