SOME NOTES ON THE COLOR OF ANTIMONY ENAMELS1

Pure white antimony oxide does not give as good a color or opacity in enamel as the gray, impure, domestic product. The better color and opacity of enamels made with the latter is probably due to the impurities contained in the antimony.     

SOME DATA ON THE COMPOSITION OF ARSENIC ENAMELS FOR COPPER1

Methods of application are by usual wet slushing, and sieving powdered enamel on to clean copper sheets and fusing to a smooth coat. Where slush-coat is necessary it is advisable to use an enamel free from lead and arsenic as a ground. In this work the dry method is used exclusively. In the formulae given, increase of SiO₂, increases fracturing or shivering, increase of B₂O₃ above 0.2 equiv. in presence of 0.1 equiv. AS₂O₃ causes enamels to come mat. Increasing KNaO at expense of PbO decreases opacity, improves fit and gloss, but makes enamel more soluble. The following limits in composition are recommended: 0.3 to 0.7 KNaO, 1.3 to 1.8 SiO₂, 0.7 to 3 PbO, 0.0 to 0.2 B₂O₃, 0.05 to 0.15 AS₂O₃.     

THE PRODUCTION OF SOME WHITE ENAMELS FOR COPPER1

The investigation deals with the development of some white enamels for copper watch dials, thermometer scale plates, and signs. The effect of varying Na₂O, PbO, cryolite, SiO₂ and B₂O₃ on the properties of the enamels was studied in twenty enamel compositions. The following conclusions were reached: (1) Correct melting is extremely important in the preparation of copper enamels; (a) Slow air cooling of the frit is preferable to quenching in water. (b) Repeated melting tends to promote opacity and to eliminate dissolved gases. (2) A somewhat reducing atmosphere during firing avoids oxidation of the copper. (3) Slight changes in enamel composition have a decided effect on the resultant properties. (4) Sodium oxide promotes gloss but reduces opacity very decidedly. (5) Lead oxide promotes fusibility without materially reducing opacity, except by dilution. (6) Cryolite is not a desirable flux or opacifier as it tends to develop a matt finish. (7) It is desirable to keep the boric oxide content low and good enamels may be produced without it. (8) By using “white arsenic” as an opacifier tin oxide is unnecessary. (9) The following were the best enamels obtained and these appear to be equal to a number of watch dial enamels examined: C-19 and C-20. 20. (10) A second group of compositions which appear to promote results equal to those in use for thermometer scales, advertising letters, etc., are C-10. 10. C-21, C-22, and C-24. In selecting these compositions, all factors such as opacity, gloss, texture, fit and resistance to attack of copper have been considered.     

SOME OBSERVATIONS ON THE DEHYDRATION AND FIRING BEHAVIOR OF CLAYS1

The results of laboratory studies of the drying and water-smoking behavior of twelve clays, typical of those used in the manufacture of clay structural units, are given and correlated with data obtained at plants during the firing of ware made from these same clays. There is evidently considerable difference in the time required to dry the materials investigated and it is indicated that the fire clays as a group are considerably more difficult to dry than are shales and surface clays. The results also indicate that the removal of hygroscopic and chemically combined water, as initially contained in the clay, are not important factors in regard to the time required to watersmoke and fire clay ware under plant conditions. With proper equipment it would appear to be possible to fire clay ware, approximating brick and paving block in size and shape, to 1832°F in 20 hours, but that the following conditions in practice may necessitate a longer firing time than that shown to be satisfactory in the laboratory: (1) the heating of ware which is not “bone dry” and which necessitates completion of the drying operation in the kiln; (2) the time required to complete oxidation; (3) the limitations necessitated by the kiln construction, the brick work of which may be destroyed by too rapid heating and cooling; (4) limitations of kiln design because of which enormous differences in temperature would develop throughout the setting by too rapid heating; and (5) insufficient movement of furnace gases to promptly remove all water vapor.     

THE EFFECT OF SOME SUBSTITUTES FOR TIN OXIDE ON THE OPACITY OF WHITE ENAMELS FOR SHEET STEEL1

The effect of replacements of tin oxide on opacity of enamels is always of interest. This investigation includes a study of some of the commercial substitutes for tin oxide in a standard frit as well as others which are not in common use. Zirconium oxide and sodium antimonate are apparently the best substitutes and rank very close to tin oxide. Next in order is zirconium silicate, although the purity of the material is of course very important. Opacity does not always increase with increase in amount of oparifier used. Proper calcination of opacifiers is of importance in their effect on opacity. Visual estimation is not an accurate method for determining the opacity of enamels, although it may be suitable for classifying enamels for such purposes as stove work and table tops. For accurate determination of reflecting value, the method employed by the Colorimetry Section of the Bureau of Standards is described. This involves the use of the spectrophotometer apparatus with illumination box as developed at the Bureau and the calculation of the total diffuse reflection from the spectrophotometric data.     

PROGRESS REPORT ON THE EFFECT OF FURNACE GASES ON THE QUALITY OF ENAMELS1

The appearance of sheet-steel enamels fired in atmopheres of nitrogen, carbon dioxide, sulphur dioxide, and Urbana city gas has been determined. A study of the effect of variations in the composition of sheet-steel ground coats and sheet-steel cover coats on their resistance to attack by sulphur gases has been made. Plans for future work on the problem are outlined.     

EFFECT OF SOLUBLE SALTS ON THE PROPERTIES OF ENAMELS1

Enamels, in common with other types of glasses, are more or less soluble in water, depending on their compositions. The nature and quantity of salts dissolved from the enamel glass during milling have a very definite bearing on the suspension, work ability, and other properties of the enamel, such as pitting and crawling. Those enamels which produce mill liquors which are excessively alkaline have very poor floating qualities. The ratio of free alkali to boric oxide dissolved from the enamel frit is an important factor in the flotation properties of the enamel. The poor floating powers of certain enamels can be corrected by the addition of suitable electrolytes. The kind and quantity of salts dissolved from the frit will determine the selection of the proper electrolyte. Enamel compositions having minimum solubility for good suspension and other properties are given. The value of an enamel clay cannot be determined by floating the clay in water. Tests must be made with the clay in the type of enamel with which it is to be used. Any studies on the effect of aging of enamels on their working properties must give consideration to the constitution and quantity of the individual salts dissolved from the enamel frit, and to the action of carbon dioxide in neutralizing part of the free alkali.     

EFFECTS OF COMPOSITION ON THE PROPERTIES OF SHEET STEEL ENAMELS1

The effects produced by the substitution of feldspar for flint and flint for feldspar together with variations in other constituents commonly used in enamels were studied with reference to their resistance to mechanical shock, thermal shock and acid attack. Tests were made on three series of enamels of twenty each which were applied to 8- inch steel dinner plates over a standard ground coat. The enamels of the series containing both flint and feldspar were found to be most satisfactory for general use. Results indicate that enamels having certain excellent properties, making them more suitable for special purposes, may be found in the other two series.     

SOME OBSERVATIONS IN THE CASTING OF HEAVY ELECTRICAL PORCELAINS1

A summary is given of experiences had in the manufacture of heavy and intricate electrical porcelains by the casting process. Some of the subjects discussed are selec- tion and test of clays, mixing of casting slip and its control, and several details of the methods used in casting the ware. Special emphasis is placed on the limits established for viscosity and specific gravity of the casting slip and the general proposition that the slip must be within the limits set for viscosity regardless of specific gravity.     

SOME OBSERVATIONS ON TERRA COTTA PHYSICS1

An apparatus for determining a representative “over-all” coefficient of thermal expansion of terra cotta under service conditions is described. Observations made show a decided contraction upon wetting the terra cotta and the temperature must be raised for the regaining of the original length. It is probable that the extent of mycelial capillaries is the determining factor of the magnitude of contraction. Further data obtained are presented and discussed.     

SOME RELATIONS OF COMPOSITION TO SOLUBILITY OF ENAMELS IN ACIDES1

Review of literature.—The literature on acid resisting enamels and glasses is reviewed. Acid resisting powers produced by different oxides.—When substituted one for another, in each case in equal percentage amounts, various oxides and minerals increased the resistance of various enamels to the action of boiling 20 per cent hydrochloric acid in the following order of effectiveness: Al₂O₃, cryolite, Na₂O, PbO, BaO, Li₂O, MgO, CaF₂, ZnO, SrO, CaO, B₂O₃. The first five mentioned were especially effective. The remainder are undesirable materials from the standpoint of acid resistance. Effect of the enamel base.—The relative effects of the materials were the same for various base enamel compositions. Effect of ZrO₂ and TiO₂. —ZrO₂ and TiO₂, when substituted for small amounts of SiO₂, increased the resistance of various enamels to attack by acids, ZrO₂ being most effective in this respect. The favorable action of ZrO₂, is offset by a tendency to produce excessive chipping. Rutile gives less chipping than either zirconia or silica and greater acid resistance than silica. Best compositions.—Enamels 2,17,19,26,27, and 33 of table 1 showed resistance to action of the acid equivalent to that of the original competitions based on the analysis of a French acid-resisting enamel. By use of the data developed in this investigation other highly acid-resisting compositions can readily be formulated.     

OBSERVATIONS ON THE FACTORY CONTROL OF FISH-SCALING1

An analysis of fish-scaling, its causes and prevention, based upon observations and experience of practical work. Three principal causes of fish-scaling are: (1) Improper firing, either underfiring or overfiring, especially the latter since its effects arc usually not evident until the ware is finished and marketed; (2) The use of a clay which does not give a free running uniform coat without the use of excessive amounts of flotation agents. Clays which, when stirred up with water give a persistent suspension are recommended. (3) Improper type of furnace for the firing operation. The author prefers the open type furnace for the firing of enameled ware.     

EFFECTS OF COMPOSITION ON THE PROPERTIES OF GROUND COAT ENAMELS FOR SHEET STEEL1

A series of ground coats was developed about each of three refractory bases, one of which consisted of flint and feldspar in a ratio frequently used commercially, another consisting of feldspar only, and the third of flint only. In each case the refractory portion was 58.5 parts of the whole. Besides the refractory, a “fixed addition” of 11.5 parts, comprised of 0.5 cobalt oxide, 1.0 manganese oxide, 5.0 boric oxide and 5.0 sodium oxide, was used in every enamel, bringing the basic constant portion for each series to 70 parts of the whole. The variable portion in each series was made up of equal parts of three constituents commonly used in enameling, chosen from a total of six in such a way that every possible combination was employed, making a total of twenty enamels in each series. All were given two cover coats of a standard white and tested for resistance to mechanical and thermal shock. In general the ingredients which were most conducive to resistance to the test treatments were flint in the refractory portion, and sodium oxide in the variable portion, constituted of fluxes. Also, boric oxide favorably influenced resistance to mechanical shock in the series containing both flint and feldspar. Resistance to mechanical and thermal shock in ground coats was considerably less affected by variations in expansivity than is the case in cover coats, the influence of that factor appearing to be partially obscured by other factors.     

OBSERVATIONS OF CAUSES FOR INCONSISTENT RESULTS IN COMMERCIAL FINENESS TESTS OF PORCELAIN ENAMELS1

Results are given of commercial tests showing inconsistencies in results obtained. Investigation proved these differences to be due to careless manipulation, clogging of screen openings in the original cloth as manufactured, and distortion of the mesh in fastening the cloth to the frame.     

EFFECT OF SODIUM ALUMINATE ON CONSISTENCY AND ACID RESISTANCE OF SOME ACID-RESISTANT ENAMELS*

This paper includes consistency studies and shows variations in acid resistance occurring with concentration and the method of using sodium aluminate as a setting-up agent.     

浅谈陈化对立德粉细度的影响

研究了陈化对立德粉细胞的影响,通过证验证明,缩短陈化时间有利于未煅烧立德粉中小晶粒（原级晶粒）的存在,达到较好的控制立德粉粒度的目的,结果表明,陈化在24h以内,可获得最佳的粒度为25μm,陈化时间越长,粒度越大。