A number of us with kilns are sometimes asked to fire a piece or several for someone. The question of how much to charge – if anything – quickly comes to the fore.
There are several considerations if you decide to charge - and I think you should. As I go through the cost elements, I include a worked example.
This is one of the elements least considered in costing a firing. You already have bought the kiln and so it seems like you do not need to consider that cost any longer. At the least, though it is a variable cost – the cost is related to the frequency of use. Fewer uses leads to higher costs for each firing and vice versa.
You can use a discounted cost or a replacement cost for your calculations.
I take the cost of the kin and discount if over five years. Divide the purchase cost by the number of firings per year and you have the cost of each firing spread over five years.
So if the kiln cost you £5,000 – enough for a metre square kiln - and you fire on average 3 times per week this gives 156 firings per year and 780 over the discounting period. This means the depreciation cost of each firing is £6.41 per firing. Of course, if you fire more frequently, the cost per firing comes down.
You can also consider the replacement value after 5 years. If you assume the cost of kilns will increase by 5% per year then your replacement cost will be £6077. So the replacement cost of each firing would be £7.79. This replacement cost is of course a kind of unseen cost of using your kiln. It needs to be accounted for so you can buy a new kiln when you need it.
These considerations show the use costs of the kiln are between £6.41 and £7.79 per firing even before you consider the material costs. For ease of the example, lets round this to £7.10.
To the replacement cost you need to add the electricity cost per firing. A 30kwh three phase kiln can use around 50kwh for a full fuse firing. If the electricity costs 0.15/kwh, the electricity cost of firing is £7.50. This increases the cost to £14.60
If you are covering the shelf with Thinfire, the additional cost will be in the region of another £7. This brings the cumulative charge to £21.60 per firing. Even if you don't use Thinfire or other ceramic fibre paper, you should add 10% for the materials used, but are too small to be accounted for separately – £2.16 – giving £23.76.
Then add time that you spend. If you are placing the material in the kiln, or programming the controller, the time that takes needs to be added. If you charge your time out at £20 per hour, you may use a large part of that hour just assisting the person. If you are placing things for the person, the time used will increase. Assume all you have to do is prepare the kiln and shelf and programme the controller – this will take the best part of an hour, so add £20 to the charge. You now are up to £43.76 in costs.
Then add opportunity cost - the price you put on the time you couldn't use the kiln. If it is not putting you out, the opportunity cost is £0. If however, you could have been doing something else in it then you need to charge for the disruption. This is flexible, but might be the cost of one kiln firing. If it is the cost of one firing you add £23.76 giving £67.52.
The firing charge
The minimum you should be charging for others to use your kiln is £43.76. If you consider the disruption and opportunity costs, the price should be at least £67.52 in this example.
What this means for the pricing of your work
These considerations make for an apparently high charge, but shows you what your firings cost you and what should be factored into your charges for kiln formed materials. The minimum you should be adding in this example is £23.76 for each firing for your own work. If you could get four pieces in your kiln and need a fuse and slump firing, each piece has a firing cost of £11.88 (23.76 * 2 / 4). Then you need to add glass costs, time and profit to get the wholesale price. Double that for the retail price.
Fusing is not cheap.
Fusing is not cheap.