Friday, April 18, 2014

Four Tips For Sintering Metal Clay in a Kiln

When firing your clay in a kiln, there are a few things to think about:
  • Support
  • Placement
  • Heat
  • Time

Placing the item on a fiber blanket and pushing the blanket up under the unfired piece helps support it. I like to place my sterling (for the first firing) and fine sliver pieces in a fiber bowl with vermiculite to support them.

Vermiculite Bowl & Fiber Blanket

If I have an item with a wide side, that side is placed perpendicular into the vermiculite. This helps avoid sagging because gravity has less of an effect on it. Place the bowl raised up off the kiln floor so that the heat can move around the whole bowl. This keeps the bottom of the bowl from being cooler. If you don’t use a bowl, then raise the kiln shelf off the kiln floor and support the items, if needed, using fiber blanket or thick fiber paper.

Always notate the locations of the kiln’s heating elements. Most front loading kilns do not have elements in the door, so the front of the kiln will be slightly cooler than the back. Top loading kilns tend to heat more evenly. If an item has a stone or sterling silver embeddable, place them towards the cooler area of the kiln. If there are sterling silver embedded objects then don’t heat higher than 1200 degrees, but heat longer to be certain they attach.

I have discussed the importance of testing your kiln's temperature at different degrees in the past. I cannot stress how important this is. Tested kilns have shown that some kiln's temperature is up to 10 degrees higher than it's readout suggests.

Lastly, there is the issue of time. Sintering time is a constant variable, depending on the circumstances. For example, there may be time constraints due to a classroom situation. It is always best to sinter the metal clay for the longer recommended period of time. This allows the molecules to soften and attach to each other. If attaching pre-fired items together, heat the piece to as high a temperature as is allowable for the metal and for the longest recommended time.

Until next time, have fun claying around!

by Janet Alexander 
Technical Adviser


Kris Kramer Designs said...

Have you ever used Alumina Hydrate for a support medium? I love it. I bury my prone-to-warpage pieces in it and they come out well. I wear an N95 mask when brushing afterwards.

Janet Alexander said...

HI Kris,
No, I haven't used Alumina Hydrate. Tell us more about it!