Glazes preparing

Name some chemical compounds used in a glaze preparation and explain why they are needed. 

When diboron trioxide is added to a glaze preparation having a slight amount of iron oxide, the resulting glaze may be milky or an opalescent blue. 

Apply each of the four glazes prepared to a separate fired clay slab. (Some of each glaze should be saved for a natural-clay pinch pot in Activity 4.7.) Cover beakers with watch glasses. 

Apply a glaze prepared in Activity 4.3 to the bisque ware. 

Seger s Porcelain. A German porcelain introduced in 1886 by H.A. Seger 30% feldspar, 35-40% quartz, 30-35% kaolin. It is covered with a glaze prepared from 83.5 parts feldspar, 26 parts kaolin, 35 parts whiting, 54 parts flint. It is biscuit fired at a low temperature and glost fired at Cone 9. 

Figure 1 Industrial size specimen of a low tension insulator Glaze preparation...

Color Matching. Color matching is a process in which a technician prepares a formulation, ie, a mixture of pigments in a desired medium, that has the color effects desired by the customer. A good color match in one medium, eg, plastic, is not always a good match in another medium, eg, ceramic glaze. Thus the medium as well as the processing conditions have to be identical to those used by the customer. 

Pharmaceutical Applications. Sucrose has a long history in the manufacture of pharmaceuticals. It imparts body to symps and medicinal hquids and masks unpleasant tastes. Sucrose also functions as a diluent to control dmg concentrations in medicines, as an ingredient binder for tablets, and to impart chewiness to the latter. Sustained-release medications and protective tablet glazes are prepared using sucrose (41). Sucrose-based sugar pastes are used to promote wound healing (58). 

Disodium Tetraborate Pentahydrate, Refined pentahydrate consumed in the Urhted States is used in insulation fiber glass, glass, fertilizers, and herbicides. Smaller amounts are used in antifreeze (see Antifreezes and deicing fluids), ceramic glazes, and cleaning agents. About 40% of the pentahydrate produced in the Urhted States is exported (101). A large-scale apphcation of this chemical is in the preparation of perborate bleaches. 

Polymethacrylates. Poly(methyl methacrylate) [9011-14-7] is a thermoplastic. Itis the acryUc resin most used in building products, frequendy as a blend or copolymer with other materials to improve its properties. The monomer is polymerized either by bulk or suspension processes. Eor glazing material, its greatest use, only the bulk process is used. Sheets are prepared either by casting between glass plates or by extmsion of pellets through a sHt die. This second method is less expensive and more commonly used. Peroxide or azo initiators are used for the polymerization (see Methacrylic polymers). 

Cadmium acetate is a colorant for glass and textiles, a glaze for ceramics where it produces iridescent effects, a starting material for preparation of the cadmium haUdes, and is an alternative to the cyanide bath for cadmium electroplating. In 1991, cadmium acetate dihydrate sold for 59.50/kg in 2 kg lots of reagent-grade material. 

Acryloid and Plexigum. These were soft gummy products of interest as surface coatings rather than as mouldable plastics materials. About 1930 R. Hill in England and W. Bauer in Germany independently prepared poly(methyl methacrylate) and found it to be a rigid, transparent polymer, potentially useful as an aircraft glazing material. ... 

The first methacrylic esters were prepared by dehydration of hydroxyisobutyric esters, prohibitively expensive starting points for commercial synthesis. In 1932 J. W. C. Crawford discovered a new route to the monomer using cheap and readily available chemicals—acetone, hydrocyanic acid, methanol and sulphuric acid— and it is his process which has been used, with minor modifications, throughout the world. Sheet poly(methyl methacrylate) became prominent during World War II for aircraft glazing, a use predicted by Hill in his early patents, and since then has found other applications in many fields. 

Problems of the preparation of a good doughnut glaze are similar to those encountered in icings. Doughnut glaze has a tendency to chip or crack and... 

Portions of a 20 g sample of the oxidant salt, prepared exactly as the published description [1], had been used uneventfully dining a few days. Subsequently, as a 2 g portion was tipped out onto glazed paper, it ignited and burned violently, leading also to ignition of the bottled material [2],... 

This oxide is used in making blue and green colored glass and in glazes for pottery, but in recent years the preparation of superconducting materials such as YBa2Cu307 has become a serious interest. Other materials containing mixed oxides have also been produced. 

Aguilar et al.54 prepared CBD ZnS and CuS to develop architectural glazing capable of withstanding hot tropical climates and windstorms. Lipowsky... 

Boric oxide is used to produce many types of glass including low-sodium, continuous filaments for glass-belted tires, and fiberglass plastics. It also is used to make ceramic coatings, porcelain enamels and glazes. Also, the compound is used as an acid catalyst in organic synthesis and to prepare several other boron compounds. 

The pure compound is used in glazes and enamels as an opacifying agent. It also is used to make colored glass, imparting yellow color to the glass. The crude form is used in flaming arc lamps. Another application of this compound is in the preparation of several other cerium salts. 

Lithium carbonate is used in enamels, specialty glasses and special ceramic wares. It is used to produce glazes on ceramics and porcelains. It also is used as an additive to molten aluminum fluoride electrolyte in Hall-Heroult process. It is the starting material to prepare many other hthium salts. The compound also is used in medicine as an antidepressant. 

Uranyl nitrate is used to prepare several uranium salts. Also it is used to make uranium glaze and decorative porcelain, and as an intensifier in photography. It is an analytical reagent (e.g., Redox titration). 

Preparation of Chromium. Perform the experiment in the presence of your instructor, in a fume cupboard Wear eye protection or a mask ) Roast chromium(III) oxide in an iron crucible. Triturate potassium dichromate crystals in a mortar, melt the powder in a porcelain crucible with the flame of a gas burner, pour the substance onto a glazed tile plate, and after it solidifies again triturate it into a powder. Weigh 12 g of roasted chromium(III) oxide, 12 g of the fused potassium dichromate, and 10 g of an aluminium powder, and thoroughly mix all the substances in a mortar. Spill 10 g of a calcium fluoride powder onto the bottom of a chamotte crucible, and then the prepared mixture. (If there is no chamotte crucible in your laboratory, make a box from asbestos paper in the form of a crucible and fasten it with wire.) Tamp the substance with a pestle and make a hollow in the middle using a test tube (see Fig. 120). 

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