What is acid etching on marble?

by 31 August 01, 2013

Before we can answer this question we must know the characteristics of marbles, i.e. marble, limestone and travertine. It's easier to class these stones as marbles as they are all calcite containing natural stones making them soft and sensitive. Hard stones like granite are extremely strong and durable and are mostly scratch resistent in normal circumstances. Marbles can be damaged by acids, abrasive and corrosive products or perhaps a product that is not designed for use on natural stone. "Marble is a non-foliated metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite. Geologists use the term "marble" to refer to metamorphosed limestone; however, stonemasons use the term more broadly to encompass unmetamorphosed limestone." Because of the calcite content of marbles they are soft and sensitive with a chalky feel when in their raw state. When an acidic product comes in contact with the surface of the marble the acid dissolves the calcite within the marble causing a dull area. This is called acid etching. This dull patch or acid etch is damage to the composition of the stone surface and must be mechanically re-polished or re-honed to regain the original polished or honed finish. Acid etching is not a stain but damage to the composition of the stone surface. Marbles show signs of use over time via foot traffic, general use, external environments or incorrect cleaning procedures. "Acid Attack. Acid-soluble stone materials such as the calcite in marble, limestone and travertine, as well as the internal cement that binds the resistant grains in sandstone, react with acidic solutions on contact, or on absorbing acid-forming gases in polluted air, such as oxides of sulfur or nitrogen. Acid erodes the stone, leaving dull marks on polished surfaces. In time it may cause deep pitting, eventually totally obliterating the forms of statues, memorials and other sculptures. Even mild household acids, including cola, wine, vinegar, lemon juice and milk, can damage vulnerable types of stone. The milder the acid, the longer it takes to etch calcite-based stone; stronger acids can cause dramatic damage in seconds." Acid etching is different from a stain as a stain can be cleaned out of the marble with the use of a the correct cleaning product. Lithofin have a number of stone specific cleaning products to remove all kinds of dirt's and stains from natural stone including marbles. i.e. to provide marble with a thorough and intensive clean use Lithofin MN Power-Clean, to remove oil use Lithofin Oil-Ex or for general cleaning and mainteance  of stone tops use Lithofin MN Easy-Clean spray. Most stone tops, floors, bathroom and external areas are sealed with an impregnating sealer upon installation which does not alter the appearance of the stone, allows vapour transmission (breathability) and prevents the penetration of water, oil, grease and general dirt's. Because the surface of the stone is not protected and remains exposed acid etching can still occur. It's a very important to note that even if marbles are sealed with an impregnating sealer acid-etching will still occur. Please remember that marbles will create their own patina over time through general wear and use. The Europeans and Americans appreciate this allowing their stone to be used like any other surface wanting the marble to create it's own personal characteristics and warmth. They do not have the stone re-polished when worn. However, if you do want to have you stone periodically re-polished then the Stone Doctor www.stonedoctor.com.au can perform this service.

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