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Large kilns for PMC


#1

Hello,

I’ve read everything I can on this topic, but still I’m not sure if
the kiln that I might have an opportunity to buy would be a good
choice. It’s a large kiln that was used by my daughter-in-law’s late
grandmother (a wonderful woman!) for ceramics. I’m assuming she made
pottery rather than enameled pieces. I’ve read that large kilns can
have hot spots and cold spots, which could be a disadvantage for the
older types of PMC. And of course all that electricity to heat a
larger kiln, which I’m assuming is 220V. And the slow heat-up time.
My preference would be a kiln that’s versatile enough to do many
things. But my local store, Terra Firma, has a small kiln for about
$300 that would work well for most of my current jewelry efforts.

Any suggestions about either a polishing “drill” or a multipurpose
kiln would be welcome.

As always, thank you!
Lorraine


#2
But my local store, Terra Firma, has a small kiln for about $300
that would work well for most of my current jewelry efforts. 

That may be the better choice. For PMC you want a computer
controlled, very precise kiln. It needs to be able to attain the temp
and hold it, waivering just a few degrees, for 2 hours. Ceramic kilns
generally do not do that.

I like Paragon, the SC 2 or 3; you might also look into the Paragon
Firefly.

Elaine
http://www.CreativeTextureTools.com


#3

Lorraine

I've read that large kilns can have hot spots and cold spots, which
could be a disadvantage for the older types of PMC..

Most kilns will have hot spots and cold spots. What you want in a
kiln for metal clay is the ability to control the ramp up and the
firing temperature and time. For this to work well, a digital
controller is recommended. If this kiln that you are looking at will
not accommodate the addition of a digital controller, look elsewhere
for a kiln. Ideally, you want a front-loading, digitally controlled
kiln that will get up to 2000 degrees F. A top loader can also be
used, but may be slightly more limiting in the long-run for your
potential applications.

BBR - Sandi Graves
www.Beadstorm.com


#4
  1. Kilns for metal clay should be small enough so that the
    temperature range within the firing cavity is limited. Since heat
    rises, the floor area of the kiln cavity will be cooler than the
    area near the ceiling. The smaller the cavity, the more limited the
    temperature range. Kilns made for use with metal clay have
    relatively small interiors. This is good for metal clay where a
    consistent temperature is one parameter required for successful
    firing.

  2. The second parameter is the maintenance of specific temperatures
    for the duration of firing, within a few degrees. Since the metal in
    metal clay will sinter (the particles must join to make a solid
    metal object) at very specific temperatures for very specific lengths
    of time, a kiln used for metal clay must accurately maintain
    temperature for the entire firing cycle.

  3. In order to meet the requirements of the second parameter, a kiln
    for firing metal clay ought to have a computer controller. Although
    standard enameling kilns will function for firing metal clay,
    without a controller, these kilns must be monitored during each
    firing cycle and adjusted up or down when the temperature varies
    outside the specific degrees required. This is easy enough to do, but
    a waste of time, when a controller could govern the temperature (and
    duration of firing) and you could be back at your bench making more
    objects, working in the garden, playing with the kids/dogs/partner,
    etc. while the metal clay fires.

External controllers are available for kilns that do not have
built-in controllers, but are not really cost-effective compared to
purchasing a kiln, with an internal controller specifically designed
for firing metal clay.

  1. Controllers measure temperature, govern maintenance of
    temperature and govern duration of firing. Many non-metal clay kilns
    have pyrometers. These pyrometers do not have a truly readable or
    useful read-out dial. The increments between degrees are too large
    (sometimes 50 degrees), generally, to indicate the small increments
    that would mean the difference between metal clay that fires into a
    usable object, an incompletely sintered object or a lump of melted
    fine silver or gold.

If you must use a kiln without a controller, purchase a digital
pyrometer and probe. This type of pyrometer will allow you to
clearly see the temperatures within the kiln. This is not a
substitute for a controller. A pyrometer does not control, it just
indicates temperature and temperature fluctuations. With any
pyrometer you have to be present to monitor the temperature and keep
track of the duration of the firing.

Hope this helps,
Linda Kaye-Moses