Recrystallization of Cerium Oxide in Porcelain Enamels

The effect of cerium oxide incorporated as the principal opacifying agent in the frit batch on the properties of white cover-coat porcelain enamels was studied. The effect of several variables on the opacity of the enamel was investigated as a function of firing temperature. Variables studied included (a) the amount of cerium oxide added, (b) the manner in which cerium oxide was incorporated into the enamel, i.e., mill addition, frit addition, or combination of both, (c) composition of the base glass, (d) weight of application, and (e) type of mill addition. Porcelain enamels were produced which had good acid resistance, high gloss, and a reflectance of 80% or more. Mill-added cerium oxide seemed to be less effective than that which was incorporated in the porcelain enamel as a component of the frit. The spectrophotometric analysis indicated good color stability of cerium oxide enamels.     

Colorimetric characteristics of colored single-coat enamels

Compositions for single-coat glass enamels that allow obtaining a wide color range of coatings with sufficiently good surface quality for steel articles were developed. Different dyes were tested. Properties of the coatings such as the chemical stability, adhesive strength, gloss, and thermal stability were investigated and the firing temperature range, 670–740°C on average, was determined. The colorimetric characteristics of single-coat enamels were calculated. The enamel coatings obtained can be used in mass production.     

CHEMICAL DURABILITY OF PORCELAIN ENAMELS *

The resistance of representative porcelain enamel surfaces to the chemical attack of different concentrations of various solutions was investigated in considerable detail. Cylindrical cup-shaped samples were coated with (1) a ground coat, (2) a white fluoride cover enamel, (3) a white antimony cover enamel, (4) a white zirconium cover enamel, (5) an acid-resistant white cover enamel, (6) a sign blue cover enamel, (7) a blue zirconium enamel, and (8) a chemical acidproof blue cover enamel. The loss in weight of these enamel surfaces, after exposure to chemical attack, was determined at definite time intervals. The solutions studied consisted of different concentrations of the inorganic acids, alkalis, several organic acids, as well as selected salt solutions at both room and boiling temperatures. Numerous curves are presented showing the comparative chemical durability of the various porcelain enamel surfaces in which the cumulative loss in weight is plotted against time. Several photomicrographs show the nature and type of chemical attack on the different surfaces. The porcelain enamel surfaces showed considerable variation in their resistance to the chemical attack of the various solutions. All of the porcelain enamels were, in general, resistant to attack at room temperature by the alkali and salt solutions. The acid-resistant and acidproof enamels were resistant to the action of both inorganic and organic acids at room and at boiling temperatures; a wide variance, however, was shown in the comparative acid resistance of the non-acid-resisting enamel to the attack of either organic acids or inorganic acids at room temperature. AU porcelain enamels showed equally low resistance to boiling alkali solutions, but some of the enamel surfaces were attacked markedly by the boiling salt solutions.     

INFLUENCE OF CHEMICAL COMPOSITION OF ENAMEL ON A FEW OF ITS PROPERTIES

To enlarge the knowledge and data of the relation between the chemical composition of enamel and its properties, many enamels were melted and their acid resistance, viscosity, and opacity were measured. The results have been assembled in graphs representing measurements of these properties in relation to the systematic change of the composition. On the basis of the results, a revision of information is offered relating to the acid resistance of glass and enamel.     

A PRELIMINARY STUDY OF CERAMIC COLORS AND THEIR USE IN VITREOUS ENAMELS1

This report deals with the results obtained from a study of ceramic colors as used in vitreous enamels. Numerous coloring stains were produced and used in various enamel compositions. The batch formulas of the stains are given, and methods of preparation described. To obtain uniformity of texture of the colored enamels, and to insure accuracy of duplication in preparing successive batches of a given stain, it was found desirable to (a) accurately duplicate time and temperature of calcination, and in some cases furnace atmosphere; (a) wash the stains free from soluble matter after calcination; (c) grind and pass them through a fine screen before use; and (d) keep the enamel composition constant. Several of the stains were produced on a relatively large scale and tested commercially under plant conditions. These gave excellent results.     

Use of secondary resources for increasing the chemical stability of glass enamels

The chemical stability of glass enamels obtained with available synthetic and close to synthetic raw materials is investigated. The charge and chemical compositions of two enamels based on available raw materials are presented. The developed enamels are recommended for the chemical and metallurgical industries as acid-resistant coatings.Translated from Steklo i Keramika, No. 10, pp. 30 – 32, October, 1995.     

Tinted one-coat glass enamels for steel

A basic formula for one-coat glass enamel is developed, which makes it possible to obtain a wide color range of coatings for steel products with good surface quality. A number of ionic colorants is tested, mainly compounds of d-and f-elements. The properties of coatings are studied: chemical resistance, adhesion strength, luster, and heat resistance. Their firing temperature is determined. The obtained glass enamels can be used in industrial production. __________ Translated from Steklo i Keramika, No. 1, pp. 28–30, January, 2006.     

Nature of Adherence of Porcelain Enamels to Metals

An investigation of the fundamentals of the adherence of porcelain enamels to metals indicated that good adherence is the result of metal-to-metal bonds between the atoms in the base metal and the proper metallic ions in the enamel. To accomplish this type of bond, the enamel must meet certain chemical and thermodynamic requirements: (1) The enamel at the interface must be saturated with an oxide of the metal and (2) this oxide must be one which, when in solution in the glass, will not be reduced by the metal. In the case of iron, the oxide is FeO. Many of the phenomena observed in commercial enameling were investigated and found to be related to adherence, but not essential for its development. An example is the precipitation of metallic particles in the enamel. Much of the complexity in commercial enameling arises from the limitations imposed by practical considerations. For example, because enamels usually are fired in air, the heavy scale developed during the early stages of firing must be removed before adherence can be developed. Likewise, as the conditions of the enamel-metal interface change rapidly during firing, "adherence-promoting oxides" are used to help maintain the necessary conditions for the time required in commercial enameling. Surface roughness, although not necessary for excellent adherence, was found to improve the apparent adherence when the bond between the enamel and the metal was relatively weak.     

Art enamels for copper

It is shown that colored art enamels for copper can be produced using a single low-melting glass matrix in the R₂O−PbO−B₂O₅−SiO₂ system, and that such enamels can be fired at 680–700°C. Optimum percentages of pigments and oxides are determined for coatings to have various stable colors. The synthesized enamels were tested in the manufacture of household pieces of art. Translated from Steklo i Keramika, No 3, pp. 25–27, March, 1997.     

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.     

Effect of alkali metal oxides on the properties of titanium containing glass enamels

The effect of the ratio of three alkali oxides on the physical and chemical properties of titanium-containing enamels has been investigated and their optimal concentrations have been determined. Acid resistant enamel for steel utensils has been developed. __________ Translated from Steklo i Keramika, No. 7, pp. 25–27, July, 2007.     

Standardizing Shop Practices Relative to Making and Application of Steel Ground Coat Enamels. I

I The effect of manganese dioxide on the physical properties of ground coat enamels is: (1) to give a good gloss; (2) to give a harder enamel; (3) to reduce the coefficient of expansion of the glass in which it is used; (4) when used with cobalt a uniform color desirable in stove work is obtained; (5) no difference in the adhesion of the ground coat between enamels using manganese, cobalt, or combinations of dioxides is apparent; (6) no effect on chipping is apparent; (7) while not absolutely essential in ground coats it is very desirable for use from an economy stand point. II. A theory of ground coat adherence based on the fact that part of the steel is oxidized to iron oxide which is partly absorbed by the fused enamel and into which some of the enamel penetrates is set forth, and an explanation given of various effects obtained. III. Most of the things which should be done to maintain control in making and firing of ground coats for sheet steel are emphasized. IV. The method of control for application of ground coat enamel by weighing the amount of dry enamel on a sheet of metal of known area is described. This is used to maintain a uniform consistency of the enamel. Other essential features which have in the past caused trouble to many enamelers are mentioned.     

Chemical Resistance of Low-Melting Enamels for Decorating Glass Products

The chemical resistance of lead-free low-melting opaque enamels intended for decorating the external surface of household glass is determined depending on the duration of treatment with hot (98°C) water and 2% sodium carbonate solution. The synthesized enamels can be attributed to the class of enamels resistant to hot water and weakly alkaline solutions.     

DETERMINATION OF THE ALKALIS IN VITREOUS ENAMEL1

Sodium and potassium comprise from 5 to 25%, of the total composition of vitreous enamels. The other 75% is comprised of a wider variety of other elements than is found usually in materials which are analyzed for their alkali content. No less than twentyfive oxides are used commonly in enamel glass, and often fifteen of these are in a single enamel. The task of removing all interfering elements from the alkalis is an analytical problem of more than ordinary difficulty. The process is necessarily long and tedious. It calls for the most exact attention to detail and the most careful manipulation. This article tells of attempts to use the usual methods for determination of alkalis in vitreous enamel, and also the procedures found to be most useful and accurate for all classes of enamels.     

THE CAUSES AND CONTROL OF FISH SCALING OF ENAMELS FOR SHEET IRON AND STEEL1

Data obtained.—This paper presents measurements of the following factors and properties and their influences upon fish scaling in the case of typical single and three-coat enamels: time and temp. during melting of the frit; fusibility of the enamel; coeff. of expansion of the enamel, and of a variety of representative irons and steels up to 500°C (accuracy about 0.1%); annealing the enamel coat after firing; chem. comp. of the steels and irons; mechanical treatment (rolling, spinning, drawing, and so forth of the stock; microscopic surface structure of the stock; effect of chem. comp. upon thermal expansion of enamel. Incidentally it was found that the formulas of Mayer and Havas for computing the thermal expansion of enamel from its chem. comp. can not be relied upon: Conclusions.—On the basis of these exhaustive tests, the following conclusions have been drawn as to the causes and the control of fish scaling. (A) Causes.—1. The cause of fish scaling lies in the difference of the coefficients of expansion of the enamel and the stock, that for steel being higher than for enamels so that the latter are under a compressive stress. The factors influencing this phenomenon are as follows: (a) Composition of the enamel as affecting the coefficient of expansion of the enamel; (b) Overfiring—thus volatilizing those substances which tend to keep the coefficient high; (c) Lack of annealing enameled ware, the enamel coating of which is a glass and should logically be treated as such. 2. Fish scaling is due secondarily to a number of factors which may affect the strength of the enamel or its adherence to the metal. (a) The physical condition of the surface of the metal as influenced by drawing, spinning, cold rolling or other mechanical treatment; (b) Composition of the glass as affecting its elastic strength; (c) Underfiring, enamel not fused to metals; (d) Cleanliness of the surface as regards removal of drawing compounds, grease, etc. (B) Remedies.—1. (a) Adjusting the composition of the enamel so as to increase its coefficient, e. g., by decreasing the boric acid content; (b) Correct firing of the enamel to avoid unnecessary volatilization of such fluxes as soda and cryolite; 2. (a) Adjusting enamel composition to increase its strength; (b) Correct firing to give proper adherence. 3. Treatment of metal to give best adhesion by (a) cold rolling or other suitable mechanical treatment of the untreated steel; (b) thorough cleaning. (C) Summary.—Broadly stated, then, fish scaling can be absolutely controlled by one or all of the following methods: (1) By the development of an enamel with an expansion fitting the metal; (2) by annealing the enameled ware; (3) by treatment of the metal as cold rolling or some other method of working: (4) by developing an enamel with a wide range of compressional elasticity and applying this enamel to metal treated as indicated above.     

Effects of two staining methods on color stability of wood flour/polypropylene composites during accelerated UV weathering

Two staining methods of wood flour/polypropylene composites in an attempt to improve the color stability of wood‐plastic composites (WPCs) were investigated. The first was to dye wood flour (WF) before compounding with polypropylene (PP) to make stained composites. The second method involved mixing pigments directly with WF and PP. Nine groups of composites were weathered in a QUV accelerated weathering tester for 960 h. Their surface color, surface gloss, washing resistance, and flexural properties were tested during weathering. Additionally, the weathered surface was characterized by SEM and ATR‐FTIR. The results revealed that (1) the washing resistance of composites were improved after staining treatments; (2) composites made of dyed WF showed higher surface gloss values and less cracks on weathered surface at the early stage of weathering; while composites containing pigments displayed brighter color, less color change, and less loss of flexural properties during weathering; and (3) weathering resulted in the protrusion of WF and photodegraded lignin on exposed surface. Adding pigments was proven to be more effective staining method for improving composite color stability during weathering. POLYM. COMPOS., 38:1194–1205, 2017. © 2015 Society of Plastics Engineers     

MOLYBDENUM IN ENAMELS: I,ADHERENCE PRODUCED WITH MOLYBDENUM COMPOUNDS*

When definite types of white or clear enamel are milled with certain molybdenum compounds, light-colored ground coats are produced. These ground coats show excellent adherence when applied in the usual manner to deeply pickled sheet steel. Firing may be done at 1600 °F. or at 1500 °F., according to the type of enamel. The paper also discusses the properties of molybdenum compounds, the problems involved in their use, the types of compounds which produce adherence, the type of enamels which work successfully, and a possible explanation of how these compounds function to produce adherence.     

AGREEMENT OF GROUND COAT AND ENAMEL1

Troubles in working with enamels may be caused by poor workmanship in some department or by changes in composition of the enamel due to differences in chemical composition of raw materials used. The application of Staley's refractory ratio in determining the agreement of ground coat and enamel cover coat is illustrated.     

Color Stability of Clear and Opaque Titania Enamels Containing Various Color Oxides

A study was made of the spectrophotometric characteristics of a clear and an opaque titania-bearing enamel. Three and six per cent additions of green, blue, brown, and red oxides were made to the base enamels. After firing the enameled samples over a range of time and temperature, spectrcphotometric and X-ray data were obtained. The results indicate that the lack of stability of the opaque colored enamels is due to the change from a blue-white to a cream-white color on increased firing treatment. The addition of a cream component tends to shift the hue of the fired enamel toward the red end of the visible spectrum. The green and the blue colors were much less stable than the red. X-ray data show that the total anatase present decreases, which is evidence that a cream-white color developed. X-ray data did not indicate any change in crystal structure of the anatase, rutile, or color oxide. Titania present in the glass of the clear enamel did not cause color instability.     

浅谈粉彩艺术

粉彩是景德镇窑在五彩的基础上及"珐琅彩"的影响下创制成功的又一种彩瓷。它的独特之处在于彩绘时掺加一种白色的彩料"玻璃白"。"玻璃白"具有乳浊效果,画出的图案可发挥渲染技法的特性,呈现一种粉润的感觉,因此被称为"粉彩"或"软彩"。