1. The density bottles constructed are similar to the poly density kit sold by Educational Innovations. See:http://www.teachersource.com/product/poly-density-kit/density. The poly density kit sold by Educational Innovations was originally developed by Lynn Higgins. See:http://www.polymerfun.org/.
2. Method for separating or identifying plastics
3. Perler beads (seehttp://www.eksuccessbrands.com/perlerbeads/) are a good, decorative source of LDPE for this activity.
4. Craft “Pony” Beads (see, for examplehttp://www.walmart.com/ip/19515698) work well as a decorative source of PS for this activity. Plastic cutlery, cups, plates, and bowls are also a good source of PS.