Hi,
I have been working on dip coating of acid catalyzed TEOS sols with an incorporated pH indicator dye (phenol red sodium salt) after dipcoating, I am drying at 125 degrees C for 1hr and have nice films that change color in acid or base solutions. However I seem to have a problem with basic solutions (sodium bicarbonate) at a pH of around 9 dissolving the coating from a glass microscope slide and other glass substrates. Any suggestions?

-Jake