Porcelain Enamel History

Down through the ages, artists, inventors and scientists have searched for materials that are both beautiful and enduring.

The Egyptians inlaid glass in metal frames in 2000 BC. Greek craftsmen advanced the art form by applying sufficient heat to fuse the metal and glass. With the expansion of the Roman Empire, the technology spread throughout Europe.

The continued existence of these artifacts fashioned centuries ago, is testimony to the timeless beauty and permanence of Porcelain Enamel.

Though all of us use porcelain enamel products everyday, it is something that few of us are aware of on a conscious level. We bathe in porcelain enamel bathtubs. Use porcelain enamel sinks, lavatories, stoves, ovens, washing machines, dryers and water heaters without a thought about that beautiful, glassy finish.

We walk through buildings sheathed in porcelain enamel and read signs of porcelain enamel. The operating rooms of many hospitals are porcelain enamel. Our children write on porcelain enamel boards at school, and we barbecue on porcelain enamel grills. It is present in an amazing number of applications that we encounter in our daily schedule.

Porcelain Enamel Cookware

Pots and pans made of materials, such as cast iron or aluminum that have had porcelain enamel applied as a coating. It prevents them from corroding or reacting with the food being cooked in them. A pan coated with porcelain should not be used for sautéing or frying but will work as a saucepan or roaster.

To care for porcelain enamel cookware, wash with hot soapy water. A nylon scouring pad, nylon scraper, or nonabrasive cleaner can also be used to help remove stuck on food. Porcelain enamel can be cleaned occasionally in the dishwasher unless it has a non-stick interior surface, but dishwasher use should be limited to avoid dulling the enamel surface.

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Cobalt blue pigment

Brief description of Cobalt blue pigment:

It’s a cobalt oxide-aluminum oxide. Very costly and extraordinary stable pigment of pure blue colour discovered by Thénard in 1802. It is now the most important of the cobalt pigments. Although smalt, a pigment made from cobalt blue pigment glass has been known at least since the Middle Ages, the cobalt blue pigment established in the nineteenth century was a greatly improved one.

Example of use by artists:

A painting witnesses Renoir’s shifts from cobalt blue pigment to the new and more cheap artificial ultramarine

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This painting was painted during the restless period in Renoir’s work. It is immediately apparent that the picture exhibits two distinct styles. The group of figures on the right is painted in a soft feathery style reminiscent of his work of the later 1870s, while the umbrellas and the couple on the left are painted in a harder manner with more distinct outlines and subdued steely colors. The exact date of the painting is not known, but it is generally accepted that it was worked on over a period of several years.

Notice how the fashions illustrated in the Umbrellas differs. The women in Renoir’s paintings are usually dressed in the latest styles. The dresses and hats worn by the figures at the right conform to a fashion that appeared in 1881 and which became popular in 1882. The vogue was superseded the following year by a more sever style of dress with simple straight lines. THe woman with the band-box is dressed in this latter style which was the height of fashion in 1885-6, but which had fallen out of favor by 1887.

Renoir appears to have changed his palette significantly between the two stages. Examination of the cross-sections has shown that in the earlier phase he used exclusively cobalt blue pigment, available from 1802, his habitual choice during the 1870’s and early 1880’s, but in finishing and revising the composition he used only artificial ultramarine which came in use in the 1870s.

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Using ceramic pigment

Depending on the use, ceramic pigments may be used straight and just mixed with water, but they are more commonly added as colorants in clay bodies and glazes. Some ceramic pigments are specifically formulated for clay bodies while some are not suitable at all. When used in clay, ceramic pigments are usually used in engobes and slips as a coating for clay rather than pigmenting the entire body. The exception to this would be using stains to tint porcelain for neriage work.

Use in concentrations of 10–15% in clay, using more or less depending on the intensity needed. Add the ceramic pigment to the slip and sieve through a 120x mesh screen to ensure adequate dispersion.

Ceramic pigments can be used in underglazes for brushing onto greenware or bisque. If used only with water as a medium, some glazes may crawl, so for best results, mix the stains with a frit (for example, Ferro frit 3124). Begin with a mix of 85 frit/15 ceramic pigment and test. Transparent gloss glazes applied over the top will heighten the intensity of the colors.

When using ceramic pigments in glazes, usually in concentrations of 1–10%, a little more care must be taken because some ceramic pigment systems react with materials in a glaze. Some ceramic pigments are affected by the presence, or lack of, boron, zinc, calcium, and magnesia. Manufacturers provide information on specific reactions. While most ceramic pigments can be used in both oxidation and reduction atmospheres, some are limited to certain maximum temperatures. Again, this information is available from manufacturer websites.

To achieve a wider palette, most ceramic pigments can be mixed to achieve even more colors. The exception is that black ceramic pigments cannot be used to obtain shades of gray because blacks are made from a combination of several metallic oxides. If low percentages are used, the final color is affected by the predominant oxide in the black ceramic pigment.

This article comes from ceramicartsnetwork edit released

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.

This article comes from dentalcare edit released

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