Cracked Polymer Clay

There are many surface crackle techniques for polymer clay. Most involve applying a special paint. The one discussed here involves crackling the clay itself.

Why? Hasn't crackling been SO done already by so many? I wouldn't disagree. But due to a recent discussion where someone on Facebook asked the gang how to do one specific effect, I took the bait. Not having done much in the way of crackling as a surface technique, I proposed theories (reverse engineering) on how it was done.

Naturally, one must test their theories... right? So the fun begins.

Which specific effect am I talking about? Something Agnes did. Agnes posted her work on flickr: She mentions something about "controlled crackling".

One curious soul posted Agnes' crackled beads photo on Facebook and asked the subscribers how it was done. The query started a nice long thread. No one knew for sure. But there were lots of suggestions about how to do general crackling effects.My mind lit up! Gears were smokin'. Agnes' controled crackling effect had so much potential.

My own analysis of her pieces - the greatest clay stiffness was where the fractures were largest - in the center. As distance from the "center line" increases, the stiffness decreases and the fractures are smaller. Conclusion - the application of a temperature gradient, where the temp is highest in the center, then decreased on either side. Then the clay was stretched. But because the surface was partially cured, it fractures instead doing a smooth stretch. Later the surface was backfilled with a dark pigment (paint or ink).

One main reason I love polymer clay. It's so versatile.

My exploration began - how to replicate that pattern without knowing how Agnes did it. "Ouch", the rusty gears are a'spinnin'.

Basic supply list

  • polymer clay
  • black acrylic paint or ink
  • tissue blade or NuBlade
  • pasta machine (I use a Mercato Atlas)
  • hand roller
  • wet/dry sandpaper (200, 300, 400, 600 grits)
  • controlled crackling tools
    • medium size tin can (1)
    • heat gun (2)
    • perforated ladel (3)
    • tablespoon (4)
    • this list is endless...
  • tin can - I cut the bottom off of a 5"- 6" tall tin can and flattened that end; leaving the top of the can alone. I made a setup where the tin can was held in place

  • Techniques (click on images to see larger versions)

    "Narrow nozzle" technique

    • approx. 1/4 block white clay
    • #4 thickness setting for crackle layer
    • tin can (flattened on one end)
    • heat gun
    • silver pearl back sheet
    • black acrylic paint, ink

    1. Roll out small white sheet of clay (#4 thickness), approx 2"x3".
    2. Aim a narrow stream of hot air onto the clay. Duration depends on the temperature. it isn't necessary to brown or burn the clay. it's not even necessary for the surface to feel hard. the surface just needs to be partially cured. I've tried various temperatures (350, 550, 750, 950) for various lengths of time (2, 3, 4 minutes), but haven't found the magically consistent recipe yet with this technique.
    3. Run the sheet through the PM at #4.
    4. Back the crackle sheet with a raw clay sheet of similar size. For this piece, it's backed with silver clay.
    5. Roll piece through PM at #2, rotate 90 degrees, roll through PM at #3. at each step, stop to observe the crackling effect.
    6. Once you have achieved the desired crackling effect - shape, trim, embellish, bake.
    7. To highlight the crackling:
      1. Lightly wet sand with 300 or 400 grit sandpaper.
      2. Smear black paint/ink, all over the surface. use a small paint brush to poke the paint into the nooks and crannies.
      3. Wipe off excess paint/ink with dry paper towels.
      4. Heat surface to set paint/ink
    8. Sand surface to remove any paint or ink from the surface and to smooth it out. Start at 200/300 grit, progress to 400/600. Sand sides and back.
    9. Finish, embellish as you like.
    status: unfinished


    "Mega crackles" technique

    • white clay
    • #4 thickness setting for crackle layer
    • tin can (flattened on one end
    • heat gun
    • silver pearl back sheet
    • black acrylic paint

    The only major difference between this piece and #1 is the length of time heat was applied.

    status: unfinished


    Tablespoon technique

    I placed a large tablespoon on the clay and aimed the heat gun at the spoon. The curvature of the spoon meant as the spoon's bowl curls up away from the clay, there's less heat, so the fractures are smaller.

    Now wondering what a fork effect would look like...

    status: unfinished


    Perforated ladel technique

    I used a perforated label instead of a tablespoon. If you look carefully, there are at least four little circle areas that correspond to the holes in the ladel.

    status: finished as a technique sample


    Shedded crackles

    I think this was done using the narrow nozzle technique. The difference with the approach on this piece:

    • I was brutal with the applied heat. After running the piece through the pasta machine, so much of the cured clay fractured pieces simply fell off. I was about to toss the sheet with the pieces. However, the remaining surface looked so interesting. It reminded me of tree bark or something.
    status: finished as a technique sample


    Standard heat gun

    At least I think that's what it was. :)

    Here I decided to get a little out there with paint; more than just to highlight the fractures. The first one is more phenonmenal than what comes across in the photo. It really looks and feels like a whole new substance. Paint colors: Golden's carbon black, quinacindrone gold. Paint dabbed into the piece, then lightly sanded in randon spots.

    The second one: carbon black and Eberhardt's Gold Powder. The gold reflective bits aren't showing up in the photo. My cell phone's camera isn't up to the task.

    status: unfinished


    Rated R!

    Here's a naked crackle piece; done using an electric charcoal starter. The clay sheet has been contured to help highlight the fractures.

    status: finished as a technique sample


    Soldering Iron

    I think this is my favorite piece so far. And yes, I used a soldering iron to do the crackles. I held it in one spot for a while then moved forward a bit. Then randomly paint dabbed (black and quina gold) and sanded just along the fractures.

    You could say it is an example of controlled fracturing and sanding. I'm so excited with the effect, my teeth hurt! :)

    status: unfinished


    Secret technique

    I'm not going to state what tool I used here just yet. Those of you who know me well enough could probably deduce it, based on the using the soldering iron in the previous piece. Frankly, I was surprised I thought of it and surprised by the result. But I'm going to be practicing this for a while. It's so rad but requires a very special touch.

    status: finished as a technique sample


    more techniques may appear! :)



    Enjoy clayin' and crackin''.


    Last update to this page: 12 May 2014. Send comments, questions or suggestions to Desiree McCrorey.