Alabaster repair and care
Alabaster, a beautiful, translucent and thin (fine grain) stone, has been valued for hundreds of years. It is similar to marble, and the two stones confuse. Alabaster was extracted from quarries for many years in Italy and Egypt. But the creations of ancient Egypt and Rome calls were actually alabaster marble. Adding confusion, the term “Onyx” has been applied to marble, alabaster and onyx true, which is a form of quartz.
Soft, alabaster translucence reminiscent of a highly polished marble or onyx also with the same ending. The color and grain variety of views on various types of alabaster, is also reminiscent of marble or white color. However, alabaster has several different properties that can lead to problems if incorrectly cleans, stores, displays or manipulates. Here we describe the properties of objects in alabaster and some tips on how to care.
Images about alabaster projects in our Arastone projects page.
What is alabaster?
While usually contains a variety of minerals, alabaster actually has a predominant material. Alabaster is the form of fine-grained mineral Gypsum (calcium sulfate). Marble, especially white marble is mainly calcite (calcium carbonate). Both are metamorphic rocks, geologically formed under high pressure and temperature. Alabaster is also sometimes confused with steatite, other soft stone and can be easily polished.
This basic difference between the chemical composition of alabaster and marble realize their very different properties. Alabaster is water soluble while marble no. Alabaster is softer than marble, but it can be polished to make the surface look almost perceptually hard as glass. It is a very attractive property for artists and craftsmen who perform delicate and fine, translucent walls sculpted pieces such as vases, lamps and lampshades, the easily worked material. However, alabaster is extremely fragile and easily suffers marks. It can be marked with a nail.
More information here: what is the alabaster.
Identifying alabaster objects
Most of Alabaster objects are indoors, because of its vulnerability to moisture. A variety of items can be found in museums and antique collections, from mundane to exotic objects: knobs, letter openers, ashtrays, bookends, chess pieces, busts, sculptures, jewelry items, furniture ornaments, to name a few. Medieval alabaster reliefs found in collections in North America, as have religious items such as alabaster altarpieces and figures of Spanish, French, English and Italian. These parts are usually delicately carved, polished smoothly and are always painted and decorated with gold. In Europe, Asia and North America, a long tradition of creating figurines and small alabaster sculptures for collectors and tourists still remains. Decorative household objects such as boxes, lamps, lampshades, are also common. Some heads and limbs of antique dolls were painted alabaster, alabaster and is also embedded in furniture and other objects. In addition to these objects and creations, some alabaster sculptures and crafts incorporated with other materials, including various types of stone, wood or metal. For example, some contemporary artists of Indigenous communities in Latin used as a means of alabaster sculptures always embedded or attached components.
Alabaster identification is difficult without a destructive test. It is understood that some tests such as resistance to tearing or diluted hydrochloric acid is not acceptable for historical and art pieces. The surface coatings can complicate the identification of alabaster. You can be tested under ultraviolet light to make surface layers endings but the alabaster not react to that light. If the surface is highly translucent and crystal grains are not, it is best to assume that is alabaster and take appropriate measures to protect and preserve it.
Deterioration and damage
Alabaster, yet still fragile soluble in water, is prone to break or deteriorate if handled or stored improperly. Its surface is marked and easily bruised. But you can do more damage with cleaning attempts with good intentions. The extremely fine grain of alabaster makes it less porous than some marbles, but still permeable to water and soluble salts. It is also easily spotted. Dirt is added to the surface. The land is very difficult to clean especially if the alabaster reacted with moisture to form a re-precipitation of gypsum in the soft surface. Gypsum has a microscopic form of fixed cutting blades which dirt crystals in place. This property makes it much more difficult to clean than alabaster marble.
Air pollutants can cause discoloration in alabaster, usually seen as yellow markings. Also these yellow markings can be caused by cleaning products. Strong acids and alkalis can cause discoloration, sometimes reacting with ferrous minerals containing alabaster.
In the past, routine cleaning of alabaster objects, including the use of a fine abrasive surface for regrinding after an aggressive removal, then apply wax or oil to help retake the translucency and color. In addition to the obvious damage caused by these cleaning practices, these wax or oil endings always had problems over time. Oils darken and become opaque, always followed by a yellowish or brown appearance. Waxes, especially after repeated applications over time, accumulate dirt, which may be embedded in the stone.
Some alabaster sculptures, reliefs, and other decorative objects have layers of paint or gold applied. These layers are extremely vulnerable to environmental conditions and rough handling. Many painted surfaces have been lost due to the extreme cleanliness or poorly made.
The damage always occurs when alabaster is combined with other materials in the construction of the object. For example, a metal or wood frame can move alabaster producing pressure on the break. Old restorations always made with metal staples embedded in small holes in alabaster. When, due to changes in temperatures, these metal parts expand and may cause breakage. Other arrangements can cause damage, such as plaster, adhesives shrink and become brittle over time.
Although an object of alabaster apparent need cleaning, consider accepting a less pristine condition it can be associated with a “patina” of age, rather than risk the delicate surface. It is a good idea to prevent dust buildup, as this can attract moisture to the surface. Clean the surface with a cloth can statically loaded to it which will attract more dust; Instead, use a soft bristle brush with plastic tape around metal parts to prevent scratching. If a more complex action is required consult a restaurateur.
Unless you are sure that the surface has a protective layer of wax, resist the temptation to use diluted detergent to remove dirt or stains. Even pouring small amounts can lead to a permanent stain. Let dry happened and call a restorer.
If a piece of alabaster breaks or bankruptcy, gather the pieces and wrap them with something soft like a cotton cloth. Do not touch the delicate edges of the cracks. Only a restorer should perform repairs. Resist the temptation to use adhesives. The broken edges are delicate and using improper adhesive can result in irreparable damage or stains worse.
Always wear gloves when handling pieces of alabaster. The oil from your fingers easily penetrate the surface and can eventually cause stains or attract dirt. Remove any metallic element of the hands to prevent scratching the surface. Before handling an object, be sure to understand how their components are assembled and move one hand at a time.
The alabaster should be stored in a stable environment, as it will absorb and expel water vapor in extreme humidity. Avoid any contact with moisture. Wrap the pieces individually in nonabrasive cotton cloth and store in a container or shelf stable.
Large objects must be protected from dust; They can be covered with polyethylene keeping the same away from the object surface by a carrier such as polyethylene foam. Allow ventilation to avoid condensation, for the same reason it is advisable not hermetically seal the pieces.
Alabaster minimize exposure to heat lamps, reduce the power of the light source, use small lamps or minimize the time that the light comes on periodically. Although generally not affect the light stability of color Alabaster, can affect surface coatings have been applied. Secure mobile objects that may contact and cause damage alabaster well. Do not use any glue to do, unless you have tested the reaction of both surfaces with sufficient time.
By John Griswold
Griswold Conservation Associates , LLC
Images about alabaster projects in our Arastone Projects page.