In these I am going to show you how to use your account at Insight-live.com to do things that were not possible until now. It is about the data. The data you let slip by in your testing up until now and the new data you will be recording as you organize that testing in a way you never did before. It is about work. If you are willing to do it you will able to learn things about your process and materials, understand them, learn to control them and take them down new roads that were not possible before.
It Starts With a Lump of Clay
How do you go about testing a new clay? I will show you step-by-step and how to document every step in your account at insight-live.com. Be warned, it is hard work. There are things to be learned and noted at every step of the way. But that is the key to success.
With clay bodies we are concerned with physics, not chemistry. We worry about things like drying shrinkage, drying performance, particle size distribution, plasticity, firing shrinkage, fired porosity, fired color, soluble salt content, fired strength, etc. These properties are not closely related to chemistry, I simply need to measure them. In doing so I am "characterizing" the material, comparing it with all the clays that I have already tested. Initially I want to answer simple questions related to how it forms, dries and fires across a range of temperatures. But later, if it has unusual properties, I am interested in what special applications it might work for.
In doing the testing I will be generating alot of data. No single factor is more intimidating to new technicians than what do to with this data, how to store it so that it can be compared effectively with other clays. An account at Insight-live.com is the answer as we shall see.
Go to Topic: It Starts With a Lump of Clay
Comparing 6 Ball Clays
Many ball clays are available and it seems that different body recipes always call for a brand of ball clay that is not in stock. So we have to get it. But how substitutable are ball clays? Of course, certain brands claim to be low carbon, their raw powder color is significantly lighter, so there is motivation to prefer them for the finest porcelains. Some claim to be more plastic because they have a small particle size, so it makes sense to use these where plasticity is most important. Likewise, we use a large particle size ball clay for casting slips. And low iron ones for the whitest bodies. This is conventional wisdom but just how valid are these ideas? It turns out much less so that I thought.
The catalyst to make me look at a detail comparison came quickly: receipt of a couple of contaminated shipments of a specific ball clay (large lignite and iron particles). The degree of contamination was ridiculous and lots of product was lost. And their testing did not catch it, we caught it and they were surprised! An additional motivation was to reduce the number of ball clays used in the production line (we were using half a dozen). We also had historical issues with the quality of another. So I questioned: Are ball clays really all that different from one another such that if I substitute one for another the body will change drastically? How really are they different? Can a knowledge of that help me eliminate some and substitute others?
As I work through this series I will refer to entering lab measurement data into Insight-live. But I will not show all the mechanical details of doing this (you will be able to find more of that in the first study in this series).
Go to Topic: Comparing 6 Ball Clays
Formulating a Translucent Porcelain
We will create a recipe for a cone 6 translucent porcelain using NZ kaolin, Frit 3110 as a flux, silica and VeeGum for plasticity. We will try to produce a compromise having the maximum translucency possible while still being stable enough in the kiln not to warp too much. This will involve making test mixes and firing test bars from cone 3 to 7 and measuring the porosity and shrinkage at each temperature.
Comparing Five Kaolins
Kaolins are not like ball clays (as we saw in a previous case study, brand name ball clays from various manufacturers are much more similar than one would expect). However, kaolins from different manufacturers are dramatically different in almost every property (fired color, fired shrinkage, drying shrinkage, dry strength, plasticity, stickiness, etc). There are many motivations to switching kaolins in body recipes (better whiteness, better plasticity, lower price, better translucency). In this article I will show you how I did the physical testing to compare these kaolins: #6Tile, Pioneer, Grolleg, New Zealand and EPK.
In the ball clay comparison I decided to flux the materials using Nepheline Syenite to get a better view of the properties they contribute to a body. With kaolins this approach is even more important. It is like comparing hockey players. While basic skills are very important, it is how they contribute to the team that is the key. Kaolins behave differently enough as pure materials that one can be quickly discouraged about substituting them in body recipes. But when mixed with a feldspar the playing field is levelled alot and we can see how they compare as team-players. The differences are easier to deal with that you might expect. For this reason I decided to also mix them with Nepheline Syenite (70:30 ratio).
More coming soon.
A Quality Control Program at Your Factory
I am going to explain why using an account at Insight-live.com to administer a quality control program at your production facility will change your life. Then we will see how to set one up and administer it using at account at https://insight-live.com.
Go to Topic: A Quality Control Program at Your Factory