As Jiktiling says micromax drier really fast! i used exactly the same gun metal a few weeks back and i was suprised at the speed it dries!...this was on normal porcelain 450x450 tiles
....yep, I agree. My 1st thought was that Micromax goes off pretty quick, plus just 1 coat of 'sealer' on a suspect load of t'internet slate probably didn't help...