First consideration you need to think about when you
discover glass stuck to an element is the nature of the metal of the
elements. Once fired, kiln elements
become brittle. This means that they are
likely to break if disturbed when cold.
So, you need to make sure you absolutely must do something to rescue the
kiln. It may be that you can just leave the
stuck glass alone. Where the glass is,
and how much of it, is stuck to the elements is important when considering what
to do.
Where
This brittleness of the elements means that the location of
the glass in relation to your firings needs to be considered. If the glass is on an element below your
normal firing position, you can think about just leaving it. This applies to glass stuck to the side
elements too, unless you are in the habit of firing very close to the side
elements. The heating elements of the kiln form an external layer of
oxidisation that protects the inner metal.
This means that small amounts of glass will not affect the operation of
the elements, nor your future pieces.
If the glass is stuck to top elements, you are likely to be
more concerned about future drips of the glass onto your future work. The glass is not likely to become hot enough
to detach or drip onto your work except at extended full fuse or casting
temperatures. This means that you can
observe the progress of any possible drip at each firing and only remove the
glass when it begins to begin to hang down from the element.
How Bad
How much glass is stuck to the element? Normally, if it is only a small amount, it
can be left. Ceramics kilns often have a
bit of glaze (a glass carrier of the colour) stuck to the elements and continue
to be fired for years without damage.
If there is a lot of glass stuck to the elements you will
need to remove most of it to avoid dripping onto future work.
Methods of Removing
In most cases where there are significant amounts of glass
stuck to the element, it is on the brick or fiber lining of the kiln too.
My recommendation is to heat the glass just a few
centimetres from where it is attached to the element. Use a hand-held blow
torch to do this. When the glass is red hot - enough to begin moving - you can
pull it away between the lining and the element with long handled tweezers. Do not attempt to pull it off the element
right away. You can later chip the glass
off the lining without damaging the element as the connection is separated.
As the element has begun to be warmed by the heat used to
separate the glass on the lining and the element, you can continue to warm the
element, moving the torch in a slow waving motion at least 10cm each side of
the stuck glass. When the glass and
element are red hot, you can begin to pull the glass off with long handled tweezers,
bit by bit. Keep re-heating the element
and glass as much as necessary so the temperature does not drop below cherry
red. This ensures the elements continue
to be flexible and will not break.
Of course, glass can be melted onto its kiln furniture and there are different considerations for those circumstances.
I appreciate the thorough research and clear explanations in this post. Your passion for the subject shines through, making it a pleasure to read.
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