Caring and Cleaning of Antique Stonework

Stonework seems eternal to human eyes and our short life span but it is not. Stone statuary must contend with forces of nature, wind and rain, it must withstand frost and thawing. Although it seems unlikely marble can be destroyed by fungus; it takes awhile but it happens. Not to mention lichen, swinging tree branches, mildew, and bird droppings.

Even mighty igneous granite is subject to impurities in the air that can discolor and even dissolve it. Some of these occur naturally and others are the result of industrial pollution, fireplaces, and other works of man. It is a common problem with very old stone pieces to have had candle wax spilt on them long ago and has been stained.

Unlike modern candles, those made before the 20th century were made from organic materials. Usually derived from animals, candles contained oils in the form of fat that will stain most materials including stonework.

Atmospheres with high concentrations of either sulphur or salts can do terrible things to stonework. A visit to the magnificent cemeteries of New Orleans will plainly show what years of salty air and petrol-chemical production can do to a head stone or statute.

The antique stonework collector must deal with far dirtier pieces and a wider variety of cleaning methods than those of other more delicate collectibles such as fine china or glassware. The good news is, generally speaking, it's harder for the beginner to do any great damage.

The Practical Bit

You have brought home a new stonework garden lamp and need to know what to do with it. First thing is, give the poor trooper a break and bring it indoors. It is often tempting leave antique stonework in its natural environment and bring beauty to a favorite garden spot or brighten the patio. Resist, remember than damage that just being outside can do and find a place in a gentler atmosphere.

Let’s look at the simplest cleaning scenario first. Very hard igneous rock such as basalt or granite can take a lot of abuse. Start out with a brush, a good stiff one but in all but the most extreme cases avoid wire bristled brushes. A bucket of warm, soapy water and a lack of a fear of getting wet is all a collector needs to get years of soot, lichen growth, and bird droppings.

It is simply amazing how much soot and general grime a piece of stonework can accumulate over the centuries. If the layers of soot and the like can’t be overcome with simple detergent you’ll have to call in bigger guns.

Usually this means a more caustic household cleaner or abrasive powder of the type used to clean sinks and bathroom tile. Try to avoid ones with unnecessary added color as it could stain your stonework. Using a scrub brush apply the powder in small amounts working up to the amount needed to do a thorough job. Once your finished be sure to rinse the piece thoroughly with clean water and dry with a towel.

The most common acid-based cleaner, both sulphamic and phosphoric will erode softer stone and should normally be avoided. However, sometimes with particularly grimy pieces it is simply impossible to avoid. When using acidic bases that require mixing follow the manufactures directions exactly. This cannot be over-stressed; many acids can be very dangerous.

Before resorting to any acidic cleaning agent make sure the piece is not polished. Acidic compounds can dissolve finishes and polishes. It is always a good idea to select a test area on a normally unseen spot before applying any chemical to an antique of any kind.

An old restoring guide I read recently suggests that in this case to use a mixture of the dangerous benzene and the illegal carbon tetrachloride. It's a wonder anyone survived preparing such a concoction more less used it on an antique.

Really the best thing you can do is contact a local stone company and ask advice about a modern stone cleaning agent. They will almost certainly carry one or two and can offer advice. Just remember to tell them the type of stone youĂ­re working with to avoid overly acid cleaners on softer stones such as lime or sandstone.

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Silas Finch is a freelance writer and regular contributor to Collectible Antiques Etc. He can be reached at Content and Solutions.

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