ALUMINA IN WHITEWARE *

A brief résumé on an extensive investigation of the use of calcined alumina in white-ware bodies is presented. Its use in vitreous chinaware, semivitreous dinnerware, electrical porcelain, cooking ware, and sanitary ware is discussed. Data are given also on special alumina bodies of unusual strength.     

INVESTIGATION OF FELDSPAR AND ITS EFFECT IN POTTERY BODIES*

The history and purpose of the investigation are outlined and reports are made on (1) fineness determinations, chemical analyses, softening range, softening points, “true” specific gravity, thermal expansion, and petrographic analyses of the individual feldspars; (2) the results of porosity, volume shrinkage during firing, color and translucency, mechanical strength, petrographic analyses, effect of feldspar used on relative “glaze fit,” thermal expansion, and elasticity determinations on vitreous and semivitreous bodies in which feldspar is the only variable component.     

INFLUENCE OF FLUXES OF SPODUMENE AND FELDSPAR MIXTURES ON PROPERTIES OF CHINAWARE BODIES*

The most fusible spodumene-feldspar mixture used in these studies was composed of 30% of spodumene, 10% of potash feldspar, and 60% of soda feldspar. In semi-vitreous bodies and vitreous hotel chinaware bodies, however, the most effective fluxes were made up of 30 to 40% of spodumene, 40 to 60% of potash feldspar, and 10 to 20% of soda feldspar. Such fluxes lowered the maturing temperature of these bodies and improved their strength at lower temperatures. When they were fired at cones 6 to 9, their resistance to impact was equal to or higher than that of the feldspar bodies.     

THE SOLUBILITY OF QUARTZ AND CLAY IN FELDSPAR1

The literature on the subject is completely reviewed. The method used involved the addition of increasing amounts of kaolin to fixed amounts of feldspar and the addition of increasing amounts of quartz to fixed amounts of feldspar. All compositions were examined microscopically and the presence of undissolved kaolin was shown by the appearance of mullite needles, while the presence of undissolved quartz was shown by the presence of cristobalite. Soda feldspar is a better solvent for both quartz and clay than potash feldspar. The solution of quartz in soda feldspar starts at about 1350°C and increases with the temperature until at 1425°C. 32 parts of quartz per 100 of feldspar are dissolved. The solution of quartz in high potash feldspar does not start until 1400°C and only 4 parts are soluble at 1425°C to every 100 parts of feldspar. The solution of clay in soda feldspar starts at 1225°C and increases with the temperature until at 1425°C thirty-six parts are soluble. The solution of clay in high potash feldspar starts at 1250°C and at 1425°C the solubility is 20.5 parts per 100 of feldspar. The solution of quartz in porcelain bodies starts at the same temperature as it does in the pure feldspar which the body contains. The amount of solution per unit of feldspar is much greater. The general trend of one of the boundary lines in the ternary system K₂O-A1₂O₃-SiO₂ has been found.     

USE OF A HIGH SERICITE PYROPHYLLITE IN VITREOUS BODIES*

A pyrophyllite containing approximately 15% of sericite is being produced at Hemp, North Carolina. When it is substituted in vitreous bodies for all of the flint or all of the flint and some feldspar, a marked increase in fired strength results, and the shrinkage and absorption properties are not affected by this substitution. The types of bodies studied include electrical porcelain, made by the dry and plastic processes, sanitary ware, vitreous floor tile, and hotel china ware.     

EARTHENWARE BODIES AND GLAZES1

Effect of body composition on crazing .—-Six bodies of each of 2 standard clay compositions were prepared with variable clay and flint content and after biscuiting at cone 8 were glazed with 21 earthenware glazes and glost fired at cones 4 and 6. The results indicated that the variability of the silica content of clays would not be great enough to produce crazing in a well-balanced glaze. Effect of proportion and composition of frit .—-A standard whiteware glaze was compounded in 6 different ways and several other glazes in 2 ways. It was found that the method of compounding had no effect on crazing but it affected the gloss and fusibility. Increase in the percentage of material fritted increased the gloss and fusibility. With the same percentage of frit the best glost and highest fusibility were obtained when the flint and part of the clay were included in the frit. Effect of some variations in glaze composition .—-Substitution of CaO by Na₂O, pound for pound, as well as direct addition of Na₂O, increased crazing, improved gloss and increased the fusibility. Direct addition of feldspar increased crazing slightly and diminished gloss, but did not noticeably affect the fusibility. Substitution of 1½1/2 parts of feldspar for one part of flint to maintain the same fusibility increased crazing and diminished gloss. Direct addition of CaO improved gloss, increased fusibility and slightly reduced crazing.     

POTASH–SODA–LIME FELDSPAR EUTECTIC STUDY*

An investigation was made of the fusion behavior of the potash feldspar, soda feldspar, and soda-lime feldspar system, all materials being of commercial grade. The potash feldspar had a pyrometric cone equivalent of cone 9½, the soda feldspar, cone 6½, and the soda-lime feldspar deformed at cone 11½. Mixtures varying according to the triaxial diagram were made in the form of pyrometric cones. These were fired in groups along with standard Orton cones. The 30% commercial potash feldspar-70% commercial soda feldspar mixture reached 6 o'clock deformation when standard Orton cone 6 showed 2 o'clock deformation. The mixture of 62½% commercial potash feldspar with 37½% soda-lime feldspar reached 6 o'clock deformation when cone 7 showed 1 o'clock deformation, the deformation of the cone 9½ potash feldspar being reduced 3 cones by the addition of the proper percentage of the cone 11½ soda-lime feldspar. There was an increase in deformation temperatures (no indication of eutectic) in the plagioclase series, soda feldspar to soda-lime feldspar. The mixture of 30% commercial potash feldspar, 60% commercial soda feldspar, 10% soda-lime feldspar showed 6 o'clock deformation when cone 6 showed 1 o'clock deformation, this being the lowest temperature at which any member of the system showed 6 o'clock deformation.     

The relationship between the use of Zijin clay and glaze crackles for Chinese celadon with black body

The celadon with black body is a famous type of ceramic product in ancient China due to its appearance features, black body and crazing glaze, different from regular. For this type of ware, the crazing glaze is a kind of artificial decoration, not production defect. How the glaze crackles were made by ancient potter has always attracted many people's attention. And it has been studied mainly based on chemical composition. In this paper, we aim to provide our discussion and explanation for its sophisticated combinations of crazing glaze and black body. Based on analysis of ancient and modern celadon products, we thought that the difference in quartz content of the fired body is the reason why the celadon with black body is more likely to have crazing glaze than regular. And, the potter could control the expansion coefficient of the body by using Zijin clay with low quartz content as raw material.     

THERMAL AND MOISTURE EXPANSION OF KAOLINS AND BODIES FIRED TO DIFFERENT TEMPERATURES*

Thermal-expansion and moisture-expansion determinations were made on four kaolins of the Georgia, Florida, North Carolina, and English types alone and on typical semivitreous, hotel china, and electrical porcelain bodies embodying each of these kaolins after being fired at cones 6, 9, and 11. The Georgia and Florida kaolins and bodies showed surprisingly similar expansion characteristics. The general order of decreasing thermal expansion and increasing moisture expansion of the kaolins at all three firing treatments was Georgia, Florida, North Carolina, and English china. The semivitreous bodies at cones 6 and 9 showed the same order of expansion as the kaolins alone, but at cone 11 the thermal expansion of the English china clay body was the highest and the North Carolina kaolin body next in order. Moisture expansion of the bodies at cone 11 was found to be a function of the absorption, regardless of the kaolin used with no expansion obtaining at zero absorption. Mixtures of clay, flint, and feldspar, given an autoclave treatment after being fired to cones 6 and 9, showed that feldspar additions increased moisture expansion. When these mixtures were dehydrated at different temperatures, the data obtained were insufficient to confirm any theory on the nature of moisture expansion in a porous ceramic body.     

METHOD OF MEASURING STRAINS BETWEEN GLAZES AND CERAMIC BODIES1

A new test was developed for comparing the strains existing between different glazes or other ceramic finishes and the bodies to which they are applied. By its use these strains may be so adjusted that the finishes will be in suflicient compression to prevent crazing from subsequent expansion of the body without causing initial shivering. The new test is particularly valuable because the measuremen & are made on combinations of glaze and body prepared and treated almost exactly like those intended for regular use and because of the simplicity and cheapness of the apparatus required. A modification of the test provides a comparison of the moisture expansions of different bodies.     

MOISTURE EXPANSION OF GLAZES AND OTHER CERAMIC FINISHES1

Research for ascertaining why some glazes are more resistant to “moisture crazing” than others revealed the fact that certain glazes expand, because of the action of water, similarly to some of the ceramic bodies t o which they are applied. Although a control of this type of expansion is very important in fitting glazes to bodies, it has not been previously considered. Its importance should be evident at once when it is considered that a large “moisture expansion” in a glaze or other finish is in many cases an indication that the glaze will not be so liable to craze when the ceramic ware or material on which it is used is exposed to moisture. This follows since the glaze and the body on which it goes and which is ordinarily very susceptible to this kind of expansion will then increase in size simultaneously and more nearly at the same rate. Such conditions lessen the tendency of the body expansion to cause tensile stresses in the glaze. In this investigation specimens of various finishes were subjected to steam at 150 pounds per square inch for an hour because it was known that this treatment of such materials produces effects similar to those caused by long exposure to weather. This artificial weathering treatment caused in lustrous glazes an average expansion of 0.004%, in mat glazes 0.011%, in vitreous slip finishes 0.005%, and in porous slip finishes 0.033%. The moisture expansion of one of the mat glazes was 30% of the average obtained for a ceramic body having an absorption of approximately 12%. This proclivity of ceramic finishes to expand by the absorption of moisture can be controlled in their manufacture.     

THE CONTROL OF GLAZE-FIT BY MEANS OF TENSILE TEST SPECIMENS1

The selection of a suitable glaze for a particular body by usual inspection of a field of glaze trials is not sufficiently precise, and gives no indication of slow crazing tendencies. A new method of selecting glazes depends on the effect of a glaze on the strength of a porcelain tensile test specimen. The best fitting glazes increase the strength while poorer ones decrease it. Glazes which craze weaken the specimens very markedly. Results obtained with various glazes on one fire porcelain are given.     

THE EFFECT OF GLAZE COMPOSITION ON THE CRAZING OF TERRA COTTA1

Comparing the effects of equal molecular additions of the various components of the glazes in this study, it was found that ZnO and feldspar overcome crazing, ZnO being the more effective. MgO, BaO and CaO tend to produce crazing, MgO having the greatest tendency and the effect of BaO being somewhat greater than that of CaO. SnO₂ has no effect on the crazing. Increase of clay is more effective in overcoming crazing than any other changes that can be made in the glaze formula. Addition of small amounts of clay are more effective in overcoming crazing than much larger additions or substitutions of the other components. Increase of flint (per molecular equivalent) is less effective in overcoming crazing than increase of either clay, ZnO or feldspar, although, generally, considerable more flint than clay or ZnO can be added without appreciably changing the maturing point of the glaze. In many cases, increase of flint will not overcome crazing in a glaze.     

高温钛乳浊生料釉的研究

本文对钛釉用于卫生瓷生产进行了研究．讨论了ＴｉＯ２外加量以及长石，石灰石含量对釉面色泽，白度的影响．利用Ｘ射线衍射和偏光显微镜，对析出晶相的种类和分布进行了分析，在此基础上对钛釉的乳浊机理进行了探讨．     

USE OF DOLOMITE AS AN AUXILIARY FLUX IN FLOOR TILE*

It is a recognized fact that dolomite is a valuable addition as an auxiliary flux in white ware bodies, and an excellent glaze ingredient providing another RO member which imparts low thermal expansion to the glaze. There is evidence that the addition of dolomite to sanitary-ware bodies has resulted in the lowering of the firing temperature without daunting or other ill effects. The present investigation involved a study of the use of dolomite in floor-tile bodies. A review of the literature showed that little or no work has been done in this field, and it was, therefore, necessary to follow somewhat closely investigations carried on in the vitreous sanitary ware and dinnerware fields to determine the optimum percentages of dolomite to be incorporated in the test batches. A typical floor-tile composition was taken as standard and dolomite was substituted in increasing amounts at the expense of the accepted flux. The purpose of this investigation is to ascertain if economies could be effected in lowering the firing temperature of the body by the addition of small amounts of a less costly constituent.     

STUDY OF GLAZE PENETRATION AND ITS EFFECT ON GLAZE FIT: I-III*

A method for determining glaze penetration was developed and the effect of glaze penetration on glaze fit studied. The effects of twenty-four fluxes on penetration of a base glaze into semivitreous, hotel china, terra cotta, cordierite, pyrophyllite, wall tile, and steatite bodies were determined. The result shows that glaze penetration affects glaze fit and that penetration varies greatly, depending on glaze composition and the character of the body.     

CERAMIC ABSTRACTS

Glazed specimens of a commercial semivitreous body were fired according to a production tunnel-kiln schedule, and draw trials were taken out and quenched at frequent temperature intervals. Thin sections of these specimens were examined with a petrographic microscope for a determination of the constituents in the glaze and at the interface. The volume of the bubbles, undissolved feldspar, and undissolved quartz were measured for each temperature.     

OVERGLAZE POLYCHROME CONE NO. 61

The colors and glaze described enable the operator to paint figures, landscapes, or any decorations desired over an unfired glaze sprayed over a flat surface. Not having the ornament modeled in bas-relief, the ware can be fired with the regular terra cotta to cone 6. The body glaze can be sprayed over a terra cotta body having 35% calcined grit added. If a more sandy body is used, less silica should be added to the glaze to counter-act crazing.     

THE MELTING RELATIONS OF POTASH FELDSPAR,SODA FELDSPAR,AND FLINT MIXTURES1

P.C.E. values of ternary mixtures of potash feldspar, soda feldspar, and flint were determined and results shown on a solid phase diagram. No eutectics were developed with either of the binary series of feldspar and flint. The soda feldspar-flint mixtures were more refractory than were those of the potash feldspar series. At least 20% flint variation with potash feldspar will show no change in P.C.E. values and at least 10% with the soda feldspar showing the unreliability of P.C.E. to indicate the amount of the quartz content.     

自然流纹艺术釉的研制

利用德化陶瓷工业常用原料,采用正交与单因素实验,系统研究了釉料配方中黑泥、瓷石、长石、锆英粉的量以及釉层厚度、保温时间、烧成温度、干燥方法等因素对釉面流纹效果的影响,确定了最佳釉料配方及工艺参数.实验结果表明:釉料组成是影响流纹釉效果的内在因素.当面釉中黑泥加入量为8％时,可使釉面在干燥时开裂;瓷石加入量为61％时,会...