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polymer clay help please!

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  • polymer clay help please!

    I know this gets asked over and over again but I would like to clarify re the cooking of Polymer clay - specifically fimo.

    My children are making little pendants etc for their Nan's birthday today (not last minute at all!!), however I have tried cooking some tester clay at 130 degrees following advice from the internet for 20 mins. I have then tried to do the bend it without breaking test and it broke! So believeing that this means it is undercooked I put it back in for another 10 mins tried the test again and still broke.

    Can anyone tell me what the problem might be. I think that I read somewhere that you cannot cook it for too long but if it breaks easily it is undercooked.

    What is more important? The cooking time or temperature?

    Pleeeeeeeeeeaaaaaaaaaaasssssssse help. The girls get really upset when their creations break in half.

    Claire x

  • #2
    I always cook my fimo at 110 (it did used to be 130 but changed some time ago).

    I also cook my pieces many times over and don't worry about burning as long as you keep it on the same temperature.

    Not sure what you mean about bending once its cooked mind you, unless you are talking about eraser clay?

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    • #3
      I read somewhere that once cooked it should be flexible and that you should be able to bend it into a u shape without it snapping. I presume that this is once is first removed from the oven.

      The prob that I have found is that if the girls make a snake (for example) it snaps easily once cooked and cooled. Also if they drop their objects they break easily. Obvoiusly beads are more robust due to the spherical shape.

      I have just tried again and it is still snapping. AAAAaaaaggghh!


      • #4
        It could be several things.
        1. clay too thin. If the clay is rolled to thinly, it doesn't withstand bending.
        2. It shouldn't bend too much, but should be slightly flexible.
        3. you might not be conditioning the clay enough first. The clay somtimes begins to seperate in microscopic texture and you need to knead a little before using it.
        4. when the shapes are made, you might be leaving small fractures or splits that are then becomming the weak points.
        full time mum and very very part time crafter.


        • #5
          So it wont be cracking because it is under or over cooked then you think?

          I cant think that the fragility is due to it being underworked (They work it until an inch of its shelflife).

          I understand what you mean about the weak points but again they dont necessarily break at the joints.

          I am going to go and cook it again - and see how we go this time!!

          Thanks for your help so far - any more thoughts would be good.

          Claire x


          • #6
            Some of my fimo or sculpy that i've had for like a year went brittle, took ages to work it so it was supple enough to make stuff and then after baking most of the things broke. So make sure its all smooth and nice before making things first of all.
            I've noticed when things come out of the oven they are a little bendy but i think they would break if you bent them at that point anyway if you used a little too much pressure... I have also found the only clay i've managed to burn was a translucent sparkly one which went kind of brown. maybe cooking them at a lower temp for slightly longer would help. i'm sure i put mine in for 25-30 mins...
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            • #7
              Don't bend it when it comes out of the oven, it is still hot and at it's most fragile
              Put the items straight into a bowl of ice and water when they come out of the oven
              This is meant to strengthen them further
              A little trick I have learnt, when making small things which can be breakable, add a drop of liquid fimo to the normal fimo and work it in really well, them make the pendants
              When liquid fimo is cooked it is extremely strong, so adding this will strengthen it
              Handmade Sock Monkeys, cats and animals


              • #8
                Thanks for that - I didnt know that you could get liquid fimo - duh!

                Can you use that to help bond joints together in the same way that you would use a 'slip' in clay?

                Claire x


                • #9
                  Yes, I primarily use the liquid fimo for joining, and I also use wire for extra strength too
                  It can be used for so many things, like transferring images (though I haven't tried that yet), fairy wings, mermaids tails etc
                  but it gives you some great tips on the leaflet that comes with it.
                  Hope that helps
                  Handmade Sock Monkeys, cats and animals


                  • #10
                    Much depends on the brand of polymer clay you are using. There are some formulations that are stronger and more flexible (Fimo Classic, Premo, Cernit etc). Other formulations tend to be more brittle (Fimo Soft, Sculpey for example.)

                    Fimo bakes at 110. The bad news is that even properly baked polymer clay will break if you try to break it. . Even the strongest clays will do this, so you need to design with the materials own strength in mind. I make solid beads from Fimo and they will outlast my ceramic or glass beads for centuries I reckon! I have driven oven them, hit them with hammers - you name it. All in the name of science I might add. I am not just nuts or something

                    But I would never consider making fine petalled flower beads or delicate jewellery bails from polymer clay and expect them to hold up. It just isnt in the nature of the material anymore than I would make a paper umbrella. Doesn't mean that paper is useless just because we cant make umbrellas from it.

                    So chances are, you HAVE baked your clay perfectly well. Much of the infomation you find on the internet will relate to previous polymer clay formulations which were often a little more flexible when baked as they used different ingredients that are now banned by the EU.

                    The key with pendants is to make them at least 3-4 mm thick. If you are using Fimo then baking thinner pendants at 130 rather than 110 does make them stronger and more flexible.

                    The other issue to consider is - is the oven temperature accurate? The thermostats on most kitchen ovens really are not that accurate and with Fimo, just a difference of 10 or 20 degrees can make all the difference. The best thing is to get an oven thermometer and check that the temperature you are baking the pieces at really IS 130 degrees firstly.

                    If you still have problems, consider maybe making the pendants thicker or even using an armature. I sell a Metal Base kit in my store that is useful for these sorts of projects - where you can laminate the clay sheet to a metal backing, allowing you to give the pendant a little rigidity and keep its thinness.

                    Ultimately though, I think polymer clay works best on projects that have some dimension to them (solid beads, models etc) than things which are too flat or thin.

                    This is not meaning to be detrimental to polymer clay. Far from it, I love the stuff! But if you had a thin piece of wood or glass of the same dimensions, chances are they too would snap if you tried.
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                    • #11
                      Thanks Emma,

                      My oven is pretty rubbish admittedly! So I used an oven thermometer. I had to put the gas mark to 1 and then bake on the lowest shelf. From what you are saying it sounds like it is better to bake at a higher temperature than too low. As you mention baking thinner pendants at a higher temperature for stability and flexibility. I am also still confused if you can bake it for too long. I had a crafty friend here who suggested that I am baking it for too long.

                      Just can't get my head around it. You do see people doing intricate little flowers with it, with tiny petals - do these not just break off?

                      BTW Emma I love your beads and site.

                      Thanks everyone for your help. sorry if I am sounding soooo dumb on this matter.

                      Claire x


                      • #12
                        There is nothing dumb about your questions - far from it!

                        I have to admit, I have no experience of cooking fimo by gas oven (well I did it many, many years ago, but forgot the details, gas mark etc)

                        I personally have found that Fimo does need to be baked pretty close to the 110 recommended temp. It took me a while to get used to the new formulation actually because of this, but I love it now.

                        For me - solid round objects were prone to cracking if I bake higher than 110 degrees. But flat sheet objects (pendants etc ) were fine and actually way more flexible at the higher temp of 130.

                        I have to stress though, I have talked to a lot of other clay artists who bake all their fimo at the 130 temp still without any problems - so its a mystery why it doesnt work for me that way!

                        As for Fimo Flowers - well, I have mixed feelings. If used for things like wedding cake toppers etc, then I think Fimo is great. My mum is a caterer and creatings beautiful flower displays for cakes and has on occasion used Fimo and its great. But if you are making jewellery that will take everyday use and abuse, those flower beads need to be designed accordingly - thicker petals, less protrusion from the body of the flower etc.

                        I have seen some fantastic flower beads made that seem very robust, and still look dainty. So its just about working with the material and designing with strength and structure in mind.

                        The thing with baking Fimo though - and all aspects of Fimo actually - is you need to be a little bit of a mad scientist. So try making a few test tiles and test balls and bake a little higher and see what happens. Do they get stronger? Do they exhibit cracks? An afternoon doing that will tell you more than any book or website can about baking Fimo. Because you are testing your own oven, your own method for condition and using the clay etc. By doing that, you will work out the best temp for baking your clay work.

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