Clay Slips Research Articles

Method for the characterization of electrophoretic properties of clay slips

The present study presents experiments performed in an aqueous dispersion of clays and clay minerals using three different instruments, which were prepared to measure electric conductance, relative viscosity, and electrophoretic mobility of slip in flow. Smectite–kaolinite and Cloisite Na+ were used, in addition to an aqueous solution of sodium silicate in deionized water. Laboratory tests of zeta potential and viscosity were also carried out. The starting point was the natural behavior of the electric current when sodium silicate was added to the aqueous dispersion of clay or clay minerals. The results were analyzed and correlated considering the electrophoretic phenomenon. The method proved to be effective for understanding electrophoretic properties acting on the dispersion slips.

Deflocculant consumption of clay suspensions as a function of specific surface area and cation exchange capacity

AbstractCeramic tile production by the wet route requires clay suspensions with a high solid content and low viscosity. In this work the deflocculation of clays in aqueous suspensions was investigated by varying the type of clay and additive. Three kaolinitic and two illitic clays were characterized and dispersed with deflocculants based on lithium, sodium and potassium silicates and polyacrylates. The clays were characterized by chemical and mineralogical analyses, particle size distribution, zeta potential, organic carbon content, cation exchange capacity (CEC) and specific surface area (BET). Deflocculation curves were determined by measuring the viscosity for 50 wt.% clay slips. The results indicate that additive consumption is closely related to CEC and BET, which correspond respectively to the chemical and physical characteristics of the clay mineral's surface. Moreover, viscosity values at the deflocculation point are closely related to BET.

Investigation of Neolithic ceramic pigments using synchrotron radiation X-ray diffraction

Crystalline phases present in pigments scratched off the surfaces of some decorated ceramic sherds belonging to the Cucuteni Neolithic culture were successfully identified using synchrotron radiation X-ray diffraction at Daresbury Laboratory. The ceramic sherds were selected from a collection of the National Museum of Romanian History in Bucharest. The synchrotron radiation X-ray diffraction analysis revealed that the black-color pigments on the surface of a number of sherds were produced by a variety of jacobsite (Fe2MnO4) phases; magnetite (Fe3O4) was also found in one of the sherds. The red color was derived from clay slips with a high content of hematite (Fe2O3). Calcite (CaCO3) was found in the white pigments; its presence was explained as being related to postburial deposition processes. Conclusions on technological aspects, provenance, and conservation issues are given.

Estudo do comportamento reológico de barbotinas preparadas com argilas da Formação Corumbataí utilizadas no pólo cerâmico de Santa Gertrudes (SP)

Este estudo surgiu da necessidade das indústrias cerâmicas do pólo de Santa Gertrudes (SP) se adaptarem às mudanças do comportamento do mercado e às exigências dos órgãos ambientais em relação aos riscos causados pela geração de poeira na fase de preparação da massa. Assim, o processo de preparação de massa via úmida pode ser uma alternativa para esta substituição, sendo necessária a obtenção de uma barbotina que apresente um comportamento reológico adequado ao processo e ao consumo de energia. Foram feitas medidas de viscosidade, tensão de cisalhamento e taxa de cisalhamento com viscosímetro rotacional, tendo como parâmetros de controle, o teor de sólidos da barbotina e a granulometria. Desta forma, foram verificadas variações das suspensões, como o comportamento pseudoplástico e a tixotropia. Também foi analisada a dependência do comportamento reológico com a mineralogia das argilas, obtida por difração de raios X. Os resultados das curvas reológicas mostraram-se muito coerentes com a mineralogia determinada, indicando uma piora do comportamento reológico no sentido da base para o topo da Formação Corumbataí, devido à alteração supérgena e presença de esmectitas.

Deflocculating Effect of Sodium Polymethacrylates on Aqueous Clay Suspensions

The ability of sodium polymethacrylates salts with various molecular weights (1200 to 30000) to deflocculate concentrated aqueous suspensions (56 wt%) of two Indian ball clays was investigated. The ball clays were one from Bikaner, Rajasthan and the other from Bhimandole, Andhra Pradesh, which are widely used in Indian sanitaryware and tile industry. The clays were characterized for their chemical analysis, cation exchange capacity (methylene blue index test) and for particle size distribution. The clay slips were prepared with distilled water and water containing calcium ions (0 to 60 ppm) using sodium polymethacrylates as deflocculant. All the slurries showed non-Newtonian behaviour. Polymethacrylates with low molecular weights (1200 to 2500) were found to be the most efficient deflocculants for these clay suspensions. The salts acted by an essentially electrosteric stabilization mechanism in combination with a high sequestering ability towards flocculating cations (calcium ion binding power values of 760 to 790 mgCaCO3.g−1). For their efficient deflocculating capabilities towards concentrated clay suspensions, sodium polymethacrylates may be considered for practical industrial application, in particular, for the preparation of liquid deflocculants.

Characterization and study of sorptive properties of differently prepared organoclays from a brazilian natural bentonite.

Organoclays are used in cleaning natural waters from dissolved hydrocarbons by secondary sorption. Aiming future applications in this field, a Brazilian polycationic bentonite was used to prepare HDTMA organoclays, by using different quaternary ammonium salt loadings and clay content slips, to evaluate how these conditions may affect their sorption properties. The organoclays were characterized by CHN analysis, X-ray diffraction, thermogravimetry, and differential thermal analysis. For secondary sorption tests, to compare with published studies, toluene was used as a reference sorbate. Characterization and sorption results indicate that the Brazilian bentonite organoclays prepared in this study have a potential industrial use in environmental applications.

The techniques of painted Attic pottery

PREFACEOVER FORTY YEARS have elapsed since the publication of the book ThenCraft of Athenian Pottery by Gisela M. A. Richter in 1923, and, although it has beennlong out of print, the book continues to be useful. Most of the content of the booknremains valid today, and I gratefully acknowledge the standards and guidance MissnRichter established. In particular, many of the references to ancient literature whichnI use are based on her comprehensive chapter on the subject. Before writing her book.nMiss Richter engaged in the actual practice of making pottery and experienced thendifficulties of throwing, turning, and firing vases. She felt that to fully understand thentechniques of the craft, it was necessary to master them; this is still an essentialnapproach.The techniques used to produce Attic pottery have long intrigued scholars, butnonly in the past two and a half decades has important progress been made in analyzingnand reproducing them. The turning point in the technical study was the reproductionnof the ancient black glaze in 1942 by Dr. Theodor Schumann.There remains ample material for further study in the techniques of Attic pottery.nFirst, in the field of the pottery techniques used to form the vases. Second, in the field of the accessory colors or colored clay slips. Third, in the technical analysis of the black glaze. Fourth, in the discovery of the means by which the Greek painters applied their black glaze and accessory colors to the vases, including the proper sequence of this process. Fifth, in the reproduction of the technique of making the celebrated Attic relief line, which, though studied, had never been successfully reproduced.This study is mainly concerned with the techniques of Attic pottery of the black- figured and the red-figured styles, the period from the late seventh to the late fourth century b.c. It is the era which constitutes the high point in the exercise of Attic ceramic skill and attainment. In addition, however, I have included some studies of other periods and cultures, from the Egyptian black and red ware of the third millennium b.c. to the Barbotine pottery of the Roman period as late as the fourth century A.D., wherever they have bearing on the techniques of Attic painted pottery. I have made no attempt to be comprehensive other than in the selected time, although in it a broad span of pottery techniques can be studied.n n n n

Archaeometry of medieval Islamic glazed ceramics from North Yemen

Microscopic examination and electron microprobe analysis were employed to determine the materials and techniques used to decorate ten glazed types of medieval Islamic ceramics from North Yemen. Eight types were underglaze-painted, one was slip-painted, and one was monochrome glazed. The glazes were of two compositions, soda–silica and lead oxide – silica with annealing temperatures of approximately 835 and 640 °C, respectively. The colourants used in the glazes and paints were cobalt (blue), iron (green), copper (green and blue), and antimony (yellow). Where clay slips or slip-paints were present, alumina enrichment of the glaze had occurred during application or firing, and pigment-paints on top of slip grounds masked enrichment. The Mellor ratio for the lead glazes ranges from 0.68 to 0.74 and is well above the acceptable safety limit of 0.5.

Rheological and casting properties of two Egyptian clays

Slips from Kalabsha and Malkatta clays, widely used in the Egyptian ceramics industry, were prepared with the aid of an appropriate deflocculant at a constant specific gravity of 1·80—which lies within the practical working range for the slip casting technique. The rheological and casting properties, including plasticity of clay pastes, apparent viscosity and thixotropy of the clay slips, as well as casting rate, water retention, porosity and mechanical strength of their casts, were studied. The two clays behave in a quite different manner, reflecting the marked variation in their nature. Kalabsha clay slip has the minimum apparent viscosity with moderate thixotropy in the presence of 0·8% deflocculant addition, while Malkatta clay slip needs twice as much deflocculant to attain maximum fluidity, which is accompanied by a little higher thixotropic structure. Kalabsha clay slip casts faster and leads to cast having lower water retention, shrinkage, modulus of rupture and bulk density and of higher apparent porosity than that of Malkatta slip. In formulating ceramic bodies processed by the slip casting method, a blend of the two clays must be utilized in order to get a mixture having the proper flow properties and the best casting qualities. For thin-walled articles, the content of Kalabsha clay should be kept lower than that of Malkatta clay; the reverse holds for heavy-section casts.

Manganese black as an Etruscan pigment

Scientific examinations of a number of black decorations on Etruscan terracottas have shown the presence of a manganese iron paint slip (manganese black). The blackcolour is mainlydue to the presenceof the spinel jacobsite (MnFe2O4). This pigment is formed by firing under oxidizingconditions manganese- and iron-rich clay slips. The manganese black technique therefore differs significantlyfrom the classiciron-reduction technique. Its main advantage is that red and black colours can be obtained in one oxidizing firing-cycle. The manganese black technique was first used in the Near East and the Balkans (seventh to first millenium). This contribution reports its occurrence for the first time in the Etruscan area.

More Black Slip Vases from Central Gaul with Applied and Moulded Decoration in Britain

SummaryThe method of manufacture and application of plaques is discussed, also the use and length of life of moulds, in modern ceramic factories; together with the results of experiments in laboratories on the colour and content of clay slips. In Parts I and II respectively are described and illustrated thirty plaques and twelve moulded beakers.The (lost) Oundle Form 64 by LIBERTVS in red samian is discussed; and there are further comments on the black ‘cup’ from Colchester mentioned in the 1957 paper.

Continuous filterpressing of clay slips

Continuous filterpressing of clay slips

New type of mills for preparing clay slips

New type of mills for preparing clay slips

泥しょう鋳込成形の流動学的解釈

泥しょう鋳込成形の流動学的解釈

粘土懸濁液の揺変性の測定

粘土懸濁液の揺変性の測定

Effect of Initial Drying on the Casting Behaviors of Some Industrial Clay Slips

The effect of the initial drying of some industrial clay slips on the casting behavior was investigated in connection with the phenomenon of cationic fixation in clay minerals, which has been reported in this journal by one of the authors.Some industrial slips (Table 1) were dried at the temperatures below 300°C, and again were added with the equal amount of water as before. The rate of increase of the thickness of cast wall was estimated by measuring the change of the head of slip during the casting operation. The drying shrinkage, strength, porosity, and bulk density of the greens were also measured.It was confirmed that the pretreatment of drying introduces some marked changes in casting properties as well as in the physical properties of greens, although the effects seem too complicated for arriving at some simple conclusions.The present data, however, suggest that the history with respect to the drying of the mix governs the casting behavior of slips. This is important when scrap is recovered to prepare casting slips. At the same time, the authors pointed out that there is the possibility for improving the casting behavior of some special slips through drying treatment.

The Rheology of Clay Slips

Abstract A method of measuring the particle size distribution in clays using photo-sedimentation is first described and the importance of such knowledge for the understanding of the flow properties of clay slips is illustrated. Measurements of the velocity distribution of such suspensions contained in the annulus between concentric cylinders are used to show how the viscosity varies with the rate of shear. Finally measurements of the attenuation of an ultrasonic beam in sediments of different mean particle size are reported.

泥しょう鋳込の流動学的考察

泥しょう鋳込の流動学的考察

Some Influences of the Fixation Phenomenon upon the Rheological Properties of Clay Slips and Plastic Masses

It was first unveiled by the author that the binding power of adsorbed cations to the surface of clay minerals is increased by drying; and it was named as “fixation phenomenon.” As this is accompanied by the change of zeta potential of the clay surface suspended in water it would be very convincing that the fixation brings out some important change in the clay-water system.The present paper contains the results of the investigations on the influences of drying of Kaolinitic ceramic materials upon the various rheological and physico-chemical properties of slips and plastic masses. The results were interpreted from the view point of the fixation phenomenon as there is no room for doubt that it is one of the highly important factor governing the nature of clay-water system on drying.It was confirmed that the drying of kaolin minerals in the form of slips and plastic masses gives a considerable change in physical and chemical behaviors even if they were dried at the temperatures as low as below 50°C, which suggests the importance of the “drying history” not only in the studies of colloid-chemical or rheological properties but also in industrial process control. Furthermore, the possibility of the improvement of casting properties of a certain special slips through drying was pointed out.

The Effect of the Kind of Clay Raw Materials on the Physical Properties of the Quality of Pot used for Optical Glass Melting

As a continuation of the author's previous papers on “The Effect of Grain Size Distribution” and “The Effect of Chamotte Content” on the Physical Properties of Pot Materials used for Optical Glass Melting, the effect of eight kinds of clay raw material covering kibushi-clay, gairome-clay, koalin and roseki-clay as well as the effect of their mixing ratio on the physical properties were studied for seventy-one different pot materials in which the grain size distribution and the content of the chamotte were kept constant.After measuring the chemical composition, the distribution of grain size, and the buffering action of clays used, the content of water glass, used as the dispersing agent, was determined so as to make the slip to have constant fluidity while keeping the water content of the slip as small as posible. In the measurement both the method of determining the limiting water content for flow, and that of measuring the time of flow of the slip by funnel were employed, and by these determinations following facts were clasified: (1) Kaolin and roseki-clay can be dispersed in the water glass of the quantity 1/2 to 1/10 of kibushi-or gairome-clay. (2) The fluidity becomes low, for any kind of the clay used, when a part of the water-glass is replaced by soda containing the same quantity of Na2O. (3) In mixed clay materials the highest fluidity is obtained when the water-glass content is equal to that culculated additively from the content of water-glass to give the highest fluidity for each component clay. (4) For dried or burned clay samples cast from clay slips having equal water content and different water glass content, those cast from slips containing water-glasses of highest fluidity are not densest. It was formd that the drying properties of pot materials, cast in the way mentioned above, did not change remarkably by the replacement of kibushi by gairome-clays and vice versa. They showed, however, remarkable change by the substitution by kaolins. Hence, the use of kaolin is limited and it must be used with care, while roseki-clay may be used much more easily in the range of the content below 20 per cent.For pot materials burned for 2 hours at 1500°C, although the burning shrinkage and the apparent density changed additively with the addition of clay, the denseness, represented by apparent density and porosity, showed the tendency to become dense by the addition of clay raw materials, except for two kinds of gairome-clay used. Althou gh kaolin increased the burning shrinkage and the apparent density of pot materials, the degree of increase is less compared with the effect on their drying properties, and roseki-clay made pot materials to have low firing shrinkage and to be dense.The strength of burned pot materials are generally increased by the addition of clay, especially when Korean-Koalin was mixed with respective kibushi-or gairome-clay, pot materials became extremely strong at about 30 per cent of Korean-Kaolin content, and roseki-clay also made then strong in the range up to 20 per cent, of its content. Although the strength of pot materials quenched at temperatures when the pot is pulled out of the furnace after the glass is melted or when the glass batch is thrown into the pot was not so much changed as the case when they are showly cooled. They were stronger when they had larger content of kibushi-or gairome-clay and they were weak when they had large content of koalin. The spalling resistance expressed by the ratio of the strength of quenched to that of slowly cooled materials, showed the general tendency that the larger the strength of slowly cooled materials, the smaller the spalling resistance, although dense materials were not always weak in spalling and materials having 12-16 percent porosity were relatively strong.