Editing Polymer clay (section)

==Composition==
[[File:Figurines from Clay Critters.jpg|thumb|left|Figurines made from polymer clay.]]
Polymer clays contain a basis of PVC resin and a liquid [[plasticizer]],<ref name="Duketox">{{ cite web |url=http://duketox.mc.duke.edu/polymerclayresults2.pdf |vauthors=Stopford W, Turner J, Cappellini D |title=Determination of the Magnitude of Clay to Skin and Skin to Mouth Transfer of Phthalates Associated with the Use of Polymer Clays |publisher=Division of Occupational & Environmental Medicine |date=2003-08-03 |url-status=live |archive-url=https://web.archive.org/web/20120222115555/http://duketox.mc.duke.edu/polymerclayresults2.pdf |archive-date=2012-02-22 }}</ref> making it a [[plastisol]]. Polymer clay plastisol is also categorized as a [[plastigel]] because of its [[rheology|rheological]] properties.<ref name="Plastisols">{{cite book |author=Sarvetnick HA. |title=Plastisols and organosols.|location=New York|publisher=Van Nostrand Reinhold|year=1972}}</ref> It is a high yield [[thixotropy|thixotropic]] material: when a sufficient force is applied, the material yields, flowing like a viscous liquid until that force is removed, whereupon it returns to being a solid. This plasticity is what makes it useful as modeling clay as opposed to putty or paste. Plastigels retain their shape even when heat is applied, which is why polymer clay does not melt or droop when oven cured.<ref name="Plastisols"/> Various gelling agents are added to give it this property, such as aminated [[bentonite]], metallic soaps, or fumed silica.<ref name="Patent">{{cite news |vauthors=Severs ET, Lebanon M, Frechtling AC | title=Composition comprising a gelling agent and a dispersion of a vinyl resin in a plasticizer.| publisher=United States Patent Office, patent 2,753,314.| date=1956-07-03}}</ref>
 
The base resin can be modified in various ways. Mineral oil, [[lecithin]], and odorless mineral spirits can be added to reduce its viscosity or alter its working properties. Small amounts of [[zinc oxide]], [[kaolin]], or other fillers are sometimes added to increase [[Opacity (optics)|opacity]], [[elastic modulus]], or [[compression strength]].  Polymer clay is available in many colors, which can be mixed to create a wide range of colors or gradient blends. Special-effect colors and composites include translucent, fluorescent, phosphorescent, and faux "pearls", "metallics", and "stone."