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The prevention and removal of surface dirt and corrosion products are the primary concerns of conservator-restorers when dealing with copper or copper-alloy objects. Perseus with the Head of Medusa , bronze, by Benvenuto Cellini, in the Loggia dei Lanzi gallery on the edge of the Piazza della Signoria in Florence; picture taken after the statue ...
Keeping your jewelry clean gives the gemstone(s) a good shiny appearance by removing dirt and grease (among others) from loosening them. Dirty jewelry may also cause skin irritation. [1] A professional cleaning may take anywhere from a few minutes to a few days depending on the circumstances.
Similar to many other bronze statues, the statue of Joseph of Portugal had an interventive conservation treatment. The conservation decision made to remove the patina most likely happened for two reasons. Firstly, it improves the visual impression of the statue; and secondly, the patina is a corrosive process slowly destroying the metal.
Unlike wear patina necessary in applications such as copper roofing, outdoor copper, bronze, and brass statues and fittings, chemical patina is considered a lot more uneven and undesirable. [2] Patina is the name given to tarnish on copper-based metals, while toning is a term for the type of tarnish which forms on coins.
Tarnish is a chemical reaction on the surface of metal (copper, brass, silver, etc.) and causes a layer of corrosion. In the case of silver tarnish, the silver combines with sulfur and forms silver sulfide (Ag 2 S), which is black. The original silver surface can be restored if the layer of silver sulfide is removed. [4]
The sesquicarbonate may remove copper from the artefact as it forms a complex ion with copper. Amateurs report that the patina may be stripped from the artefact but this is when the solution is boiled so that the carbonate rinse removes the chlorides in hours rather than the cool bath of long duration used by professional conservators. [2] [3]
Pickling is a metal surface treatment used to remove impurities, such as stains, inorganic contaminants, and rust or scale from ferrous metals, copper, precious metals and aluminium alloys. [1] A solution called pickle liquor, which usually contains acid, is used to remove the surface impurities.
Brown or black can be used as a base color for copper patina. If the amount of chlorides decreases the color will be more bluish-green, if carbonate decreases, more yellow-[27] Black for copper. Solution of sodium polysulfide 2.5%, items must be submerged in the solution after color developing, wash, dry and wax or varnish colored object. [28]