Setting up a Clay Testing Program in Your Company

Description

Set up a routine testing pipeline and start generating historical data that will enable your staff to understand your source materials and maintain, adjust and troubleshoot your clay body recipes.

Article

A routine testing pipeline is essential, not just to maintaining the properties of your products, but to you understanding the materials you use and products you make from them

This page is for technicians charged with quality control, formulation and adjustment of clay bodies (generally plastic or casting) being sold for use by others. The matters discussed are also applicable to glaze or engobe production. Our method involves:

* A group account at Insight-Live.com where data is collected (this is about accumulating data and managing a lot of it).
* Insight-live is “recipe centric”, production runs and even materials being tests are initially entered as recipes.
* Testing bodies need testing below, above and at service temperature.
* Procedures are defined for testing bodies and materials being used (e.g. feldspar, kaolin, ball clay, fire clay, talc, bentonite).
* Firings each day to handle a pipeline of specimens coming from routine and development testing.
* A photo stream into the system to support measurements.
* A code numbering scheme so that every specimen can be marked and associated with its testing data.

Equipment needed:
* Internet-connected computer(s) in the lab and office.
* A test kiln (or kilns) with cones and schedules for many temperatures, staging area for specimens awaiting firing.
* A propeller mixer (lab pugmill not needed, propeller mixing and dewatering on plaster outdoes any pugmill).
* Workbenches, plaster table, tools for slabbing, cutting, marking clay.
* Tools needing for the SHAB test, SIEV test, DFAC test, LDW test.
* Melt fluidity testers.
* A flexible adhesive label maker (everything ever done needs a code number label).

Companies must deal with the reality that material supplies can be inconsistent and unreliable. You are likely reading this because you already know about that. Testing that accurately conveys body properties (e.g. fired color, fired maturity, plasticity, glaze fit and particle size distribution) enables comparing current data with historical and adjusting recipes so customers don’t see material variations.

Sampling: If you are running thousands of boxes of a run of clay it is your decision how often to sample it for testing. Likewise, when truckloads of material are received, whether each pallet needs to be tested and what tests need to be run depends on the properties the material adds to your product and your experience with its reliability.

Insight-live enables having hundreds of test bars and specimens “in progress”. With proper code and specimen numbering nothing gets lost. Side-by-side comparison of anything with anything is possible (e.g. pass runs with current, test recipes with a production run), this is the "secret weapon" of Insight-live.

A good knowledge of your materials is essential, we recommend characterization of each and testing that targets the key factors they contribute (e.g. plasticity, fired maturity, fired whiteness, thermal expansion, particle size).

Related Information

In clay body testing it is about the data.

It reveals how a 20% feldspar addition affects this clay

This picture has its own page with more detail, click here to see it.

Foundry Hill Creme (FHC) is used in North America as a stoneware body base or addition. It fires like a ball clay but it is less plastic. How much feldspar would it take to make it into a vitreous cone 6 stoneware? We fired SHAB test bars from cone 4 to 10 (bottom to top) and 10R (the soluble salts discolor it in reduction). The data collected (in our Insight-live.com group account) produces firing shrinkage and absorption data that calculates to the red columns (and plots to the blue lines). Notice how the porosity drops steadily from cone 3 to 10 (the firing shrinkage rises steadily over the same period). A 20% nepheline syenite addition plots to the orange lines. Notice 2200F (cone 6): The porosity drops from 8% to vitreous (zero) while the firing shrinkage increases 2%. The FHC drying shrinkage (the first DSHR red column) averages 0.3% lower than the mix, this is counterintuitive but a pleasant surprise. While the mix did have a higher water content (which would increase drying shrinkage) another factor appears to be how well this clay hosts the feldspar addition without compromising its own plasticity.

Setting up a Clay Testing Program

This picture has its own page with more detail, click here to see it.

It is time to start managing quality control of the clay bodies you manufacture for customers. A good program ensures that your technicians are keenly aware of the variability of material supplies (both in physical properties and simple availability). But your customers are blissfully unaware, all they will see are consistent products because of the compensatory measures you take! These measures are enabled by visibility into clay body properties that only data can give. Structured procedures, a robust code-numbering system and our onboarding help can empower your staff to get started now on accumulating a history of testing data. We are practical. The supplies and equipment you need are within the each reach of any company or even individual. This is not boring lab work, our approach makes it exciting! Your group will be able to track a pipeline with hundreds of specimens going in and analyze a river of measurement data coming out.

Links

Tests	Shrinkage/Absorption Test SHAB Shrinkage and absorption test procedure for plastic clay bodies and materials
Tests	Drying Factor The DFAC Drying Factor test visually displays a plastic clay's response to very uneven drying. It is beneficial to show the relative drying performance of different clays.
Tests	Sieve Analysis 35-325 Wet A measure of particle size distribution by washing a powdered or slaked sample through a series of successively finer sieves
Tests	LOI/Density/Water Content LDW LOI, density and water content test procedure for plastic clay bodies and porcelains
Articles	Simple Physical Testing of Clays Learn to test your clay bodies and clay materials and record the results in an organized way, understanding the purpose of each test and how to relate its results to changes that need to be made in process, recipe and materials.
Articles	How to Find and Test Your Own Native Clays Some of the key tests needed to really understand what a clay is and what it can be used for can be done with inexpensive equipment and simple procedures. These practical tests can give you a better picture than a data sheet full of numbers.
Glossary	Slurry Up The process of slurrying a clay body powder and dewatering it on a plastic slab or table.
Video	Making test bars for the SHAB, LDW and DFAC tests We will make bars of a clay body for the SHAB test (for shrinkage and absorption), a specimen for weighing wet, dry and then fired (to get water content and LOI) and a drying disk to measure drying performance and soluble salt content.
Video	Entering TestData Into Insight-Live How to enter physical testing results into your group account at insight-live.com. We will enter data from shrinkage/absorption bars, the drying factor disk and an LOI/water content tester.

By Tony Hansen
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