NOTE ON THE HARDNESS OF GLAZES1

Method of measurement.—The apparatus used (figure 1) consisted of a hardened tungsten-steel point which was allowed to bear on the glaze surface for 3 min. under a pressure of 50 lbs. The hardness was then computed from the dimensions of the resulting indentation. Results were reproducible to about 5 per cent. (See table III.) The presence of ridges and bubbles in the glaze was the principal cause of discordant readings. Results and conclusions.—The enamels show the lowest and the porcelain glazes the greatest hardness, while the whiteware glazes occupy an intermediate position. The difference in hardness between the enamels and the whiteware glazes is quite marked. There is also a rather well defined difference between the whiteware and the porcelain glazes, but not a sharp separation between the lower and the higher fired porcelain glazes. Enough evidence has been accumulated to show that increased firing of the same glaze will increase the hardness. It appears also that increase in the alumina content brings about greater hardness.     

A GRAPHICAL REPRESENTATION OF THE MOLECULAR FORMULAS OF CERAMIC GLAZES1

A chart representing average glaze composition, including lead, fritted, Bristol, and porcelain glazes, as plotted against temperature is presented as a means for teaching glaze compositions and for getting a broad view of the constituents of glazes and their variation with temperature. The chart covers the range from cones 015 to 18.     

汝官瓷和钧官瓷的主成分鉴别

为了解多种釉色汝官瓷和钧官瓷的原料来源、成分和分类关系,正确鉴别两窑瓷器,选取汝官瓷样品34个、钧官瓷样品50个,由质子激发X射线荧光分析测定了样品的化学组分.将所有样品的7种主成分数据进行统计分析,得到以下分析结果:汝官瓷胎的Al2O3平均含量明显高于钧官瓷胎的,而CaO,TiO2的平均含量比钧官瓷胎的略高;汝官瓷胎的SiO2,Fe2O3,K2O平均含量明显低于钧官瓷胎的,而MnO平均含量比钧官瓷胎的稍低.汝官瓷釉的Al2O3,CaO平均含量明显高于钧官瓷釉的,而K2O,MnO的平均含量比钧官瓷釉的略高;汝官瓷釉的SiO2平均含量明显低于钧官瓷釉的,而TiO2,Fe2O3平均含量比钧官瓷釉的稍低,即汝官瓷釉和钧官瓷釉的主成分平均值是不相同的.模糊聚类分析表明:多数汝官瓷胎、钧官瓷胎样品的原料产地和成分接近但有所不同,汝官瓷釉和钧官瓷釉的原料产地和配方则明显不同.从主量化学组成上可以较好的区分汝官瓷釉和钧官瓷釉样品.     

PARTICLE-SIZE DISTRIBUTION OF GLAZES*

The particle-size distributions of experimental and commercial stains and glazes and glaze materials were determined by using the Andreasen pipette method. The variation in particle size of two porcelain glazes, raw and fritted, was correlated with the glaze working properties and certain physical properties of the glaze film, such as fluidity, microtexture, scratch-hardness, and glaze stress. The relation of grinding efficiency to length of milling time and different ball size was studied for these two glazes and also for a stain, and the color imparted by the stain at different grain sizes was noted.     

浅论陶瓷铜红釉色的自然美

陶瓷铜红釉是我国著名的色釉之一，以自身的特殊语言来表现其风彩神韵－－自然美，有自己的美学追求。它的自然美依赖于原材料，工艺流程，窑火及陶瓷艺术家的运用与创新。本文从工艺条件的作用，火的艺术，自然美的艺术表现形式三大主要因素及特点出发，通过大量的例证论述陶瓷铜红釉色的自然美。     

清凉寺窑汝瓷和张公巷窑青瓷釉的起源关系

为了探讨宝丰清凉寺窑汝瓷与汝州张公巷窑青瓷釉之间的关系,选取清凉寺窑汝官瓷釉样品31个,汝民瓷釉样品4个和张公巷窑青瓷釉样品32个,用中子活化分析(neutron activation analysis,NAA)测定每个样品中的24种元素的含量,并将NAA数据进行主成分分析及等级聚类分析.结果表明:常见着色元素Fe和Co汝官瓷釉的含量显著高于张公巷窑青瓷釉样品;汝官瓷釉料配方比较稳定,原料来源集中;汝民瓷釉料产地分散,且与汝官瓷釉料配方明显不同;张公巷窑青瓷釉料比较分散,但大部分样品与汝官瓷关系较近.由此,可以推断清凉寺窑与张公巷窑之间存在一定的联系.     

THE INFLUENCE OF CHEMICAL COMPOSITION ON THE PHYSICAL PROPERTIES OF GLAZES*

This paper presents some preliminary work on the study of the factors affecting fit of ceramic bodies and glazes. From the experimental work on 118 glazes and glasses, a method is outlined for calculating from the chemical composition of the glaze, approximate values of the tensile strength, Young's modulus of elasticity, and the mean linear coefficient of expansion of the glaze in the temperature range from 25°C to the lower limit of the critical range.     

The thermal and microstructural behavior of a R2O–RO–(ZnO)–Al2O3–(TiO2)–SiO2 based macro-crystalline raw glaze system

Macro-crystalline glazes containing significantly large crystals visible to the naked eye are a type of artistic glaze with a decorative and esthetic performance. The use of raw glaze compositions is a cost effective alternative for these types of crystal glazes. In the present study, R₂O–RO–(ZnO)–Al₂O₃–(TiO₂)–SiO₂-based raw glaze system was studied to produce macro-crystalline glazes for Limoges porcelain bodies. The influence of the addition of TiO₂ as a nucleating agent or major phase was evaluated in zinc-based glazes as well as ZnO-free ones. Designed glaze compositions were fired according to a special heat treatment cycle and characterized in terms of thermal and microstructural behavior using a digital microscope, differential thermal analyses, hot stage microscopy, X-ray diffraction, a scanning electron microscope, and energy-dispersive X-ray spectroscopy.     

A Ceramic Pigment Based on a By-Product of Nickel Production

A ceramic pigment that is a by-product of autoclave production of nickel is studied. Good technological properties and economic effectiveness of glazes containing this pigment are demonstrated. High-quality colored glaze coatings are obtained on porcelain and faience articles. The experimental results are confirmed by industrial tests.     

瓷釉化学成分之总观

本文论述三个问题：（一）各种常见瓷釉的基本化学特征；（二）瓷釉性质与网络离子和网络间离子平均场强之间的关系；（三）瓷釉中ＳｉＯ２：Ａｌ２Ｏ３变化范围之晶体化学论证。     

THE EFFECT OF DIFFERENT BODIES ON SOME WETTING AND FLOW CHARACTERISTICS OF GLAZES *

Variations in the fluid properties of glazes produced by different bodies were studied, and several methods for testing the wetting ability of the glazes were compared. An angle-of-contact method was found best for measuring the ability of glazes to wet bodies. It was found that different bodies had varying effects on the fluid properties of a glaze. The maturing temperatures of a glaze are not fixed for a given glaze but may vary as much as four cones on different bodies, if wetting ability is considered in determining this temperature.     

Firing process and colouring mechanism of black glaze and brown glaze porcelains from the Yuan and Ming dynasties from the Qingliang Temple kiln in Baofeng,Henan, China

Black glaze and brown glaze porcelains were an important part of ancient Chinese iron-based high temperature glazes. The excavation of black glaze and brown glaze porcelains from the Yuan and Ming dynasties at the Qingliang Temple kiln site in Baofeng, Henan, China, in 2014, enriched the firing history of this kiln site and history of Chinese ceramics. In this study, black glaze and brown glaze porcelain samples from the Qingliang Temple kiln site from the Yuan and Ming dynasties were selected and analysed via optical microscopy, laser Raman spectroscopy, focused ion beam scanning electron microscopy combined with EDS and energy dispersive X-ray fluorescence to determine their microscopic morphology, microzone composition, microstructure and chemical composition. Moreover, the main wavelength range of the brown glaze porcelain samples were measured by UV–Vis–NIR spectrophotometer systems. The main conclusions of this study are as follows. The brown glaze porcelain from the Yuan and Ming dynasties at the Qingliang Temple kiln site has two different colour layers, with the surface is brown and the bottom is black. The presence of a glass phase and α-Fe₂O₃ phase in the black glaze porcelain samples, and a rare ε-Fe₂O₃ phase in the brown glaze porcelain samples. The brown colour was a result of ε-Fe₂O₃ precipitation, whilst the black base layer also enhanced the brown-colouring effect. Different glaze formulations were used for brown glazed porcelain, some of which were similar to those used for black glaze porcelain and derived from the transformation of black glaze porcelain through different firing atmospheres and cooling rates. Although the formula of the brown glaze porcelain samples exhibited differences, the main wavelength difference was not large, was within the 645–682 nm range and belonged to the visible red region.     

Chemical and microstructural comparison of the export porcelain from five different kilns excavated from Nanhai I shipwreck

Nanhai I shipwreck, a fully loaded merchant ship of the Southern Song Dynasty, once heading for the Southeast Asia, represents the prosperous international ceramic trades during that time. Recent excavation provides us with the great opportunity to investigate the export porcelain on this ship. Black Porcelain and green porcelain of Cizao kiln, white porcelain of Dehua kiln, bluish white porcelain of Jingdezhen kiln, celadon of Longquan kiln, and white porcelain of Minqing Yi kiln were analyzed chemically and morphologically by polarizing microscopy, energy dispersive X-ray fluorescence spectroscopy and scanning electron microscopy with energy dispersive spectroscopy. The chemical and microstructural features of each kind of porcelain, evidently different from each other, are discussed in detail in this paper. Among them, the Dehua white porcelain and the Jingdezhen bluish white porcelain may represent the best manufacture techniques for their purest glazes and bodies. Also, anorthite crystals are common in the calcium glazes of the Longquan celadon and the Jingdezhen bluish white porcelain. The most interesting structure among the samples observed is the structure of crystals and MgFe rich phase separation in the black glaze of Cizao porcelain, which is also different from other black glazes studied in previous research.     

Potential fingerprints for the usage of botanic ash in the glaze recipes of the Jizhou tea bowl

A glaze slip made from a mixture of porcelain clay and flux was melted at high temperatures to form an amorphous glaze layer on a ceramic body. All information about the raw materials and recipes of the glaze was lost in this process, leading to difficulties in the reconstruction of the ceramic-making process performed in ancient China. Herein, the refiring experiment was performed and the thermal dilatometer (DIL), X-ray diffractometer (XRD), X-ray fluorescence (XRF) and field emission scanning electron microscope (SEM) were utilized to investigate the crystallization behavior in the glazes of an underfired Jizhou tea bowl. The results showed that diopside, fluorapatite, and anorthite crystallized from the heterogeneous glaze slip, induced by the inhomogeneity of the raw materials and the incomplete mixing process, during the firing process in the glazes of the Jizhou tea bowl. All these crystals melted with increasing temperature, indicating the importance of the underfired samples in reconstructing the ancient ceramic-making technique. Diopside and fluorapatite could be potential fingerprints to identify the usage of botanic ash in the glaze recipes.     

Raman identification of the different glazing technologies of Blue-and-White Ming porcelains

Shards of Blue-and-White Ming porcelain from shipwrecks of Portuguese ships found on the coasts of South Africa plus a shard from Mombasa (Kenya) were analyzed by optical microscopy, SEM-EDS and Raman microspectroscopy (458 nm). Whereas the Raman signature of porcelain body paste compositions which are based on mullite, quartz and an amorphous phase with the minor presence of anatase and feldspar are very comparable whatever the variable alumina content, at least two types of glazes are observed: a high-temperature soda-potassium glaze, and glazes richer in calcium and similar to a celadon glaze (with the possibility of wollastonite formation). The blue decoration is obtained with a material rich in manganese typical of the Ming productions. Some shards exhibit a two-layer glaze and the blue decoration is either placed under-glaze, or in-glaze as found in the Vietnamese productions of the same period. Previous assignments of the Raman signature of feldspar to cobalt aluminate are now not favoured (blue colour is obtained with Co²⁺ ions dissolved in the glassy silicate) and several black spots exhibit the characteristic spectrum of an epsilon Fe₂O₃ phase being present.     

Utilization of seashells in matte glaze preparation

In this study, the investigation of the optical properties and microstructural development of matte glaze compositions prepared with the addition of seashells was aimed. The seashells obtained from Black Sea beaches of Samsun, Turkey were characterized using XRF, XRD, FTIR, TG-DTA techniques, and heating microscope. The calcite-aragonite polymorphic transition was provided by heat treatment of seashell powders at 700°C for 1 hour and then, aragonite-based seashell powders were incorporated to matte glaze compositions up to 30 wt%. Firstly, four different types of fired body specimens (red clay, chamotte, white, and porcelain) were produced at 800ºC for 7 hour. Secondly, the prepared glazes were applied on surface of all fired bodies and then, all bodies were sintered at 1100ºC for 8 hour. Finally, coloring parameters and microstructural features of seashell added glazes were determined. The addition of seashells to glaze composition by 10 and 20 wt% resulted in higher transparency. The matte glaze was formed with increment of seashell content to 30 wt%. The more reduced fluidity of the glaze caused nonhomogenous matte appearance. As a result, it is possible to produce transparent glazes in eco-friendly and cost-effective way by addition of seashells into glaze composition in 20 wt%.     

Lead Free Cu-Containing Frit for Modern Metallic Glaze

A lead-free frit containing high amount of copper and its glaze conceived for fine porcelain stoneware tiles were investigated. The glazes obtained under industrial firing were studied using X-ray photoelectron spectroscopy, X-ray diffraction, optical and scanning electron microscopy with energy dispersion spectroscopy. The mechanism of the red color formation on the surface was explained. The results indicated that the glaze presents a metallic gloss and iridescent colors on the surface, mainly associated to the formation of CuO crystallites and Cu metallic particles. Moreover, the Cu glaze showed a good chemical durability; this is particularly interesting because commercial Cu frits usually present poor chemical properties.     

INFLUENCE OF GLAZE ON STRENGTH OF STEATITE TUBES AND NEW METHOD OF DETERMINING GLAZE STRESSES *

Different glazes have been applied on steatite tubes and the influence on impact and flexural strength has been investigated. Glazes applied on tubes with very thin walls affect the thermal expansion of the ceramic body. This fact has been used to test the glaze fit.     

Effect of alumina characteristics and concentration on thermal behavior,phase evolution,and aesthetic properties of tile glaze coatings

In tile manufacturing alumina acts as an opacifier in porcelain tile bodies and as a matting agent in glazes. Calcined alumina is a versatile and a new material for glaze industry due to it’s the densest and more stable crystalline form of alumina. The study was accented on examining of the effect of alumina characteristics and concentration on thermal behavior, phase evolution and optical properties of wall tile glazes. For this purpose several wall tile glazes which contain different phases of alumina and a different concentration were prepared and fired in industrial firing cycle. In the study it was showed that softening and melting temperatures of the wall tile glazes were increased with the increment of the alumina concentration. The crystal phases were detected as anorthite, corundum and gahnite. Depending on the forming of new crystalline phases, glazes with different aesthetic properties were obtained in the study.     

The white porcelains from Dehua kiln site of China: Part I. Chemical compositions and the evolution regularity

Dehua county in Fujian province of China has a long history of white porcelain production from the Song to Qing Dynasties. The development and flourish of Dehua porcelain has always been closely related to the export trade. In this part of the study, white porcelain samples of the Song to Qing Dynasties excavated from Wanpinglun, Qudougong, Zulonggong, Jiabeishan and Xingjiao kiln sites were analyzed to investigate chemical compositions of body and glaze and the evolution regularity in the course of time. The study demonstrates that the composition of Dehua body has similar evolution regularity through the Song to Qing Dynasties with Dehua glaze, and the samples of the Ming Dynasty have extraordinary high K₂O both in bodies and glazes.