In ceramic engineering, the most common method for producing ceramic components is to form a green body comprising a mixture of the ceramic material and various organic or inorganic additives, and then to fire it in a kiln to produce a strong, vitrified object. The bulk density of a green ceramic body provides valuable information needed to control the quality of a ceramic piece (after firing) with respect to its final size and the porosity and cracks in the body and is proportional to the final mechanical resistance. It is therefore important that the optimum and most accurate measurement procedures are used in determining density.
The most common method used to measure green tile bulk density has been by mercury displacement. The main advantages of this method are its ease of use and apparent high precision. Nevertheless, it has the drawbacks of being destructive, discontinuous, and manual. Furthermore, the high toxicity of mercury implies a grave health for workers performing industrial compaction controls and as such it is now illegal to use industrially in most parts of the world. This means that companies must look for alternatives to the use of mercury in tile bulk density measurement.
How the validity of the Ceramscan was measured and proven
As the existing density measurement is well known it is, of course, the method that we must successfully compare with in order to convince the industry of its suitability for method replacement. To do this, we engaged with the University of Jaume in 2018 to do a direct comparison between the two methods using the same samples. They prepared a detailed report of the findings of this research and an objective summary of the comparison between the two methods.
Their full report is available but the following bullet points and comparison table summarise their findings. Our own comments (in blue) have also been added to accompany their text.
Mercury immersion vs the Ceramscan
Comparison of the advantages and disadvantages of the two measurement methods. Stable Micro Systems response to the findings highlighted in blue.
As provided from Director del Grupo de Investigación de Química del Estado Sólido
1. The determination of bulk density by the method of immersion in mercury poses a risk to health and hygiene at work, in addition to generating toxic waste for the environment.
2. The reproducibility of the mercury immersion method depends on the environmental conditions such as possible air currents generated by the hood extractor, the environmental temperature that affects the mercury density, the dirt that accumulates in the mercury and also of the technician who makes the measurement.
3. The Ceramscan equipment, based on laser technology, is a more hygienic and environmentally friendly alternative to conventional mercury immersion for the determination of solids bulk density, the result of which does not depend on the ambient temperature or of the alteration of the measurement medium.
4. In general, when dealing with regular geometrical pieces, the Ceramscan equipment has allowed measuring with standard deviations lower than 0.005 g / cm3 in 48 seconds (0.5 mm vertical pitch and 1.5 rps rotation speed and subject to the sample holder with a Sika adhesive), the percentage of deviation with the mercury immersion method being less than 1%. However, when it comes to very irregular pieces, the deviation of both methods exceeds 2%, although they are also subject to said adhesive.
5. The reproducibility of the Ceramscan equipment is adequate when the pieces are regular and are fastened with the Sika adhesive, using 0.5 mm vertical pitch and 1.5 rps rotation speed, which, depending on the size of the piece, can reduce the measurement process to times less than one minute.
6. It is recommended that the specimens to be tested have adequate dimensions and a geometry as regular as possible so that the Ceramscan equipment measures with the maximum precision and speed.
Why we chose the Universitat Jaume I for validation
More than 90% of Spanish ceramic tile is produced in the Castellón Cluster, which is made up of 223 companies and is comprised of the geographical areas of Plana Alta, Plana Baixa and Alcala-ten concentrated in a 20-km radius. Central in this region is the University Institute of Ceramic Technology of the Universitat Jaume I. The Universitat Jaume I and the Spanish Society of Ceramics and Glass (SECV) together develop projects in the field of ceramic and glass materials. Jaume I University offers advice to organisations to implement innovation and technology solutions. With an open innovation model, the Universitat Jaume I collaborates closely with different organisations to promote instruments that carry out different parts of the process of knowledge and technology transfer in their field. It was therefore natural to choose this institute to perform an impartial research project within the area of their expertise of ceramics technology.