Polymer and metal clay Hallmark Stamp by Nancy LT Hamilton
Detail of polymer “wood grain”.
Polymer clay is a very elastic and flexible compound that is hardened by firing at low temperatures. It is used in the arts and crafts field. It is composed of Polyvinyl chloride (PVC) and liquid plasticizers called phthalate esters. There is new information that these phthalate esters pose a health threat. See Wikipedia’s information about phthalates. Supposedly, Polymer clays are being reformulated with less toxic(?) plasticizers. Heating polymer clays beyond recommended firing temperatures releases toxic gases (350 degrees +).
There are quite a few Polymer Clays out there today. I will only discuss the ones that I have experience with. I am not a polymer clay expert. I’ve just worked with it for so many years that I feel like it’s an old friend. I bought my first polymer clay book around 1992, Nan Roche’s The New Clay: Techniques and Approaches to Jewelry Making and that was my introduction to working with the material. I eventually fell in love with Polymer Clay’s sculpting abilities. It has been very exciting to watch the medium develop from a child’s toy to a respected artist’s medium.
Lark Books has recently released (March, 2011) a new book written by Ray Hemachandra and Rachel Carren, that illustrates the growth of sophistication and talent in this medium. The book spotlights some of the best polymer clay artists working with the medium today (and for a few artists represented, in the past): Masters: Polymer Clay: Major Works by Leading Artists ($12.34 at some famous online bookseller who I won’t mention because of their new, stupid policy of not allowing California residents to participate in their affiliate program – it’s a political thing). It is a fabulous book! I mean, wow, awe inspiring work. Nice job, Lark!
The Clays (that I’ve worked with, remember)
Sculpey by Polyform. Sculpey is the first clay that I ever worked with and still work with today. I use regular Super Sculpey as a base for larger pieces, as a mold, as a form for creating shapes with metal clay and many other uses including handles for files and other tools. It’s also great to carve. Sometimes you get these little white orbs in it when you bake it. It’s not an issue when it’s under other clay. You can read about the history of Sculpey at the Polymer Clay Web. NOTE: When mixing clays – be sure that the firing times are the same!
The second clay I worked with was Fimo. I had read that it was a stronger clay but, it was difficult to handle as it was very crumbly and difficult to work into a “plastic” form. There is now a Fimo soft available that is much easier to work with. Although, I feel the new clay suffers a lack of strength and elasticity. The history of Fimo is rather interesting and you can find that information at the Staedtler Fimo site.
Fimo Classic 
Fimo soft
Now, I work mostly with Premo, also made by Polyform. It’s not too brittle and is somewhat flexible after firing. It comes in a lot of colors and is easy to work with. None of these clays are really flexible (post firing) – especially if the pieces are very small and thin. In the piece below, that I made, I tried Fimo, Original Sculpey, Fimo soft and eventually settled on Premo for making the grass and the small pebbles. All the other clays proved way too brittle and I had to redo the grass several times until I settled on the Premo.
“A Slice of Heaven“: Metal Clay, Sterling, Polymer Clay, Colores Enamel. 
“A Slice of Heaven” open and back.
Using the clay
Polymer clay , like paints, is color mixable. Using just the primary colors, black and white, you can make thousands of colors. It’s best to record the amounts used in each color so that if you want to make it again, you can. Of course, I never do that. I just remix by eye. I’m a very lazy woman and hate record keeping (ex-accountant here).
But, assuming you aren’t lazy and an ex-accountant and that you want some control, it’s good to know how to do this correctly. So, I will elaborate.
The lazy woman’s (or man’s) way: To make different colors, just take pinches of the colors you want to mix, squish them together with your hands, run them through the pasta machine and violá – a new color.
Some people use the above template to determine sizes for color mixing. Personally, I think that the Clay Measuring Template is just silly. Then again, I don’t do a lot of caning and I can only assume that it would be a helpful tool for that. But, why not just use the C-thru Circle Template from Amazon that’s $6.24 and has a bunch more circles than the clay template? I would image it would be much more versatile! The whole idea is consistency so, any template should work. I (stupidly) bought one and now, it sits in my template basket waiting for some love.
There are also Clay Rulers. Two that come to mind are: Donna Kato’s, Marxit and Amaco’s, PolyRuler. They both work on the concept of leaving marks in your rolled out clay to show you where to cut your clay. When and if I measure, I use a standard ruler and cut with this cool little tool available at Micro-Mark, the Parallel Cutter ($26.75). You can set the width of the blades and it cuts nice, clean parallel lines. I also use it to cut metal clays. 
My favorite lazy woman’s (or man’s) method, when forced to measure, is to use circle cutters or square cutters or any old cutter. Simply roll out the colors to the same height – either using even stacks of cards and a rolling pin or use the same setting on your pasta machine. Take out your little circle cutters and cut out circles of colors. Of course, you would want to write down how many circles of red, white and blue equal that fabulous purple you made (ahem). You can cut a little hole in the top of your finished color and write the formula on the back. Hook all those colors together with a ribbon or other attachment and you’ve got a recipe book that could (?) double for a necklace.
I like these cutters by Ateco because there are a variety of sizes. You can also find them at Polymer Clay Express, which is a great source for tools and materials.
More later kids, off to work! 8/31/11