How to Cure Polymer

Polymer clay needs to be 'cured' to make it permanent. Fortunately, it's a very simple process in a home oven.mini oven

CURING INSTRUCTIONS - FIMO polymer clay

  1. Preheat oven for twenty minutes to 110 C or 230 F *.  The preheating means you won’t get any huge spikes in temperature that might ruin your piece.
  2. Place the piece on a flat baking tray or at the bottom of a roasting tin. I usually put a bit of greaseproof paper on the tray, but foil or paper will do. **
  3.  It is good practice to ‘tent’ your piece with foil or to cover the roasting tray you’re using. This protects your piece and contains some of the curing smell, and may prevent whites from yellowing if your oven is a bit too hot.  But it will probably be absolutely fine without it (I quite often don’t bother).
  4.  NB: The piece will be fixed in the shape it is baked in, so make sure it is how you want it before you put it in the oven.  For instance, if you've made a pendant, make sure it's laid flat without lumps and bumps, jump rings in the right position, and no edges curling up etc.
  5.  Cure the piece for at least 30 mins, and then either remove it from the oven or leave it to cool down in there. Fimo smells a bit when curing, but the fumes are non-toxic and won’t hang around.
  6.  Temperature is more important than time, as long as you cure the piece for at least 30 minutes. My experience is that if you under-bake (either by time or temperature) the piece will be very brittle and easily broken. If you get the temperature right, you can leave the piece in there for hours without any harm coming to it.
  7.  Don’t let the temperature go above about 135 C / 275 F because any white / pale coloured clay will start to go yellow, which will ruin the look of your piece.
  8.  If the oven goes above 150 C / 300 F the piece will start to burn and you don’t want that - it smells horrible!  If you do accidentally burn Fimo, open doors and windows and leave the room as the fumes may be bad for you (you won’t want to hang around anyway)
* Gas ovens
I don’t have any experience of using this type of oven with Fimo. Technically 120 degrees is ‘gas mark ½’ which should be correct, but just to be on the safe side (to avoid the possibility of underbaking) I would opt for Gas Mark 1 (which is supposed to be 135 degrees C) for 30 minutes.  Or somewhere in-between if your dial allows it. Definitely tuck silver foil around your piece as this will protect it to some extent if your thermostat isn’t very accurate.

 ** Made beads?  Curing beads on a flat surface will leave a shiny spot where they’ve been in contact with the tray. You can make a concertina out of thick paper or card and rest the beads in the folds of the concertina while baking to avoid this. Or you can just enjoy the variation…. up to you!