When you have many hours of work in the oven, why take chances?

How many times have you heard someone tell about all the hours they have put into a piece of work to have it break when they were sanding or finishing it.  It is heart-breaking to put all those hours in to have that happen.  A tiny scrap of polymer clay can save you a whole lot of grief!

When I cook my polymer clay work, I use the highest temperature possible to ensure strength, tent it with a piece of card stock it to prevent scorching and include one or two small clay cones (less than an inch long) so I can test the strength of the baked work.  After the baked clay has cooled, I try to break one of the cones.  I do this by pressing the point against the table. It should bend but not break. If the cone breaks, it has not been baked long enough and needs to be baked a second time to strengthen the finished work. You should also check your temperature to see if it is hot enough. Use an internal oven thermometer for this – don’t trust the dial on the oven because oven temperatures vary.  If the point of the cone bends but doesn't break then the work is strong and tears are avoided.

Some clays are stronger than others.  Sculpy III is more rigid and comes in great colours - I would not recommend it for delicate items that will be worn or used every day.  Fimo, Premo and Kato Clays are strong enough for functional items but there can be differences from colour to colour.  The cone is always a good idea to detect the changes.

Some pieces require a number of cookings. Each time I include a cone to make sure that the cooking time and temperature has been sufficient .  If you are working on a large piece in a large oven it is wise to test different parts of the oven for temperature variations. When you are using an oven for the first time strategically placing cones around the interior of the oven.  A test cooking can let you know a lot about the potential of the oven.

In spite of the fact that I am in love with my new Breville Oven that delivers lovely, even heat, I still use a cone and once in a while I still need to cook work a second time especially with dark red items. I do not know why this happens only with red. (Fimo Classic number  #23, my favourite colours, requires extra care to make sure  it is cooked long enough and hot enough to be strong.)

Well, there it is, use a tiny amount of clay and save yourself breakage, tears and money. Just pinch off a little clay from whatever you are working with and make a little cone. The clay can be a mixtures of colour, just a little bit that you are going to use as backing or the core of a large bead. Come on, now you can spare that much clay to save your friend from hearing your weep about a broken piece.

For those of you who are still worried about throwing away even a little clay here is one of the things I have done with some of those little fired cones. I have trimmed the bottom off the cone to make them sit nicely then set them up right in an uncooked disk of scrap clay. I brush the disk with a little liquid polymer clay first to ensure good bonding. Cook this to cure the disk – using a cone for testing of course. You have made a great little soap saver that allows soap to dry out and therefore last longer. I also use one of these to dry out my deodorant stone. There are many other uses – I’m sure you can think of some.


Nola said...

deaGreat article Joan...I learned a lot!!!

Lawrence said...

Great idea Joan.
Potters always use cones in our kilns when firing so why not for polymer clay.

Karma said...

Might want to make them a little bigger and use those pointy contraptions for drip trays when curing resin or drying clear coats on a cab. Great article, though. I have had several thin items break on me, mostly on glass polymer covered votives. Thanks for the idea!

joan tayler said...

Thanks for the great suggestion.

Sally said...

I am pulling my hair out! I've cooked and recooked and still breaking. What is the highest temperature you would bake Premo? I'm up to 300 deg and it still breaks... thanks!

joan tayler said...

There are two or three possible other reasons for breakage. 1.) Your oven is not as hot as you think. A remote possibility but check with an oven thermometer to eliminate the possibility. 2.)Perhaps some Sculpy III or other weaker clay has been mixed in with you clay. 3. If your clay is conditioned thoroughly, Like 20 0r 30 times trough the paste machine or the equivalent it should be stronger.
I hope this helps. Report back please.

Sally said...

Thanks, Joan... I think maybe my clay has some Sculpey mixed in. And it might also be that I'm expecting too much out of my work. I'm definitely going to do the cone trick as I've checked the temp in my oven a zillion times. Thanks again for your quick response! I'm going to go find you on Facebook.... :-)