|Monthly Tech-Tip |
If you are a potter and have gotten away with pushing the limits in your process for many years there will eventually be a day of reconing. It is better to understand why you do things the way you do and be ready to adjust.
For every mile of highway there is two miles of ditch! If we compare on-going pottery production to a highway, then many of us spend some time in the ditches with troubles. It is hard to accept a kiln load of warped, bloated, dunted or crazed ware or a drying rack of cracked pots.
I've seen some potters cry and others go bankrupt when unable to solve a problem. That's why I'd like to promote a middle-of-the-road approach to production practices and an understanding of the trade-offs of your process and materials. If you think you have a process or a clay body that enables you to break the rules, think again. Materials, bodies, and your process vary, you need to have some margin-for-error to prevent problems. THE NATURE OF CERAMICS IS THAT IF YOU DO YOUR BEST AND YOUR SUPPLIERS DO THEIR BEST THERE WILL STILL BE PROBLEMS.
For the sake of argument, lets assume you're in trouble. You think the clay is the problem. You need to solve the problem. Let's consider some viewpoints that can get in the way of doing that:
I've always done things the same and now there is a problem, it is not my fault: Have you really always done it this way? Are there changes you have overlooked? Is the way you have always done it the best way? If you have been "driving on the shoulder" by taking shortcuts in the forming, drying or firing process then is being in the ditch a surprise? Is it possible that no supply company to deliver the kind of consistency that your "push-the-envelope" process requires.
We are too busy, we don't have time to change our process: By understanding every detail of the process and optimizing accordingly industry has figured out how to fire ware in less than a hour cold to cold. Maybe you could analyze your situation and solve the problem and cut time. Clay manufacturers are happy to help. Call them early. Remember, each clay has a complex personality. It is often better to work out the problem then start over with a new body. However be ready to switch if an evaluation demonstrates the need.
I'll worry about making the ware, the clay manufacturer can worry about keeping the clay consistent: First, are you paying due attention to 'making the ware'? What condition is your kiln in? Does it fire evenly? Do you really know what temperature it fires to? How do you dry ware? Do you stress test your glaze to make sure it won't craze and pieces won't crack on sudden heating or cooling? Second, how trusting are you? At Plainsman Clays we've been burned enough times that we cannot afford to take this view with our refined clay suppliers. We do test each clay body run for many physical properties and compensate recipes to smooth out variations. But we do not test for things like thermal expansion, ultimate particle size, chemistry, and mineralogy. If you like to run your business on the shoulder of the highway, variations in these could put you into the ditch.
I don't need to know that technical stuff, just give me a good clay and glaze recipe and I'll do the rest: How do you know what to do in the event of a problem if you don't know technical stuff? 'Doing the rest' involves dealing with variations in your process.
I've been potting for 20 years, I know what I am doing: Old habits die hard and can bring trouble. No matter what experience you have, the wise course is to be open to logical reasoning on why you should do something differently. Depending heavily on a traditional but shakey technique will bring a day of reckoning.
So-and-so said this is my problem: Did they explain logically why?
This body is crazing my glazes: Glazes craze because their thermal expansion does not match the body. You have to change one or the other. Firing slower just hides the misfit problem, time will display it. There is only one fix: adjusting the thermal expansion of a glaze. It is easy. You should be using an adjustable glaze so you can fine tune on an ongoing basis. You should be doing ice-water:boiling-water testing. Check digitalfire.com for more information.
Do you understand the tradeoffs of your body and process? For example, vitreous bodies tend to warp. Vitreous stonewares may tend to bloat on overfiring. Highly plastic ones tend to crack on drying. Porous functional ware bodies will leak and break easily. Low-silica or high feldspar glazes contribute to crazing. Misfitted glazes severely impact ware strength. Etc. Understanding your clay body and being in contact with the manufacturer is good. Plainsman Clays, for example, publishes very detailed body data sheets at its web site at www.plainsmanclays.com. You are free to email any time about a body problem, don't suffer and suffer without seeking help.
We are all going to weave on the one-way highway of ceramic production, but if you are near the middle you will stay out of the ditch.
|By Tony Hansen|
Follow me on