For my 2016 Polymer Clay Challenge I have decided to make a vessel each week. I’m planning a wide range of objects from inros to bowls to covered jars so my first dilemma was deciding where to start!
Since I had a sheet of mokume gane lying around (as one does), I decided to start by covering a jar you either love or hate ;). It was already dark glass so I didn’t feel too guilty covering it with an opaque sheet of polymer clay.
Green jar by Cate van Alphen
My idea was for it to look like a chunk of lava rock that had been shaped into a vase with a the sides polished off to reveal the bright mokume gane inside. Something almost completely, but not quite, unlike a bolder opal.
I started off by baking pieces of mokume gane onto the flattened sides of the jar so that it would remain smooth while I textured the black polymer clay around it. Unfortunately my simple idea soon turned into a rescue mission as one side cracked. I tried filling it with liquid clay for the next bake and I ended up with a bigger crack and another on the other side. (It’s only just occurred to me that I should have popped off the mokume gane and started again). The more I tried to fill the cracks, the bigger they got. 😥
Since this is my first jar, I’m not sure if this is just something that happens when you cover a glass jar with solid polymer clay or if it was because when I baked the patterned sheets I did a part bake as I knew I would be adding more clay and doing further curing. I do have (up to) 50 more* times to practice, but any suggestions to prevent cracks would be appreciated.
I have started a group on Flickr for Art Vessels if you’d like to join in with your own creations. It’s not limited to polymer clay either, just in case you make chocolate tea pots.
* I am determined to also have a go at making an inro before the end of the year!
Fulgorine 
It’s a stunning jar, Kate, cracks or not, and cracks seem to fit well with your idea of it being like a chunk of rock!
No idea what causes this – l’ve just had a similar thing happen when using a six-sided jam-jar as a former for a box so l want to know the answer too!
Can’t wait to see what you make for this very ambitious challenge, especially after this great start ☺
Thanks. I will try not to be too depressed about the cracks. Maybe I should have scratched some into the black too?
Not sure about that, but some black acrylic paint in the crack might be good – what do you think?
For now I’ve put it on the shelf with its back to the wall. 😀
Good plan 😌
The jar looks great, cracks and all and I agree it does add to the feel of the lava rock theme. My guess for the crack is that the mokume gane was baked so it had it’s shape and density. When you added the black clay around it, it expanded slightly when baking pushing the not quite cured mg and then caused a crack when it got cooler. I’ve done lots of bowls and vessels a couple of years ago. I made a bowl a week for the whole year and I learned a lot about clay and how it behaves. I’d be glad to help if I can. It’s a question of trial and error and seeing what you gravitate towards. I like armatures that you can take away to leave only the clay but that has it’s own set of rules. Good luck in this new venture. I’m sure you won’t regret it.
Thanks, I’m planning to have a go with removable armatures too.
Hi Cate – I don’t know anything about Polymer on glass, but thought I’d mention something the Japanese do with broken pots. They put gold on the broken edges when they repair a ceramic pot (see image attached). Celebrate the flaws! :-)EgEsther Golden
Good idea. 🙂