Here's a technique you can use to make fire with polymer clay.

More photos are coming...

1. Make a skinner roll with fire colors.

Choose fiery colors! Of course...

Transparent colors work well.

You can make a "rainbow" skinner roll with multiple colors, but if you plan to reduce them to a small size it is better to use a smaller number of colors.

2. Make two swirled rolls too. One with fire colors, one with smoke and ash colors.

Don't blend the colors -- just combine rolls of different colors into a ball. Then roll it out into a roll and twist it up and make it a ball again. Repeat one more time until there is interesting detail on the surface. Finally roll the roll out.

Make a second roll with slightly different colors, maybe transparent or dayglow colors mixed in, or blend some unique colors and roll those into a swirled roll.

3. If the clay is very sticky let it cool off, or even put it in the fridge for a little while.

In the next step you'll slice the rolls into thin discs. If the log sticks to your blade, it will quickly deform the rolls as you cut them. The resulting discs are easier to work with if they remain more circular. You can also reform the discs after every few cuts if you're in a hurry.

4. Slice each one of the rolls into varying sized, discs.

Cut slices between 1/32" and 1/8" thick, and not necessarily exactly vertically through the roll. Vary the thickness randomly. Don't be too careful. Fire is mostly random anyway.

5. Pile up the slices in a more or less random order, from among all the slices of all the rolls.

Before I discovered how useful a pasta maker was, I still wanted to make some layered effects. So I would create small piles like this with two, three or four colors, repeated over and over again.

To make fire you want to select random but contrasting slices, one after another.

Now stick them together like a pile of coins (horizontally on the table, of course). Place them offset with respect to each other, rather than all in a neat line. I'll often overlap two of the same style of disc, but rarely two of the smoke colored disks.

6. Compress the sides to form a rough roll, but don't actually roll it.

It actually is a good thing that the edges of the disks get crushed over in unpredictable ways. Add to that by pushing some one way and some the other. Twist them, crush them a bit and ultimate squash the whole pile down to more or less of a roll, but don't actually roll it out much. It doesn't need to be round.