Nolifrit Brief Analysis on Viscosity of Enamel

Viscosity is a measure of the resistance of a liquid to flow. The greater the viscosity, the smaller the fluidity, and the unit of viscosity is Pa•s.

Enamel frit is similar to glass and has no constant melting point. The solid enamel layer is gradually softened and converted into a melt under the condition of constant heating. Therefore, the viscosity of the enamel is continuously changed, and there is no numerical mutation. This is different from crystals. When the crystal is heated to the melting temperature, its viscosity changes abruptly.

Nolifrit Brief Analysis on Viscosity of Enamel

In the first stage of enamelware firing, enamel powder layer decreases in viscosity with increasing temperature; in the later stage of firing, the enamelware gradually cools and the viscosity increases with decreasing temperature. When the viscosity reaches or exceeds 1012 Pa•s, the molten enamel layer becomes a solid enamel layer.

At a typical firing temperature, the enamel melt has a viscosity of 200 to 400 Pa•s.

The viscosity of the enamel depends mainly on the chemical composition of the enamel. The influence of the composition of the enamel on the viscosity is very complicated. The composition and content of the oxide are different, and the influence on the viscosity of the enamel is different in different temperature ranges.

Enamel frit manufacturer found that the introduction of monovalent alkali metal oxides, B2O3 and fluoride in the enamel can reduce the viscosity of the enamel melt; the introduction of SiO2, Al2O3, CaO, MgO, etc., makes the viscosity of the enamel melt increase. When the content of TiO2 in the formulation does not exceed 8%, the viscosity of the enamel melt is lowered; when the content exceeds 8%, the viscosity of the enamel melt is increased.

Milling additives like quartz, zirconium silicate, feldspar, titanium oxide, tin oxide, clay, etc., can not be completely dissolved in the enamel in short firing time and at lower temperature, so this makes viscosity of enamel melt improved.

The enamel with high viscosity is not conducive to the escape of gas in the enamel layer during firing, which increases the pores and bubbles of the enamel layer, and is not conducive to the flow of the enamel melt during firing, which tends to cause the fineness and gloss of the enamel surface to decrease. For enamel products requiring high-temperature firing, enamel with high viscosity is beneficial to improve the burning resistance and firing range of enamel products.

Ceramic Enamel Frit

20190528Available in a variety of colors to harmonize or contrast with the vision area, the ceramic enamel frit is applied to the surface of the glass. Ceramic enamel frits contain finely ground glass mixed with inorganic pigments to produce a desired color. The coated glass is then heated to about 1,150°F, fusing the frit to the glass surface, which produces a ceramic coating almost as hard and tough as the glass itself. A fired ceramic enamel frit is durable and resists scratching, chipping, peeling, fading and chemical attacks.

Application

Spandrel glass can be installed monolithically, using insulated metal backpans, but is more often found as a component of an insulating glass unit. Reflective spandrel glass units are widely used when a uniform all-glass look is desired for the building exterior. Typical applications include commercial fixed windows, curtain walls, storefronts and wall cladding. Spandrel glass is traditionally an opaque material not intended for use in vision areas.

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The Porcelain Enamel Industry

Porcelain enamel has been around for 4000 years and shows no signs of disappearing any time soon. Although alternative materials like stainless steel, plastics and paints continue to gain market share and have completely taken over some markets, such as dishwashers, the cooking and laundry appliance markets remain strong, and total frit production remains about the same. However, some manufacturers believe a huge revolution in materials technology is needed to ensure the continued success of the industry. Both suppliers and manufacturers are doing their share to help ensure that this revolution takes place.

Porcelain enamel coatings are made from a frit based on low melting temperature (2000 to 2500°F) borosilicate glasses. After the glass raw materials are melted (generally in recuperative furnaces) at rates ranging from 5 to 50 tons per day, rapid quenching is used to shatter the resultant glass into small particles. Further particle size reduction is achieved by grinding. The coating is applied using wet suspension or dry electrostatic powder processes, and is then heated to about 1500°F to produce chemical bonding with the metal substrate.

Pre-milled frits now allow enamelers to custom blend their own enamel formulations without using costly milling equipment. The enameler can blend the exact amount required for the job, eliminating waste. Blends can be made almost “just in time,” eliminating the need for a large wet enamel inventory.

Many frit manufacturers have switched from air/gas to oxygen/gas combustion systems to lower their emissions, and this trend is expected to continue. Smelters have become more automated, and larger capacities are being used as product volumes increase through the increased standardization of frits.

For instance, unique appearance characteristics are under development, including metallic lusters to simulate copper metal or stainless steel appearances. Refinements in frit products are also being made to achieve “easy to clean” oven coatings, as well as infrared reflectivity for faster cooking. In addition, hybrid coatings are being investigated to take advantage of properties provided by both porcelain enamel and organic coatings.

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High-Temperature Porcelain Enamel Coating

To attach a porcelain enamel coating to any substrate by enameling, both substrate and glass must be heated to the fusion temperature of the glass. However, fusion methods have not been successful for the more refractory materials. Because most refractory porcelain enamel coatings are amorphous or crystalline in nature, they have to be applied by relatively novel techniques.

Although most ceramic materials are refractory, some of them can be vaporized in an electric arc or hot vacuum. Thin porcelain enamel coatings of amorphous silica can be applied readily to relatively cool substrates by vaporizing metallic silicon or silicon halides in the presence of small quantities of oxygen. Apparently the transfer is accomplished largely as silicon monoxide, which recombines with oxygen on cooling. The process is used to obtain thin, protective, optically transparent films on lenses, certain electrical components, and metal reflectors.

Other porcelain enamel coatings may be produced by vaporizing one or more components of the coating. In this way porcelain enamel coatings of the respective carbides of silicon, boron, aluminum, and chromium can be deposited on graphite, silicon nitride can be formed on metallic silicon, and silicide coatings can be deposited on metals such as tungsten and molybdenum. These processes are necessarily expensive and are poorly adaptable to large specimens or complex shapes.

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Porcelain enamels and ceramic coatings

Earlier definitions of ceramic materials usually stressed their mineral origin and the need for heat to convert them into useful form. As a consequence, only porcelain enamels and glazes were recognized as ceramic coatings until recently, when the principles of phase relations, bonding mechanisms, and crystal structure were applied to ceramic materials and to coatings made from them. In consequence, ceramic materials can now be most safely defined as solid substances that are neither metallic nor organic in nature, a definition that is somewhat more inclusive than older ones, but more accurately reflects modern scientific usage.

Most ceramics are metal oxides, or mixtures and solutions of such oxides. Certain ceramic materials, however, contain little or no oxygen. As a whole, ceramic materials are harder, more inert, and more brittle than organic or metallic substances. Most ceramic coatings are employed to exploit the first two properties while minimizing the third.

Low-Temperature Coatings

The outstanding resistance to corrosion of certain metals, notably aluminum and chromium, is attributable to the remarkable adherence of their oxide films. Aluminum does not corrode because its oxidation product, unlike that of iron, is a highly protective coating. It was once believed that some mysterious kinship between a metal and its own oxide was needed for this protection, but recent knowledge relating to the structure of metals and metal oxides has enabled metallurgists to develop alloys that form even more stable and adherent films. Methods for thickening or stabilizing these oxide coatings by heat treatment, electrolysis, or chemical reaction are widely accepted.

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Cadmium Color Pigments

Cadmium color pigments are stable inorganic colouring agents which can be produced in a range of brilliant shades of yellow, orange, red and maroon. Their greatest use is in plastics but they also have significant application in ceramics, glasses and specialist paints.

Modern day Cadmium color pigments are carefully engineered products manufactured in regulated chemical plants with full Health and Safety and Environmental permits under responsible care management. They are calcined to a high temperature to convert to the stable hexagonal form before then undergoing a series of further processes resulting in highly stable pigment grade products with controlled particle size, surface area and surface treatment to ensure they are not only correct for colour but also meet extremely low solubility limits.

Cadmium color pigments are specific Cd compounds, with different CAS numbers and REACH registration files.

These substances are specifically excluded from the classification and labelling entries in the DSD and GHS tables covering cadmium compounds. A risk assessment of these products conducted by the EU concluded that these products offer no significant hazard to either human health or to the environment. REACH registration has confirmed that no hazard classifications apply – either for human health or to the environment.

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Transparent Frit

Owing to rich industrial experience in this domain, we are involved in manufacturing and supplying a wide assortment of Transparent Frit. This Transparent Frit is extensively used in garden (paving) and square, river decoration. Moreover, these products are available in the market in bulk in various sizes.

Taking advantage of the latest infrastructure facility possessed by us, we exporting and supplying the most sought after range of Ceramic Frits and Ceramic Glaze Frits. The wide range of products offered by us include Ceramic Frits, Tiles Frits, Ceramic Glazes, Ceramic Glazes Frits, Abrasive Bonding Frits and Glass Ceramic Frits that are used in various industrial sectors. These products are designed and developed in our advanced manufacturing unit. We make use of the finest grade quality raw materials that are procured from reliable vendor base of the industry. The entire range of products offered by us in the international market segments for their cost effectiveness.

Banking on our enriched industry experience, we are able to gain a good understanding of the diverse application needs of the ceramic industry and offer suitable range of products.

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Safety Issues of porcelain enamel

Now for the safety issues. Porcelain enamels are very fine particles and it is important that you use every precaution when handling this product. This involves not only how they are stored, but care when using this powder. Containers that are airtight with a clear top should be used for storage purposes.

These minute razor-sharp pieces of glass can be easily breathed in and it is vital that a respirator with sufficient NS rating – NS97 and good ventilation are available during usage. Wear a respirator when cleaning up an area and use only wet rags, damp wipes, or moist paper towels. Use good judgment in handling this potentially dangerous material.

Your product should have come with the Material Safety Data Sheet from OSHA. Read it for any safety precautions and information. Remember when learning how to porcelain enamel be safe!

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White Enamel Powder for Overglaze Painting

White Enamel for Porcelain, in white powder form in large, 2 dram glass vial with screw on lid.

This White Enamel Powder for all overglaze painting has a high relief and will not pop off. Use the OJ3, Pollyanna Medium for both enamel and raised paste work. Mix to a thick toothpaste consistency with this medium. Then add one drop of pure turpentine at a time until strings. It will make wonderful dots, scrolls – then thin with more turpentine to make longer, even lines (won’t be quite as raised if thinned more) Fire to Cone .017, – .018 1443 – 1386 F, 784 – 752 C

You can add any regular overglaze paint to the enamel to make your own colors! Add the color after the mixture strings – you may have to add some more turpentine (never add more of the medium as that will make it flatten more!) Do not add gold over this Enamel. Use the JTX Josephine Texture Paste – Base for Gold for a white, raised relief which can be covered with Gold or Silver.

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Spotlight on cadmium red

Think of the colour red and most likely you will find yourself thinking of the big emotions and that is why artists like it so much. Red is an extremely dominant colour and even a small piece in a painting will catch your attention. It is the colour most often associated with powerful feelings such as love, passion and anger as well as heat, fire and blood. Cadmium red is a very strong, warm and opaque red and in the early part of the 20th century became a natural replacement for the distinctive but toxic vermilion.

Cadmiums have the broadest range of hues derived from any of the inorganic pigment groups. These hues range from pale to golden deep yellows, light fiery to deep oranges through to light bright scarlets to deep reds and maroons.

Moving Into The Red

It was some time after the introduction of cadmium yellow that cadmium red began to appear. The early reds were made by heating the cadmium yellow together with selenium. In 1919 a patent was registered for the production of cadmium orange and cadmium red. The method for this production was to mix cadmium salt solutions with alkali and alkaline earth sulphides and, in turn, to heat the resultant precipitate. For those of us who might not have been paying attention in our chemistry lessons: a precipitate is the solid material or collection of particles that is left in a solution after a chemical reaction and, not surprisingly, the process itself is called precipitation.

Advanced Production Techniques

The production of modern, high performance cadmium red is an expensive and lengthy process requiring only the purest raw materials to produce the best possible colour.

Transforming the cadmium metal into a usable pigment means it undergoes several carefully controlled chemical reactions and procedures using various ingredients including mineral acids, sodium sulphide flakes, water, and selenium. Towards the end of the process heating takes place to create the pigment and it is in this heating process that the quality and hue of the final pigment begins to form. The emerging pigment is then ground down into tiny particles – these grinding processes affect the way the pigment interacts with light. Fine particles have a good diffused reflection and produce a colour that is very strong and vibrant.

Safety

Cadmium itself is a heavy metal and is toxic but cadmium pigments are not classified as dangerous for use in line with EC classification. The level of soluble cadmium in the pigments is so low that no hazard warnings are needed and they pose no greater risk after swallowing or breathing in than other pigment types. Cadmium pigments are restricted for certain applications but this restriction does not apply to artists’ colours.

Go Red

Cadmium red will add brightness, strength, opacity and maybe a touch of passion to any artist’s work and is now widely regarded as a viable alternative to the erratic and toxic vermilion either natural or synthesised. Available from Winsor & Newton Artists’ Oil Colour: Cadmium Red and Cadmium Red Deep.

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