These are some of the molds I've made from polymer clay (I have
hundreds more

).
Actually, the green faces, the skull, and the pink geometric each show both the polymer
mold and the polymer
cast or "pull" later made from that mold... there are also two metallic plastic buttons there to show some geometric items that can be used as dimensional "stamps" for making molds.
Some of the other casts shown were "
highlighted" mostly on their upper portions with gold mica powder (Pearl Ex, etc.) before baking (to bring out details)... I intentionally allowed the powder to get on the background areas of these pieces a bit though since I wanted to cover most all of those pieces (but I kept the powder
off of the background clay in the lower left, pinebranch cast, per normal).
Casts can also be "
antiqued" so that only the bottom portions are colored (with paints, metallic powders, etc.), usually applied, then wiped off the top areas, or sanded off after baking... the skull was antiqued with burnt umber tube acrylic paint, but not that well done).
Casts can also be
completely covered with metallic powders or other colorants too Ithe Celtic weave cast at top was completely covered, but it's hard to see).
Polymer clay molds can be made from virtually any item that's reasonably stiff (and doesn't run away too fast

)
... these particular molds have been made by using plastic buttons, faces on toys & little plastic animals, nature items, carvings of my own, stamps, charms, decorative metal beads, etc. ...(actually the bottom right ones were made with a carved white
eraser which you can also see in the photo, but they could also have been clay molds and turned out the same).
...Molds can also be made from 3D items, or just from
textures --e.g., coarse sandpaper, plastic canvas (blue, above), wavy bottom of plastic box (dark burgundy, above)... those are often used as "backgrounds" or just visual interest too.
Btw, there are
various possibile ways to combine polymer clay and molds:
--polymer clay
molds can be made with non-clay items
--polymer clay molds can be made with baked polymer items
--polymer clay
casts can created from polymer clay molds
--polymer clay casts can be created from molds not made from polymer clay
......these might be
purchased molds (molds for
candies or cookies or soap, silicone molds, wood molds, etc.)
......these might be molds
made by the clayer (from various glues, 2-pt silicone molding materials, crumpled aluminum foil, plaster, etc.)
......these might be "molds"
found around the house (the inside of a paint "well" in a paint mixing tray, a teaspoon, etc., anything with a depression and maybe texture in it)
(Most of those would not be
baked with the clay, though those that are silicone-based could be. ... those also don't include ways that liquid clay can be "cast" in various molds.)
As for ways to
use the casts from polymer molds, there are many!
They can be used just as embellishments and
onlays (on clay items or non-clay ones ...too many to mention!), or for making
beads (even double-sided beads), or as clay
faces for dolls and other figures, etc., etc. Molded items or molded bits are actually used a lot in polymer clay.
Normally I try to
color-code my molds because there are just too many of them to paw through all the time. So most of the faces are made from green clay, animals dark red, geometrics are often another color, nature items too, etc. Some of those above are not color-coded though because they were either made before I started adding color to the SuperSculpey I use, or because they were what I had on hand when the molding opportunity struck! (Some clayers are even known to carry a blob of clay in a plastic bag in their purses, etc., just so they can make a mold from any fascinating shape or texture they see while they're out, then bake it at home.)
I have so many faces that I even numbered those molds on the back... then I also marked the same number on the corresponding cast for each mold after baking it, because sometimes faces can be really hard to recognize when they're molds (innies).
Generally,
releases aren't needed for making polymer clay molds or casts, but it can be helpful in some circumstances, especially when one is new at making and using molds with clay.
The Polyform and Kato clays work fine with a little spritz or coating of plain
water, but the Fimo clays don't like water as much, and for those especially, a little
cornstarch (brushed on with a fluffy brush) will work best (talc powder can be used, but sometimes it's harder to get off the clay after baking-- actually most talc and baby powders have only cornstarch in them these days).
If your clay is particularly soft or sticky, you can also put the clay and mold in the frig or freezer awhile to
cool and firm it up which makes for easier removal.
Molds which aren't flexible at all can make clay harder to get out sometimes too, and for those try cooling, or try pressing the back with a soft wad of clay, or even sticking a pin into the clay kind of sideways to help pull on the cast.
Using a little less clay than will totally fill up the mold makes it easier to get out too, and will leave a nicely rounded edge on the cast... can be interesting to make a cast of just a
part of the mold too by pressing only a little ball or shape of clay into the mold somewhere.
Using
more clay than will fit just inside the mold makes is easy to get out too. Then you can either trim off the excess ....or you can leave the excess to create an interesting background "
frame" around the molded object (can leave it as is, or trim it to any "frame shape" you want).... then when the cast pressed into new clay to make a final piece, the frame will stay as part of it.
Diane B.
GlassAttic....polym
er clay "encyclopedia"
http://glassattic.com/polymer/contents.htm