TM02     Ceramic Properties

 When assessing the commercial viability of raw materials supplied into the ceramic industry, certain properties are useful, depending on the intended production process and urgency of the results.

 Ceramic properties of interest include: -

Open cast coal extraction sites which have seems of fireclays between subsequent coal seams require very quick results due to the urgency associated with extracting the coal. The site needs to know if the fireclay is acceptable, ideally within a day. Acceptable fireclays are stockpiled after preliminary testing, unfortunately a significant number of seems are put to waste.

One of the quickest methods to achieve an indication of material quality is by forming a clay slab to a soft mud consistency and firing it to the appropriate temperature. This gives Wet to dry shrinkage, Dry to fired shrinkage,

Wet to fired shrinkage, and Fired Colour.

Simultaneously, both carbon and sulphur analysis can be carried out. Clays with less than 1.0% carbon and 0.15% sulphur tend to be useful for heavy clay products. If the material is to be used for whitewares, including sanitary ware and glazed tile manufacture, then clays need to have around a tenth of these values.

If raw materials contain lime (Calcium Carbonate) with a particle size greater than one millimeter a condition known as lime blowing occurs in the finished product. Lime content can be measured using chemical analysis; However, more appropriately there are two fairly quick tests which assess the raw materials for lime likely to cause lime blowing. These tests are geological lime test and the lime index test.

For more detailed accurate analysis of ceramic materials, the clay can be formed using mechanical methods which achieve a more dense test specimen, which tend to give results closer to the finished ceramic products. These methods include lab pressed tiles, either by fly-press or hydraulic press and extrusion.

Samples made in this way are suitable for: -

If the extrusion technique is used the resulting bars may be tested for both green and fired modulus of rupture which gives an indication of both green and fired strength. Bars may also be fired under load to give an indication of the firing range for that material. Extruded solid cylinders may be used to assess thermal expansion characteristics.

Applying the analysis of raw material results to ensure good finished products tend to be carried out by our customers, although we can offer constancy utilising over 60 years of combined experience in the industry of our staff.