There are huge number types of glass, different in chemical composition, method of production and application. The most common is sodium-calcium-silicate glass, which is used to make glass containers and dishes, sheet glass, many other types of glass products.
The composition of the blend (initial mixture) for the production of sodium - calcium - silicate glass products includes raw materials such as dolomite and limestone, which provide transparency, strength and the ability to form products at relatively low temperatures (about 1000oC).
GOST 23671-2020, Limestone for glass industry. Specifications, and nine standards for dolomite in the glass industry* will come into force in Russia in March 2021.
All documents were developed by the Institute of Glass to replace the standards of the Soviet era.
According to the new standards, dolomite and limestone are supplied in lump and grinder form. The deviation of mass fraction of calcium oxide (CaO) in different batches of dolomite should not exceed 0.75%, in different batches of limestone - 1%. In dolomite and limestone is not allowed to have impurities visible to the naked eye.
Chairman of TC 41 "Glass", Head of the Department of Standardization and Testing of JSC "Institute of Glass", Candidate of Technical Sciences, Alexander Chesnokov considered that the renewal of Soviet GOSTs for dolomite and limestone in the glass industry was necessary for several reasons:
Firstly, many documents are outdated or cancelled.
Secondly, since the introduction of the former GOSTs, the glass industry has stepped forward. Today, large factories in Russia use modern equipment. It is necessary to have a constant composition of raw materials for the stable operation.
In addition, the requirements for limestone and dolomite in the glass production on the chemical and particle size became harder for distribution over the past decades.
According to the old GOST of 1979, limestone was supplied to glass plants only in pieces that had to be crushed, ground, dried, etc. The new GOST includes several brands of ground limestone, which are fully ready to make a blend. The plant has only to dose the powder materials and send them to the kiln. It speeds up the technological process and improves the environmental situation at production.
The appearance of new methods for chemical composition control and modern equipment for their application also entailed corresponding changes in the 1979 documents on dolomite for the glass industry. Novelties have been introduced into the standard for general requirements of analysis methods. The standard has been supplemented by sections: "Terms and explanations", "Safety requirements", "Requirements for analysis conditions", "Quality control of results". X-ray fluorescence analysis has been introduced into the standards for methods of determining silicon dioxide, calcium and magnesium oxides, iron oxide and aluminum oxide. It allows faster and more efficient analysis of dolomite oxide content.
*Standards for dolomite, coming into force in March 2021:
GOST 23672-2020, Dolomite for glass industry. Specifications;
GOST 23673.0-2020, Dolomite for glass industry. General requirements for methods of analysis;
GOST 23673.1-2020, Dolomite for glass industry. Methods for determination of calcium and magnium oxide;
GOST 23673.2-2020, Dolomite for glass industry. Methods for determination of ferric oxide;
GOST 23673.3-2020, Dolomite for glass industry. Methods for determination of aluminum oxide;
GOST 23673.4-2020, Dolomite for the glass industry. Methods for determination of silicon dioxide;
GOST 23673.5-2020, Dolomite for glass industry. Moisture determination method;
GOST 23673.6-2020, Dolomite for glass industry. Method for determination of mass loss on ignition;
GOST 23673.7-2020, Dolomite for glass industry. Acid-insoluble residue analysis method.