ZALT@aol.com on sun 9 feb 97
Hi; Just getting over the flu bug. It was one H.ll of a cold.
You could see from the last post, that we are getting closer to determining
what not to charge for our work. This post we will discuss some methods on
determining firing costs.
You may recall from earlier posts, that I mentioned that some figures will
remain fairly constant even though they appear in the VARIABLE COSTS part of
the computation. One of these constants will be the firing charges for our
mugs. The figures will remain fairly constant providing our mugs remain
constant in size and providing we fire a similar schedule each time. Firing
normally consists of two schedules. Some people may schedule a third firing
for overglaze or luster application but for our example we will stick to the
standard, two firings. Determining firing costs for the bisque is
relatively simple. You simply count the number of mugs it takes to fill the
kiln . If you cannot fill the kiln with mugs and want to complete the firing
with other pieces then find the percentage of the kiln space taken by the
mugs and use this figure when calculating the cost. Do the same computation
when you load your kiln for a gloss firing. Record the number of mugs that
you can place on each shelf. I have established my bisque firing to be
between 110 and 125 mugs and my glaze firing to be approximately 88 to 100
We must record the electric meter reading at the beginning of the firing and
again at the end of the firing. We then figure out the difference of the
two meter readings in order to determine the electric kW consumption.
Finally we will multiply our kW consumption by the Hydro cost per kW, in
For the sake of discussion we can say that when we fire 125 mugs in a cone
zero-six bisque, we use five units of electricity at $1.15 per kW unit,
including tax. The overall firing costs would come to $5.75 or approximately
$0.05 per mug. A cone nine glaze firing of 100 mugs consumes approximately
12 kW of electricity. This equates to $13.80 per kiln of mugs or
approximately $0.14 per mug. We combine the two firing figures and arrive at
a total firing cost of $0.19 per mug.
Remember to read the meter before and after each firing to determine your
firing costs. Keep your firing costs separate from your day to day operation
as they are calculated as a VARIABLE COST . The day to day electricity
consumption show under FIXED COSTS. Learn your kiln capacity for full loads
and calculate part loads as percentages of your kiln capacity. For example,
If you have only 50 mugs to fire then they will use approximately one half
of a full kiln.
Glaze costs are another item that must be calculated when determining the
production costs of our mugs. Finding them can be a bit complex especially
if we glaze numerous different size pieces from the same bucket. For our
discussion we will determine our glaze recipe size; cost the recipe; mix the
glaze to a standard specific gravity, and then weigh the entire batch before
glazing our mugs and again after glazing them. We will find the difference
in weight of the two figures as a percentage of the original weight and
multiply the results by the cost of the entire glaze batch. Dividing this
number by the number of mugs glazed will give the unit glazing cost..
For example, we make a glaze batch that costs $3.20 to produce. We record
the specific gravity and then weigh the entire batch. Don't forget to take
into account the weight of the glaze container and adjust the weights
accordingly. We then glaze our mugs. In this case we can glaze 20 mugs. We
then re-weigh the glaze batch again . In our example we find that we
consumed 50% of the entire batch. Multiplying the cost of the entire batch
($3.20) by 50% we can determine that $1.60 worth the glaze was used.
Dividing this figure again by 20 we calculate our unit glazing cost to be
$0.08 per mug.
We should remember that some glazes are very inexpensive and the cost will be
negligible. However, if we work with material such as Albany slip and
cobalt, our recipe may be very expensive. It is therefore, important that
we calculate our glaze costs every once and a while to ensure we know what
our mugs costs to glaze. Once we establish the cost for a specific glaze
batch we should record the information in our notes for future references.
Another important point to note here is that by knowing the specific
gravity of our first glaze dip we can approximate future glaze costs without
having to go through the weighing process. All we have to do is ensure the
glaze batch is at the same SG.
So we will close another post by summarizing our findings to date:
Fixed Costs $38,350.00
Material costs clay per mug $0.45
Transport costs clay per mug $0.09
Glazing cost per mug $0.08
Firing Costs per mug $0.19
Total = $0.81
Next post we will tally up. See you then.
For those who have just joined this thread: If you want copies of pages one
through six e-mail me.
Terrance F. Lazaroff
St Hubert, Quebec, Canada!!!!!