Patina is the natural aging of metals, including copper and brass. It occurs when copper is exposed to oxygen. Many artists deliberately add patina chemicals as part of the initial design and finish of artwork and antique furniture or to imitate antiquity in newly-built items. A wide array of chemicals, both synthetic and organic, are used to create varying patina effects on metal objects.

In painting, the term patina means “aging” or “shimmering.” A variety of chemicals, from synthetic and organic substances, are added to metals in order to create the patina effect. The surfaces may be etched, painted, varnished, ground flat, coated with gold, silver, copper, bronze, or even metal salts.

There are two types of patina–chemical and physical. Chemical patina is usually achieved by applying certain chemicals to metals. Organic patina is achieved by forming metals from their salts or organic solvents. Both types of patina occur naturally with certain metals, such as copper, nickel, zinc, aluminum, tin, and magnesium. Some other metals, such as titanium, do not have sufficient fatty acids to support a chemical patina and thus cannot be etched, painted, or varnished.

The physical patina occurs when the surface of a metal is scratched or worn. The scratches and wears occur without damaging the metal in any way. Examples of such chemicals include oil, waxes, and other substances that naturally condition the surface of metals. After the metal has an adequate amount of these substances applied, the surface can be etched, painted, or varnished. After this process, it is ready to use.

Patina and copper are similar in many ways, especially in terms of appearance. Copper and bronze patinas are formed during the chemical process, but the patina formed on copper is more refined and purer than that formed on bronze. Gold patinas are usually white. Brass patinas can be found in a rainbow of colors. Copper, gold, and brass all have the ability to be formed into beautiful patterns. Patina can also be caused by wearing down of the fine metal parts of a component, such as a small brass screw that has been repeatedly exposed to moisture.

The main difference between patina and surface corrosion is that patina is formed over a period of time, whereas surface corrosion happens quickly. For instance, if you drop a container of lemon juice on your counter, the lemon juice will begin to Leach from the surface, starting a chemical reaction that produces surface corrosion. But, because of the quick rate at which this chemical reaction occurs, the end product is not very smooth – it’s more lumpy. It also has tiny little nooks and crannies in it that will cause future corrosion and damage to the surface.

There are several other different types of chemicals that can form a green patina over time, including: blue-green, red-brown, yellow-green, and green-yellow. Blue-green refers to the mottling of the metal that can occur if an agent like iron or mercury reacts with the metal. Red-brown is a reddish brown patina that can occur if the metal has an oxidation point, such as iron. Yellow-green is the most common variety and is formed when the metal is exposed to oxygen. Green-yellow has a greenish hue to it, and is formed from substances that react with the metal, such as chlorine. And, green-yellow patina is the most difficult to remove and therefore is the most prized type of patina.

Another type of patina recipe involves using potassium hydroxide in the presence of water. Potassium nitrate is commonly used as an industrial cleaner because it is soluble in water and therefore less likely to form a hard film on the surface of an alloy. The properties of the chemical make it ideal for removing tough grease and oil stains on metal surfaces, but it can also be very harmful if ingested. If ingested, large amounts of potassium nitrate can result in neurological problems – this is particularly true if swallowed by children. For this reason, this chemical should only be used as a topical solution and should not be ingested.

City Chemical is a producer of chemicals and some of them are: 1,4-Naphthoquinone, 130-15-4, Triolein, 122-32-7, Antimony Trioxide, 1309-64-4, Silver Nitrate, 7761-88-8, Aluminum Fluoride, 7784-18-1, Ammonium Iodide, 12027-06-4, Cupric Oxide, 1317-38-0, Humic Acid, 1415-93-6, Triethylsilane, 617-86-7, Zinc Chromate, 13530-65-9.

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