Clay raw materials for production of mineral paints
Clay raw materials used for the production of mineral paints are powder and earthen versions of the oxide and hydroxide iron minerals containing the addition of the clayey minerals. There are several coloristic variants and their traditional names are: raddle – yellow or red, umbra – dark brown, terra di Siena – camel and ochre – gold-brown. These pigments are used for the production of oil paints, varnishes, enamels, putties etc. The production of natural pigments is of less importance nowadays, with the artificially produced pigments being used more often – they are characterized by the stable physical-chemical properties.
In Poland, only two deposits of ochre, clays and ochre claystones have been documented so far: Buk in Mazowieckie Voivodeship and Baczyna in Świętokrzyskie Voivodeship. In these deposits, in clayey sediments of Rhaetic–Liasseic, the ochre makes the lens accumulations.
In Baczyna deposit there are three types of ochre occurring, documented in a C1 category: yellow, red and brown. Nevertheless, this deposit has never been exploited. Buk deposit was exploited till 1976 and due to the resources depletion the production was abandoned. Nowadays, there are only anticipated sub-economic resources documented in the deposit (Table 1).
Due to the lack of the exploitation, the demand for the raw materials for production of mineral paints is fully covered by import. The Polish trade turnover of ochre are minor. In the last couple of years, the import of the natural pigments remained within the range of 800 – 1,000 tonnes per year with the import value of PLN 2.5 – 4.0 million.
Prepared by: Robert Bońda