Friday, December 6, 2013

Don't Go Off Half Baked

If the cone breaks you should cook your piece again
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.


This was first published and a magazine article back 2011 but since it is important and it was not in my blog I am including it now.

6 comments:

Genevieve said...

I've used a thermometer for a while now too and would never bake without one.
I hadn't though of using cones though. Do you make the cone as thick as the thickest part of the clay you're baking?

Stories They Tell said...

What's the model number of that Breville oven you have? I'm assuming it's a convection? I've been looking for a larger oven now that I'm teaching home classes, although the Amaco ones I have do very well. Thank you.

joan tayler said...

Answers to Questions

cones - I make the cones tiny. I am concerned with the thin parts breaking and the general bend-ability of the piece, if the piece is large I would be cooking it much longer but I would still include a cone.

oven - Here is the link to the Breville oven the I have.

http://www.breville.ca/the-smart-oven.html

You will be able to get all the specs there.

jana roberts benzon said...

This is a great post! I am always harping on "hot baking", and so appreciate you sharing this information. I will only add that some of the clay brands do not list accurate baking temperatures and baking times on their packages. I'm not sure why, but do have theories. Anyway, conducting the test you describe (with the cones) should be done whenever trying a new clay, as the package instructions cannot be relied upon. Thanks again for spreading the word! jana roberts benzon

3circlestudio said...

Thanks so much for this post. I have been using the cones for about a month. I bake in a round halogen oven and the cones have revealed that over tenting my work prevents the heat to reach proper temperature in the areas farthest from the heat source. Who knew? Although I always use a thermometer, I rely on the cones! Thanks again. Laura

PLane said...

I just found the link to this post via Carol Simmons' pinterest board. Thanks for much for the great advice!