Friday, September 19, 2014

Testing the New PMC Flex Clay Part 1

As an early tester of  PMPC Flex, I cam to really enjoy the clay's properties. In the coming weeks and months, I'll be sharing some of my thoughts about the clay with you. For this initial post, I was asked to describe just how flexible the clay is and how long it stays that way, how easy it is to rehydrate, and shrinkage rates compared to PMC3. My results are below.

How long does it stay flexible?
What a great question. For this blog, I was asked to test the flexibility of air-dried PMC Flex clay. While looking through my test clay from a year ago, I found a large piece of clay that was in an open packet. It was rock hard dry. At least it seemed rock hard until I cut into it.
I cut it into two pieces with a razor. It sliced very easily. In fact the new sliced face looked shiny like it was wet. So I took a dental tool to see if it was soft. It was!

I then sliced off a piece and it was flexible. After a year of drying, I could still bend it without it breaking! 

Going back to the original question, I cut a rectangular piece of clay, rolled it out 4-cards thick, and  left it drying on the counter top for 24 hours. I tested it again after three days and still bent as much as it did straight out of the package. I compared it to the year-old clay and the bend I could achieve with the two pieces was nearly identical.
Please note that drying PMC Flex on a hot plate, dehydrator, or cup warmer made it less flexible. Drying the clay on a cup warmer may be good for drying rings so that they don't flex as much while finishing them in the unfired state.

Here is an extruded roll of clay bent into a curl shape without using glycerine. No cracks.

How well does it rehydrate? 
I took half of the dried ball of clay I found from last year and cut it into small pieces with a straight edge razor. I spritzed it with water, mixed it with a pallet knife, and rolled it between a plastic report cover. I repeated the process until the clay could be picked up in a flexible sheet. I allowed it to sit overnight and found the clay as elastic as the newly opened package. 

What is the shrinkage comparisons between PMC3 and PMC Flex?
I rolled PMC3 and PMC Flex to the same thickness and cut them into equal round discs.

I fired them at the same time at 1650°F (898°C) for two hours. As you can see in the photo, the shrinkage was identical.

Here are some of my initial findings about PMC Flex:
  • The length of time that the clay remains flexible depends on drying technique. PMC Flex dried on a cup warmer/ hot plate became less flexible faster than clay dried in the dehydrator at 155˚F (68˚C) for 15 – 30 minutes. Air drying allows for an even longer flex time.  For example, pieces 3-cards thick that were air dried were still are somewhat flexible 24 hours later.
  • The thicker the piece of clay, the longer flex time. After 60 minutes the 11-card thick piece of clay still mashed down and sprung back to shape.
  • I found that when drying PMC Flex in a dehydrator, the bottom surface of the clay imprinted the texture of the dehydrator. This could be a problem for an item that has texture on both sides. I recommend placing PMC Flex on something smooth until the outside layer is dry.
  • The clay stays so flexible that I became concerned about drying it in a dome. Would it loose its shape after removing it from the doming plate to dry completely? This was not the case. It kept its shape for the most part. I was able to reshape the dome after it became mostly dry.
  • While sanding the sides and insides of a ring, flexibility became a problem.  I had to take care not to ruin the ring while sanding because it wanted to flex and bend. 

Until next time, have fun claying around!

by Janet Alexander 
Technical Adviser


Roxanne Coffelt said...

Thanks for sharing this. You answered my first question, which was whether or not it could be combined with PMC3. Since they are both 99.9% silver and shrink the same amount, I'm assuming that's a yes.

My next question would be, does the flexibility indicate how dry it is? And if so, how dry does it need to be before firing, or how can you tell when it's dry enough to fire?

Janet Alexander said...

Hi Roxanne, Yes PMC3 and PMC Flex can be combined together without any problems.

Flex clay can become dry when overworked just like PMC3. I shows signs of cracking around the edges when smashed and on bends. It does however rehydrate very nicely.
I put it into the dehydrator for 20 minutes before firing. The mirror test can also be done for moisture. Place it on a mirror for a minute and then lift off. If its still moist you will see a haze on the mirror.

Marilyn Davenport said...

What are the advantages of Flex in the clay,in your experience?

Marilyn Davenport

Janet Alexander said...

Marilyn, it makes it very easy to create curved pieces without cracks. Its great for beginners who tend to allow clay to dry out. It is soft so it carves easily. It re-hydrates nicely, better than PMC3. If a piece someone is working on gets dropped on the floor there is less chance of it breaking.

Marilyn Davenport said...

Thanks, Janet. I can't wait to work with the Flex.
Marilyn Davenport

Cindy Dy said...

I enjoy most of your articles,the articles are so nice for readers.


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