The Low Down on Pigments for Ceramic

Pigments for ceramic, often referred to as ceramic stains, have vastly opened up the color possibilities for potters. And as we all know, adding color to your ceramic art can be a tricky proposition. Unlike working with paints, the raw glaze you put on your prize pot or sculpture often looks completely different from the fired result. So it helps to have a good understanding of all of the options out there for ceramic artists. In this post, we provide the lowdown on pigments for ceramic.

Prepared pigments for ceramic, commonly referred to as ceramic stains, expand the potter’s palette with infinite possibilities. Pigments provide a wide range of color possibilities in clay bodies, inglazes, underglazes, and onglazes.

In order to get a full range of consistent ceramic colors, pigments are used with metallic oxides and salts, many of which are soluble or toxic, to make them stable. By combining these elements, along with clays, silica, and alumina, the industry has come up with 44 different calcined pigment systems covering the entire color spectrum.

Pigments for ceramic solve some of the problems found in using just plain oxides. For example, when pure chrome oxide is used as a colorant to obtain green, it may fume or volatilize in the kiln leading to absorption into the kiln bricks and shelves. The oxide may also effect the color of the glaze. If tin is present in a white or pastel glaze, the chrome reacts with the tin to create a pink coloration. In addition, if any zinc oxide is present in the glaze, you’ll get a dirty-brown color. The solution is to use a green ceramic pigment, of which there are several. One such system is the cobalt-zinc-alumina-chromite blue-green pigment system, where varying the amounts of cobalt and chrome oxides produces a range of colors from green to blue-green to blue.

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Cadmium Red Pigment

Cadmium Red pigment is cadmium zinc sulfoselenide (CdS, CdSe) produced by co-precipitating and calcining, at high temperature, a mixture of cadmium sulfide and selenide sulfide in varied ratios forming a partially crystalline structure.

Details

Cadmium Red pigment is cadmium zinc sulfoselenide (CdS, CdSe) produced by co-precipitating and calcining, at high temperature, a mixture of cadmium sulfide and selenide sulfide in varied ratios forming a partially crystalline structure with sometimes hexagonal or cubic forms. Cadmium pigments are the most durable yellow, orange and red inorganic pigments commercially available. They have excellent chemical and heat stability, and can be used in chemically aggressive environments and durable applications without color fade.

Cadmium sulfoselenide pigments were developed in response to the need for stable shades of cadmium orange to red colors. Cadmium and selenide salts are co-precipitated and then heated to 300 °C.

Uses

Most cadmium pigments are used in plastics. These pigments disperse well in most polymers to give high opacity and tinting strength. The pigments are insoluble in organic solvents, have good resistance to alkalis and in most cases will remain lightfast for the life of the plastic. As a result, cadmium pigments have been used in a wide range of plastic products. Nowadays, their greatest application is in complex polymers which are processed at higher temperatures and require the unique durability and technical performance of a cadmium pigment. Their use is almost mandatory in many nylon, acrylonitrile butadiene styrene (ABS), polycarbonates, high density polyethylene, silicone resins and other modern thermoplastic polymers processed at high temperatures which preclude the use of organic pigments and also most alternative inorganic pigments in the range of hues provided by cadmium. Cadmium pigmented engineering polymers such as ABS are widely used in products which include telephones, gas pipes and fittings, electricity cables, beverage crates and motor vehicle radiator fans.

Bright cadmium yellows, oranges and reds are major pigments for artists’ colors where their permanence and opacity are the accepted standards against which other pigments are judged. Cadmium yellows and reds can have service temperatures well above 300 °C and are used in coatings for process chemical and steam pipes. They can also be incorporated in latex and acrylic coatings.

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Enamel Structure and Composition

Enamel is the most mineralized tissue of the body, forming a very hard, thin, translucent layer of calcified tissue that covers the entire anatomic crown of the tooth. It can vary in thickness and hardness on each tooth, from tooth to tooth and from person to person. It can also vary in color (typically from yellowish to grayish white) depending on variations in the thickness, quality of its mineral structure and surface stains. Enamel has no blood or nerve supply within it. It is enamel’s hardness that enables teeth to withstand blunt, heavy masticatory forces. Enamel is so hard because it is composed primarily of inorganic materials: roughly 95% to 98% of it is calcium and phosphate ions that make up strong hydroxyapatite crystals. Yet, these are not pure crystals, because they are carbonated and contain trace minerals such as strontium, magnesium, lead, and fluoride. These factors make “biological hydroxyapatite” more soluble than pure hydroxyapatite.

Approximately 1% to 2% of enamel is made up of organic materials, particularly enamel-specific proteins called enamelins, which have a high affinity for binding hydroxyapatite crystals. Water makes up the remainder of enamel, accounting for about 4% of its composition.

The inorganic, organic, and water components of enamel are highly organized: millions of carbonated hydroxyapatite crystals are arranged in long, thin structures called rods that are 4 µm to 8 µm in diameter. It is estimated that the number of rods in a tooth ranges from 5 million in the lower lateral incisor to 12 million in the upper first molar. In general, rods extend at right angles from the dento–enamel junction (the junction between enamel and the layer below it called dentin) to the tooth surface. Surrounding each rod is a rod sheath made up of a protein matrix of enamelins. The area in between rods is called interrod enamel, or interrod cement. While it has the same crystal composition, crystal orientation is different, distinguishing rods from interrod enamel.

Minute spaces exist where crystals do not form between rods. Typically called pores, they contribute to enamel’s permeability, which allows fluid movement and diffusion to occur, but they also cause variations in density and hardness in the tooth, which can create spots that are more prone to demineralization – the loss of calcium and phosphate ions – when oral pH becomes too acidic and drops below 5.5. In demineralization, the crystalline structure shrinks in size, while pores enlarge.

Enamel is formed by epithelial cells called ameloblasts. Just before a tooth erupts from the gums, the ameloblasts are broken down, removing enamel’s ability to regenerate or repair itself. This means that when enamel is damaged by injury or decay, it cannot be restored beyond the normal course of remineralization. When a tooth erupts, it is also not fully mineralized. To completely mineralize the tooth, calcium, phosphorous, and fluoride ions are taken up from saliva to add a layer of 10 µm to 100 µm of enamel over time.

There are conditions that can affect the formation of enamel and thus increase the risk of caries. These include the genetic disorder amelogenesis imperfecta, in which enamel is never completely mineralized and flakes off easily, exposing softer dentin to cariogenic bacteria. Other conditions are linked with increased enamel demineralization, such as gastroesophageal reflux disease (GERD) and celiac disease.

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Fusing With Frit Glass Powder

Frit glass powders come in a rainbow of colors to choose from. Any size of compatible glass frit will work. The outcome will be different depending on the size and combination you use to mix with the frit.

Before you mix your colors, you will want to do a color test first. Mixing colors can sometimes turn to mud on your finished piece, so test first.

When fusing with frit glass powders, they can also be used dry. You can use stencils to apply the frit glass powder.

This method can be a little tricky, since having to lift the stencil can be difficult and messy. If you do try to use stencils with your frit glass powders, try using a quick spray of a pump bottle hairspray to keep your powders where you want them.

When applying only dry powders, be sure to wet pack. You can sprinkle it on with your finger tips or load a decorator with the powder and apply.

Once you have the powder in the area that you want, mist the finished piece with thinned glue (Elmer’s). Now push gently down on the design so that it bonds. Otherwise the powders ball up into the center during fusing, unless you want this effect in your fusing project.

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Polyester Colour Pigment

Colour pigment dispersions in a wide range of colours designed specifically as a gelcoat pigment, polyester resin pigment, fibreglass resin colour pigment, polyester laminating pigment and casting resin pigment.

Using heavy duty triple rolling mills, colour pigment dispersions are of high quality homogenous consistency ground down to particle sizes less than 10microns, giving the maximum colour for the least colour pigment possible, limiting the impact of the colour pigment on the structural performance of a resin.

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Safety and Benefits of Using Enamel Coating Cast Iron Cookware

While traditional cast iron cookware is still an essential part of any kitchen the majority of cooks and chefs prefer the enameled version. Enamel coating cast iron is much easier to clean and there are no seasoning issues. The inner coating provides non-stick properties and prevents iron leaching into your food. This cookware pieces come in a variety of vibrant colors to meet customer expectations and to match existing colors in kitchen design.

Is Enameled Cast Iron Cookware Safe?

lt in iron rising to toxic levels. Excess iron levels in the body can lead to serious health problems.This, of course, isn’t a problem with enamel coating iron. The main benefit of enamel coating pieces over traditional cast iron vessels is their inertness. The enamel coating is non-reactive, so you can cook all types of foods in those pots. Once the enamel coating has been removed from the interior surface, it may no longer be inert, and cast iron in the pot’s core will leech into the food.

Enamel coating iron cookware is considered safe, according to the FDA’s Center for Food Safety and Applied Nutrition. The lines of cookware imported from abroad must meet the FDA safety standards. The importation of products that contain potentially toxic substance cadmium in their glazes is prohibited and manufacturers have discontinued use of cadmium-based and lead-based pigments.

To ensure the safety of your cookware buy only good quality enamel products from a trusted brands. The coating must be thick enough that it won’t easily chip. Avoid bringing in glazed cast iron vessels from abroad.

Advantages

The following are some advantages that enamel coating cookware offers:

Enamel cast iron cookware is healthy and safe to use. Unlike pure cast iron, this utensils don’t interact with your food, so you can cook any type of food in them including tomatoes and other acidic foods.

Enamel coating provides a non-stick surface that makes cooking easy without food sticking to the bottom.

Enameled cast iron pieces are extremely durable. The products last for many years and can be passed from parent to child.

The pans and pots can be heated to high temperatures, which makes them a popular choice for searing and braising foods.

Cast Iron construction conducts and holds heat very well, providing an even consistent temperature throughout the entire pot, which is perfect for cooking soups, stews and chili.

Superior heat retention is helpful in keeping the food warm when serving. These pans only need a low to medium heat, which makes this type of cookware energy efficient.

This cookware is suitable for all heat sources and any type of stove top. It is also acceptable for refrigerated food storage and can be used as a serving dish on the table.

The enamel glazed surface does not need any kind of seasoning, so it requires very little maintenance. Enamel glaze also prevents rusting and comes in various colors for visual appeal.

This article comes from healthy-cookware edit released

Efcolor Enamel Powder

Efcolor low temperature enamel powder can be used on metal, glass, wood, porcelain, ceramic, stone, and other materials. No kiln required, Efcolor hardens at 150 °C and can be fired in a domestic oven, hotplate, or the Efcolor tea-light stove. Will withstand temperatures up to 180 °C.

Enamel Applications and Preparation

For more than two thousand years, goldsmiths have fused glass onto their work for color enrichment. Wonderful enameled work can be found from many ancient cultures, providing familiar icons of the technical skill and aesthetic sensibilities of their makers.

In our own century enamel has benefited from scientific and industrial research and because of this it has grown from being just one element of the goldsmith’s art to a position of prominence on its own. One need only think of enameled housewares, architectural trim and utilitarian objects to understand the importance of enamel in our society.

For a complete description to enamel the reader is referred to books specifically on that topic such as Kunsthandwerkliches Emaillieren by Erhard Brepohl, third edition, VEB Fachbuchverlag, Leipzig, 1983. But even those who do not intend to incorporate enamels in their work as a primary element should have an understanding of the historical importance of enamel and a general idea of the process. It is for those people that the following pages are included here.

enamel is a simple process that uses very little specialized equipment. The electric kiln in which the metal is brought up to temperature is the single most expensive piece of equipment, and even this has the advantage of lending itself to several other uses in the studio. Of far more importance and requiring greater skill is the preparation of a piece preliminary to enamel. Without intelligent design and proper goldsmithing work, enameled pieces are simply colored bits of metal.

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Ceramic Enamel Frit

Available 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 ceramic enamel 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.

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.

Spandrel Paint Colors: Oldcastle BuildingEnvelope® offers a complete line of ceramic enamel frit in the following standard color options: White, Charcoal, Solargray®, Solarbronze®, Gray Black, Black, Solex®, Ford Blue, Lava Bronze, Warm Gray and EverGreen™. Custom colors for ceramic enamel frit are also available.

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Enamel Solutions

WHAT IS ENAMEL?

Borosilicate glass that may contain aluminum oxide, titanium dioxide, zircon dioxide, phosphorus pentoxide, fluorine, etc. depending on the area and characteristic of use of oxides of sodium, potassium, lithium, barium, calcium, zinc, magnesium, strontium, etc. is fritted either in powder or liquid form. This process results in the coating material known as enamel.

ELECTROSTATIC AND CONVENTIONAL FRITS

  • Primer Frits
  • Top Frits
  • Super Opaque Frits
  • Semi-opaque Frits
  • Self-Colored Frits
  • Acid-resistant Primer and Top Frits
  • Heater Frits
  • Strong Acid-resistant Frits for Special Uses
  • Transparent and Semi-transparent Frits
  • Easy-clean Frits
  • Majolica Frits
  • Two-layer Single-fired Frits
  • Pyrolytic and Catalytic Frits
  • Mill Additives

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