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Keeping a Firing Log
In many ways the firing log is the most under appreciated
warm glass tool. All too often, the eagerness to fire overcomes the need to keep
records of the firing, resulting in loose scraps of paper with illegible
writing, disorganized rambling, or generally useless comments.
This is a huge mistake. The firing log is one of the most important tools you
have. The combination of your kiln, the glass you select, and the designs you
create are unique to you. No one else can precisely duplicate the conditions in
your kiln, so it's up to you to keep records that are detailed enough to allow
you to repeat good firings and avoid repeating bad ones.
Some people suggest that a printed firing log is best, but a simple notebook
is more flexible. You want to document all important information. Some firings
will require minimal comment, others might demand several paragraphs.
Most importantly, keep the notebook in your work area. Use it religiously and
enter essential information about each firing.
- Date and time of firing.
- Type of firing. Possibilities include slumping, fusing, kiln
casting, and fire polishing. Include information about the item being fired
(bowl, plate, etc.).
- Type of glass. Enter brand, whether opalescent, cathedral, or
mixed, and any other significant features of the glass being used. Identify
unusual textures.
- Firing schedule details. Include enough information to allow you
to duplicate this firing completely. If your kiln has a controller, write down
the program you used. Document each phase of the firing.
For each phase, it's a good idea to enter the temperature at the start of
the phase, the temperature at the end of the phase, how long it took to complete
the phase, and whether or not you soaked at the end of the phase. You may want
to enter the firing time for the phase as a length of time (e.g., two hours) or
as a rate of temperature change (degrees per hour). Use either method, but be
sure to enter the information.
As important as it is to keep a record of the firing schedule, it's even
more important to make comments about the success or failure of the firing. What
went well? What do you want to avoid the next time?
Your comments might include:
- Any cracking. If the glass cracked, indicate the kind of crack,
the number of cracks, and whether it split into pieces.
- Nature of edges. Are they smooth and well formed or uneven and
irregular?
- Degree and type of bubbles. How many, how large, probable cause?
- Placement of item in kiln. Was it centered or close to the edge,
was it closer to the elements than normal?
- Fiber paper or kiln wash. Each fires differently. If you
normally fire on kiln wash but used fiber paper this time, then record the
difference.
- Type of mold used. Stainless steel, ceramic, wet felt, all can
cause the item to behave differently.
- Uneven slumping. Did the item lurch to one side or the other?
- Any devitrification or other discoloration. Did the glass
devitrify? Did it change color or behave unexpectedly?
- Opened kiln. Document the opening of the kiln to vent during
initial heating or to accelerate cooling. Don't forget to mention how far
the kiln was opened.
- Apparent hot spots. Does one part of the kiln appear to be
hotter or colder than other parts?
- Other unusual events. Anything that happened during the firing
that seems out of the ordinary. Document power outages, earthquakes, or
unexplained results.
Rather than being a hindrance, a firing log can be viewed as the warm glass
artist's best friend. It's the place to document what happened and why.
Document your experiences and your theories.
As you become more experienced, you may find that many of your firings are
similar and require little (or even no) entries. But regardless of your
experience level, your firing log can be used as an invaluable tool in helping
you learn and document the intricacies of your kiln and the glass you use.
Click here for a look
at a sample firing log.
Click here to
go to the final part of the tutorial.
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