slime or mold?
My ww start has been in the fridge for about 2 weeks and I pulled it out last night to see if it was still alive enough to revive. What I found was that (as usual) a darkish sludge had settled to the top. What I also found (not so usual) was that there were spots or pockets of very dark sludge here and there across the top. There were no fuzzies or other signs of typical mold. When I put a spoon in, the underside looked very normal (although the smell was very pungently sweet, not a pleasant smell). As I stirred, it looked like the dark spots had been where there had been pockets in the start where the sludge had pooled and condensed as moisture left the start. I took out a tablespoon and gave it a full feeding, and this morning it has risen nicely and smells very pleasantly fruity. Do you think I'm safe to bake with this? The sludge on top looked rather slimy, but not moldy, but I don't want to poison us either. :)
Assuming your fridge is working and the temperature is somewhere between 32-40 degrees, you should not have to worry about any toxins. Sounds like 'hooch' to me - the alcoholic by-product of the yeasties feedings on the dough. If you haven't fed your starter in awhile, this by-product will rise to the surface and lead to the type of odor you described.
Again, if it's been refrigerated I wouldn't worry about it. As a general rule, however, unless you're away on a trip, you probably don't want to go two weeks between feedings - you're basically starving your yeast, and too much alcohol build-up will eventually ruin your starter. Also, if you're going to store your starter in the fridge between uses, you might want to consider going with a starter that is more firm - it'll take longer to produce the alcoholic liquid floating on the top, and that will help rid your dark sludge problem.
Larry
Thanks for the advice Larry! I am pretty new to this, and sometimes things get put on the back burner longer than I'd like, so I can use all the help I can get.