Ceramic Tests Overview

Every ceramic production facility should have some sort of materials, body and glaze testing program in place. Amazingly, many large factories have little or no testing! Then one day the kiln operator notices a large number of cracked, warped and off-size items and every one in the plant is blaming him. Likely the real causes are in a number of places earlier in the production. This underscores one of the primary reasons for testing and quality control: to establish specifications and to set off procedural alarms when test results fall outside those specifications so problems can be identified before a product goes to the next step of production.

It is not easy to know where to start when it comes to setting up a testing program. The huge array of ASTM test procedures, their complexity, test equipment requirements and their expense intimidates many people (try finding tests for ceramics on their website to see what I mean). These tests are great if you want to generate numbers that can be compared across an industry (for data sheets for example). But if you only need to do testing within your own facility to determine product consistency, a simpler and more accessible approach is better. Of course, either way, there is the problem of dealing with the mountain of data that is generated by a quality control program. The is where good software comes in (e.g. Digitalfire 4Sight Server).

Where do you start? Think of it this way: What physical properties of your bodies and glazes are important to maintain and are signals of changes you need to be aware of. For plastic bodies likely you want to monitor particle size distribution, drying shrinkage, water content, fired shrinkage and fired porosity. Two tests (SIEV and SHAB) can give you all of this information. You might like to add the DFAC test if you are using a plastic forming body. For casting bodies you must also watch rheology properties (use the RHEO test). For productions glazes use the GLAZ test to maintain the slurry (others will of course to need for color, surface, hardness, expansion, etc). Remember, we are talking about where you start here, of course there is no limit to how fancy a quality control program can be.

Tests in this database are defined as Multi-variable or Single-Variable. Single-variable tests are used to define a value for a specific property. For example, the melting point of a material is specified under the MLPT test and simply appears on pages as a label and a value. Multi-Variable tests are where data is being collected and measured over time and the system compiles and computes results and displays them accordingly. Data values for multi-variable tests are recorded with the Sample/Test/Specimen/Variable to uniquely identify them. For example, in the SHAB test you collect the dry length, fired length, fired weight and boiled weight for a number of specimens of a particular clay body run and the system generates a chart showing the data, the calculated dry and fired shrinkages and the porosity.

By Tony Hansen

See Also

  • Porosity

    In ceramic testing this term generally refers to the pore space within a fired clay body. It is measured by weighing a specimen, boiling it in water, weighing it again, and calculating the increase in weight (thus it is also known by the term absorption). As ceramic clay bodies vitrify in a kiln the...

  • Low Budget Testing of the Raw and Fired Properties of a Glaze

    There is more to glazes than their visual character, they have other physical properties like hardness, thermal expansion, leachability, chemistry and they exhibit many defects. Here are some simple tests.

  • A Low Cost Tester of Glaze Melt Fluidity

    This device to measure glaze melt fluidity helps you better understand your glazes and materials and solve all sorts of problems.

  • The Physics of Clay Bodies

    Learn to test your clay bodies and recording the results in an organized way and understanding the purpose of each test and how to relate its results to changes that need to be made in process and recipe.

  • Understanding Thermal Expansion in Ceramic Glazes

    Understanding thermal expansion is the key to dealing with crazing or shivering. There is a rich mans and poor mans way to fit glazes, the latter might be better.

  • Firing Clay Test Bars

    Being able to make good consistent test bars and fire them in a consistent and proper way is a basic requirement of getting valid results for shrinkage and porosity measurement.

  • Are You in Control of Your Production Process?

    Potters often run operations that are on the edge of control and they tolerate production and ware problems that industry would not. However ethics an honesty with yourself will soon or later demand a better knowledge of process and materials.

  • Outdoor Weather Resistant Ceramics

    How can you be sure that the porosity of your fired ceramic ware is low enough to prevent freeze-thaw breakdown in the winter?

  • Firing Shrinkage

    As kiln temperature increases bodies densify (particles pack closer and closer). As temperature continues to rise, some of the particles begin to melt and form a glass between the others that pulls them even closer. Some of the particles shrink themselves, kaolin is an example (in the raw state part...

  • ASTM Ceramics and Glass Testing Standards


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