Advice - cleaning outdoor ceramic glass patio table.

CB64

Need advice on cleaning an outdoor ceramic glass patio table. Its a dull ceramic - not shiny. Bought second hand in the box, can't remember seeing any stains when unboxing. Just uncovered table after winter and there is what appears to look like a water mark/stain on the table.  It won't come out with just hot soapy water (using washing up liquid) and I know you can't use anything abrasive on ceramic table tops.  Any idea what I can use that won't damage the table. 

Farway

How about toothpaste?

May sound daft, but it is used to remove "fogging" of car headlights

Of course test on underneath hidden part first

ArbitraryRandom

I'd also go the other way and say vinegar cleans lots of things. 

If that doesn't do it, I've used t-cut (scratch remover for cars) on a ceramic hob before and it worked a treat.