Marble: Characteristics, uses and problems.
- Oil/grease stains: The appearance of grease/oil stains will usually consist of a darkening of the stone at the area of contact.
- Dyes and inks: The staining can be any colour depending on the type and source of the dye. The liquid containing the colouration may be absorbed into the stone and during the normal process of evaporation, the colouring pigment is deposited within the stone.
- Organic stains: Organic stains are caused by direct contact with decomposing organic matter, such as leaves, bird or animal droppings, flowers, tea or coffee.
- Metallic stains: Two major categories of metallic staining are based on either iron or copper. A common source is the water wash, or run-off, from adjacent metallic elements, especially bronze. Rust stains, these stains are reddish-orange and are caused by the oxidation (rusting) of iron. Copper stains are coursed from water run-off from bronze. The stains can range in colour from a light green to a dark brown.
- General dirt, soot and pollution: The visual appearance is usually a dulling or greying effect which mutes or obscures the original colour and gloss.
Chipping:
The separation of small pieces or larger fragments of marble, frequently at the corners, edges or mortar joints is known as chipping. These fractures are generally caused by deterioration and re-pointing, especially due to the use of too hard a pointing mortar, or by accident or vandalism. Repairs include detachment repairs, patching and splicing.
Cracking:
This condition is manifested by the appearance of narrow fissures ranging from less than 1/16 to 1/2 inch wide or more in the stone. It results from a variety of causes, such as structural overloading due to settlement, the use of too hard a mortar mix or a flaw in the material. Minor cracking may be no problem, in and of itself, but it can be an indication of structural problems and the cracks can be a source of entry of water into the interior of the stone, promoting salt migration. Repairs include patching and replacement.
Efflorescence:
The appearance of a whitish deposit locally or uniformly over the surface may be efflorescence, the surface deposition of soluble salts. There are numerous sources for the soluble salts which create the hazy appearance; salts can come from mortar, improper cleaning agents, rising damp, de-icing salts, chemical landscaping treatments, air pollution or from improper chemical cleaning, i.e. too strong a chemical cleaner or inadequate rinsing.
Flaking:
This is an early stage of peeling, exfoliation, delamination or spalling evidenced by the detachment of small flat thin pieces of the outer layers of stone from a larger piece of stone. Flaking is usually caused by capillary moisture or freeze-thaw cycles which occur within the masonry. The problem can also occur due to sub-florescence, so that if flaking occurs, the area should be examined to determine if salt crystallization is occurring in the flaked areas.
Peeling:
Peeling is flaking away of the surface from the substrate in strips or layers. It may result from the improper application of masonry coatings which result in failure of the coating and/or stone surface. It may also result from a defect in the stone, or from
weathering. Encrustation of the surface caused by chemical reactions with
environmental elements may also peel or flake along the bedding plane.
If you have discovered you have any of these problems and need to get them fixed, always consult a expert before proceeding with any cleaning or repairs. When using cleaning products always read the instructions to ensure that you are using the correct product and procedures for you problem.
