CHAPTER 18

Tiles and Pottery with Color Magnesite Cement Work

MAGNESITE CEMENT WORK is a mixture medium producing a hard marble-like quality and does not contain any Portland cement, but is given in this book in order to complete the possible plastic mediums for the worker wishing to mold objects with permanent durable mediums.

MAGNESITE CEMENT IS A SUCCESSFUL INDUSTRIAL MATERIAL and is used by builders in interior trimmings for floor tiles, in making of bath-room surfaces and recently used in coating stairways and hallways, producing a pleasing texture and durable surface. The material is fireproof, cleanly and better than marble.

MAGNESITE IS A FORM OF LIMESTONE and is a carbonate of magnesia which is produced by burning until all gases have been eliminated, leaving only the oxide in the form of a pure white powder. It comes from Europe and is found in Maryland, Massachusetts, New York, Vermont, California, and Washington. It has been used extensively in Europe and when better known will be used more generally in America.

MAGNESITE CEMENT AS AN ENAMEL has been used as a hardening surface on concrete and cement surfaces and also on clay brick. The concrete or cement or brick surfaces should be thoroughly moistened before the magnesite mixture is placed upon it to avoid the moisture from the magnesite being absorbed and improperly drying.

THE MATERIALS FOR PRODUCING MAGNESITE are calcined powdered magnesite, chloride of magnesia, sulphate of magnesia, white sand, white talc and fine sawdust.

The magnesite should be kept in a container, proof against exposure to air and dampness, in order to preserve its full setting qualities.

Chloride of magnesia has the appearance of ice or alum and when exposed has the tendency to dissolve but does not deteriorate. It is the chemical which when united with the magnesite produces the binding or cement qualities.

Sulphate of magnesia or epsom salts is an easily secured material and is used in very small quantities in the formulae for producing magnesite cement and which is given later in this chapter.

The white talc or soapstone used for giving a smooth and polished white background is used as a filler.

White sand and the fine sawdust should be absolutely clean and are mixed with the other ingredients to produce the composite mixture to produce Magnesite Cement.

TO COMBINE THE INGREDIENTS proceed as follows:

FIRST MIXTURE. Two and one-half pounds of powdered magnesite and one pound of white talc are mixed thoroughly with one quart of fine sawdust. To this mineral, dry color similar to that used and described for color cement should be added if a color tone is desired. About one-half as much color should be used as there is magnesite. In other words, one pound of color should be used with two and a half pounds of powdered magnesite. A stone mortar should be used to grind the entire mixture well together.

This first combination is a dry mixture and is then mixed with the second mixture which is liquid.

SECOND MIXTURE. Take five parts by weight of chloride of magnesia solution with a density of 25 tested with a Baumé hydrometer which is a simple glass tube secured at any druggist for registering solutions. To the chloride of magnesia solution add one-half part by weight of sulphate of magnesia which is epsom salts and test with the hydrometer until it records 15.

TO USE THE HYDROMETER, place water in a container and if the hydrometer is placed in it, it will register “0” and when the chloride is placed in it, and dissolves the hydrometer will commence registering the density of the solution. When it records 25 no more chemical should be added. More water should be added to correct the density if needed. The same procedure is followed for registering the 15 for the epsom salts.

Chloride of magnesia will dissolve more rapidly if it is broken up, and distilled water may be used if the usual available water contains lime, iron or other injurious minerals. Some workers use rain water for many purposes.

THE FINAL MIXTURE, or third step in the mixing, is to take the first dry mixture and add enough of the second liquid combination to produce a thick creamy mixture of the two. Strain this after it has been well mixed.

TO PRODUCE TILES OR OTHER OBJECTS, THE MATERIAL is quickly poured into the molds. A brush may be used for brushing the material well into the edges and corners. A gentle jarring of the mold will remove the air bubbles and the molds with the magnesite is permitted to dry for seven to ten hours before the cast is removed from the mold.

FOR VARIOUS COLORS in the same design, the dry mixture can be mixed with color and the liquid, or second mixture, added to it. This can be applied to the mold in the same way as the color was used with cement, and after it has set, can be backed with a general color of magnesite cement or with plain magnesite mixture.

TO FINISH MAGNESITE let it remain drying for two or three days after which it can be washed with slightly warmed water to remove the thin scum on the surface. A thin coating of beeswax or floor wax well polished will finish the article.