[RobNk]

Hi,

I'm not much of a chemist, but I've been doing some work in a university lab (environmental engineering).  The lab bench, especially around the sink, keeps getting this orange/brown gunk on it.   (I'll try to get camera and post photos later.)  It seems to come out of nowhere.  No one knows what it is (including others in the lab who know more chemistry than me), and this lab doesn't work with that many chemicals.  We've noticed that if we use RBS detergent solution on the black bench surface, the color appears.  And since there are detergent bottles around and in use, this is probably part of the cause.  This detergent solution has NaOH in it, and when I dripped some NaOH solution on the bench surface, that also caused the orange/brown color to appear.  It's hard to see on the black bench top, but when I wipe with a white tissue, the tissue becomes orange/brown.   We did this for a while and seemed to clean the bench top.  But then it started reappearing after a few days.  Do you have any  thoughts on what this could be?  Could the bench top be degrading?  It's supposedly 15-20 years old.  The lab room was used before by others so we don't know what's been in here.   The most common chemicals in this lab are probably the ethanol and detergent used to clean things.  Other chemicals are used only in minute quantities.

Rob

[CopperSmurf]

I read your post and made me think a bit. You mentioned it's around the sink, so it's most likely bacteria. There are orange-colored bacteria around and it's gross.

I also had orangey stuff and orange stains coming off from the lab bench as well before but had no idea how. Not 100% sure, but could it be rust from old equipment on top of it? Or a possible stain from a previous chemical that never came off before? I used to have a lot of stuff...

[fledarmus]

What is your sink made of? Is it mounted on top of the bench, or underneath? Is it possible that the stains are rust from either the underside of the sink rim or from the sink fixtures?