Processing of porcelain enamel powders for electrostatic spraying

Following a brief review on current technology of electrostatic spray for enameling, the requirements on powder properties were discussed.

The use of poly (siloxanes) or poly (silanes) as encapsulants for producing electrostatic porcelain enamel powders with appropriate electrical resistivity, hydrophobicity and fluidity was analyzed from a mechanistic standpoint.

Experimental results were presented to illustrate typical processing problems such as the change of powder properties on aging as a result of differential encapsulation of glass components. Various measures were proposed for improving the stability of powder properties. Optimization of powder processing parameters by means of experimental design technique was described.

This article comes from sciencedirect edit released

Metal Pigment Powders

These metal pigment powders give the ultimate metallic leafing finish in resin & you will want to use them continuously.

It is available in 4 shades, sold in one size container which carry the same volume though each metal pigment powders weight is different.

Using only a smalll amount into your resin mix you can achieve the most amazing of metal looking finishes.

Copper Fine 36 (50g) – Is a beautiful copper metallic with an amazing finish that can be achieved to look like real copper.

Rich Gold Fine 36 (50g) – Is a beautiful rich gold metallic with an amazing finish that can be achieved to look like real gold.

Rose Gold fine 36 (50g) – Is a beautiful rose gold colour which will be a perfect addition to add that wow to your art work.

Aluminium Bright (15g, same volume as the others, its just very light) – This is a brilliant silver leafing grade offering a reflective sparkle to your work (not suitable for polyurathane resins – epoxys only)

This article comes from arttreecreations edit released

Chemical and Physical Properties of Inorganic Pigments

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Inorganic pigments play double-duty as fillers that provide a greater benefit than simple coloration of a formulation; they also impact physical properties of the film during application and throughout the product lifecycle. Pigments in coatings protect the resins and binders from electromagnetic or thermal degradation due to their reflectance of short-wave IR radiation, which also helps to keep the materials containing said pigments cooler.1

Why We Use Pigments

Before we can understand best practices for dispersing materials containing pigments, it is important to understand what a pigment is, and the chemical and physical reasons why we use pigments. Inorganic pigments are transition metal complexes,2 primarily oxides of crystalline or semi-crystalline repeating units of ceramic crystal lattice structure.

The d-orbital of the metal ions is responsible for a multitude of inorganic pigment properties, including color, reactivity, strength (as in Mohs hardness) and weatherability. Pigments are unique as fillers in that they are composed of transition metals surrounded by ligands (functional groups). The way in which the d-orbital of the metal ion interacts with the various ligands to which it is bonded also influences pigment properties; ligand substitution results in modified pigment characteristics.

As an interesting aside, the metal ion-ligand coordination complexes of pigments used in coatings function (that is to say, provide a visible output color) much like light-harvesting complexes in photosynthetic pigments. Drawing from the Stark-Einstein law, we will take this full circle. The law states that an absorbed photon will initiate a primary chemical or physical reaction within the system.3 For coating pigments, this means that the d-orbital of the transition metal experiences excitation; the degree to which this excitation increases the energy gap dictates corresponding perceived color of the material. For example, the transition metal Vanadium can form complexes of four different ionization states (i.e., V2+, V3+, V4+, V5+), which offer pigments of different hues from purple (V2+) to yellow (V5+).4

That is to say, to reduce agglomerates to aggregates requires one-tenth the energy of reducing aggregates to primary particles; aggregates are chemically bound. Surfactants physically bond to aggregates/primary particles and prevent the reformation of pigment agglomerates by disruption of the London-Van der Waal forces. It must be noted that the geometry of the particles plays a role in the extent to which these forces are felt over a specific distance. Surface defects and aspect ratios other than one result in an increased surface area-to-volume ratio, which entails a greater Van der Waal force of attraction than simple spheres; the probability of the geometry leading to mechanical interlocking is also increased.

Understanding Dispersion

Dispersion is a physical process that tends to increase the entropy of a system. A poorly stabilized dispersion will tend to flocculate; a state that decreases the potential number of conformations of the system (i.e., reduced entropy or randomness). This is largely due to the randomized Brownian motion of the dispersed particles, which are attracted (i.e., tend to agglomerate) via short-range London-Van der Waal forces.

For adequate dispersion it is essential that the surface tension of the liquid(s) be less than the surface free energy of the pigment (and other solids, such as fillers). If a specific solvent, resin or other liquid is to be used with a solid that it does not have an affinity for -in the sense of it being difficult to incorporate and wet out -surfactants are utilized to mitigate de-wetting and prevent floccules from forming.

This article comes from pcimag edit released

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.

This article comes from recipetips edit released

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.

This article comes from webexhibits edit released

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