Shading of colours in production of ceramic wares - reasons of formation

One of the most important problems we have to deal with in the ceramic whiteware production is maintaining the stable tonality of colour of the glazes and the decoration of the ceramic products. This difficulties are especially significant for the large batches of production like for example the ceramic titles. The manufacturing of the one assortment for a few days requires the multiple preparation of the glazes and decorative materials. Similar problems occur during the renewing of the production of the given assortment after a longer period of time. The presented paper shows the results of the research covering this topics carried on in The Department of The Ceramic Technology on the AGH Krakow Poland. It is presented the kinds of the factors that can influence the formation of the shadings of coloured glazes: way of mixing of the glaze with stains, time of the mixing and the firing curves. The obtained results of the colour differences ΔE00, calculated from the 'Cie L a b' measurements shows that the most important factor that influences the arising of the colour shading is the change of the firing condition and the sequence of the homogenization as the second important.