interesting question.  I specifically use mundane materials from my enviroment, ie, being a modest mother and an humble housewife, I use junk from my kitchen, like plastic bread tags, wonderbread bags, twisty ties, etc, and junk from my sons, like candy wrappers, broken plastic toys, and junk from the laundry room, like old socks...I am looking for the common, overlooked items that can't be tossed into the recycling bin (yet) and arent good enough for Goodwill and really are junk.

however, I have used the plastic wrist bracelets from hospital stays, the blue plastic case from my old diaphragm, the (never used) plastic bulby thingy that they issued for newborns to be used to suck the snot out --- just in case --- 

recently, a friend gave me an old yellow Yard Birds plastic bag, and I used that.

my work tends to document everyday existance, so, nothing really odd or exotic to report here.

thanks for asking, love, etc Ruby