(OOC: Not going to try the old 'wet it, heat it up, then cool it down' approach to a clean break of the glass? I was almost expecting that. Okey dokey.)
*The old brittle glass shatters with a fairly-loud but somewhat muffled crack, pieces falling inwards and hitting the ground with a crash. Kel hears the sounds of guards or someone nearby shouting 'Hey, what's going on over there?'. With the light source, he's a dead giveaway, and there's not much time til those voices get close enough to see what's going on!*