grow box help

HI, i've just started making my first grow box, out of a filing cabinet about three feet high, with the base about 1.5 sq. feet. i removed the cabinets from the filing cabinet, and am planning on putting two 150w CFL's inside for a SOG grow. im going to put a air vent at the top with a fan for exhaust hooked up to a carbon filter, and an intake hole at the bottom side. i have just run into a problem, what should i use for a door? this may sound really noobish, but i need something that will be light tight and keep the scent out. any help is very much appreciated and other tips as well, I'm relatively new to growing.
also, i have been using water and molasses to water my baby right now while it has been flowering, is this going to actually effect the bud in a very noticeable way?
Thanks guyz and galz