I started a Rumtopf off a few months ago every thing seems to be going ok but I,ve noticed that on the outside of the pot I seem to get like a brown syrupy substance,which looks a little bit like camp coffee which a few of you may remember. I keep wiping it away but it always re-appears a few weeks later. I,ve tasted the Rumptopf and it tastes fine, in fact it taste blumming lovely. Has anyone else experienced this?