Glossary

A   B   C   D   E   F   G   H   I   J   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z

A

acetone
A colorless volatile organic liquid used as a solvent for synthetic adhesive or consolidant resins. Also used as a dewatering or degreasing agent.

acetone-rosin treatment
A stabilization treatment for archaeological waterlogged wood, involving dehydration with acetone, followed by impregnation with an acetone solution of natural rosin, sometimes heated. No longer commonly used because of health and safety reasons, and questions about the long-term degradation of the rosin.

acid-free
A designation for archival materials with a natural or manufactured pH between 6 and 8.

acid-free board
Chemically treated cardboard which will not itself degrade or affect archaeological objects placed in contact with it. It is used to construct boxes and supports for artifacts. Acid vapors from ordinary paper and card can cause tarnishing and corrosion on metals, especially those containing silver and lead.

adhesive
A generic term for materials used to bond pieces of objects together. These can be either natural glues, or synthetic resins. Adhesives chosen for use on cultural materials have undergone testing to ensure their long-term stability. Many adhesives are not suitable for use on archaeological and historical materials

air abrasive cleaning
A method of revealing the surface detail on artifacts beneath layers of corrosion and concretion by shot-blasting on a miniature scale, using fine abrasive powders and compressed air, and with the aid of a low-power microscope.

anaerobic
A synonym for anoxic: an environment with no oxygen content. Often used in the context of waterlogged burial environments.

anoxic
A synonym for anaerobic: an environment with no oxygen content. Particularly used in the context of storage environments.

archival
An industry designation (but not a standardized definition) for packing or labeling materials that are inherently stable in long-term storage, and will not contribute to the degradation of the objects stored within.

archival boxes
Containers made of acid-free card or other inert material which will not, itself, have a harmful effect on artifacts stored in them.

B

benzotriazole (BTA)
A corrosion inhibitor chemical for copper alloys. It bonds with theexposed surface to provide a passivating layer and prevent reactions with oxygen and moisture. Commonly used to stabilize actively corroding copper alloys after some or all of the corrosion products have been removed.

block-lifting
A method for lifting and removing a large or fragile object from archaeological excavations by surrounding it with rigid foam or some other supporting material. The block will often incorporate some of the surrounding soil, which gives extra support to the object.

bronze disease
Not a disease, but a rapid and destructive type of corrosion that produces bright green spots and patches on copper alloy objects, particularly if they are kept in damp conditions. The corrosion is caused primarily by the reactions of unstable cuprous chloride.

C

CAT scan
Computed Axial Tomography: A digitized image of the interior structure of a 3-D object, produced by passing the object through a body scanner, like those used in hospitals.

chelating agent
A family of chemical reagents (e.g., EDTA) that actively grab and hold onto metal ions dissolved in solution, preventing them from re-reacting or re-depositing on the artifact surface. In extreme cases, chelating agents can aggressively strip and etch exposed metal surfaces.

coating
A resin or other material applied to the surface of an object to protect it from its environment.

consolidant
A dilute solution of a resin (normally a synthetic polymer) in a solvent, used to impregnate a fragile object in order to strengthen its structure.

copper alloy
An alloy is a mixture of metals. Copper alloy is a generic term for those alloys made up of copper blended with tin (bronze), zinc (brass) or lead, or other metals.

corrosion products
The compounds formed due to reactions between a metal and its environment. They may form a disfiguring film or crust, or may form a protective film or crust, as in the case of a patina.

D

dehydration
The removal of water from an object, either through the process of natural drying or by replacement with an organic solvent such as acetone.

de-ionized water
Water that has been purified by being passed through an activated resin to remove dissolved salts and other impurities.

dendrochronology
Method of dating wooden objects by comparison of annual growth rings.

desiccant
A chemical drying agent, typically used to create a low relative humidity environment.

E

EDTA (ethylene diamine tetraacetic acid)
A chelating agent commonly used to remove calcium deposits from fragile surfaces, or to remove tough adherent metal corrosion films or stains from organic materials.

electrophoresis
A method for removing soluble charged ions (generally mineral salts) from objects by suspending them in an electrolyte between negative and positive charged poles. The different ionic species will be attracted out of the object to the appropriately charged pole.

electrolysis
A method of desalinating metal objects. May also be used for cleaning. One form of electrolysis, electrolytic reduction, can reduce corrosion minerals to either a more stable state, or back to a metallic state.

environmental archaeology
A general term which includes the study of ancient plants, animals, insects and soils.

epoxy resin
A thermosetting polymer that cures (polymerizes and crosslinks) when mixed with a catalyzing agent or “hardener.” Once set, the resultant resin is no longer soluble or reversible.

ethanol (ethyl alcohol)
The most common form of alcohol, used for dewatering, degreasing, or as a solvent for resins. Mixed with the more toxic methanol (methyl alcohol), it is marketed as Industrial Methylated Spirits (IMS) or Denatured Alcohol.

F

freeze-drying
A safe and widely used method of drying waterlogged archaeological organic materials without structural collapse, involving freezing the object, then sublimating the ice under vacuum. The object is usually first treated with a “cryoprotectant” to protect it from freezing-stresses.

Fourier Transform Infrared Spectroscopy (FTIR)
An analytical technique which identifies molecules and compounds by the absorption of specific wave-lengths of infra-red radiation. Commonly used to identify organic materials.

G

glue
Commonly, but incorrectly, used as a synonym for adhesive. The term glue should only be used for natural adhesives such as animal skin glues.

gum
Commonly used to refer to adhesives derived from natural plant resins.

H

I

incralac
A proprietary name for a coating developed for copper-alloy based materials that incorporates a synthetic resin base, BTA corrosion inhibitor, and a mixture of solvents.

investigative conservation
The process of uncovering information about an object through actions such as examination under a microscope, radiography and corrosion removal.

iron tannate
A dark-colored layer on the surface of iron objects produced deliberately as part of a conservation treatment with tannic acid to provide a measure of protection against corrosion.

J

K

L

M

mechanical cleaning
The selective removal of dirt, corrosion and concretion from the surface of artifacts using hand-held tools (such as a scalpel) or small power tools (such as the airbrasive).

mineral spirits
Generic name for a family of solvents derived from petroleum, commonly used in paints, paint thinner, varnishes, and some synthetic resins.

N

non-ionic
A non-reactive liquid that is completely removable after use. The term is normally applied in conservation to a soap or detergent.

O

off-gassing
The emission of a gas that may contain acids, sulfur or other harmful substances. Off-gassing may occur from artifacts themselves, storage materials, exhibit materials,materials such as paints and carpeting, or from the artifacts themselves.

organic
A term meaning related to or deriving from living plants and animals. Organic materials include wood, leather, bone and textile. Some organic compounds, such as plastics, can also be produced synthetically.

oxygen-free atmosphere
A space or container that has had the oxygen removed, often by allowing a stream of nitrogen to replace all the air or by placing oxygen scavengers in a well sealed space. Synonym: anoxic.

oxygen scavenger
A material that absorbs all the oxygen within a sealed container in order to create an oxygen-free environment for storage and long-term preservation.

P

passive conservation
Stabilizing an artifact by controlling its environment, rather than altering its fabric or adding foreign materials.

patina
A type of corrosion film on metals, especially bronze, that is often admired for its beauty and revered as a product of age. The word is sometimes used to describe the aged surface of other materials as well, such as glass and ivory.

polyester resin
A liquid resin which sets solid through the addition of a catalyst, and is non-reversible. Often used in conservation to form moulds and supports, usually in combination with fiberglass.

polyethylene glycol (PEG)
A water-soluble synthetic polymer, available in a range of molecular weights from liquid to solid, widely used for the stabilization of waterlogged organic archaeological material, often in conjunction with freeze-drying.

polyurethane
A synthetic resin used to make coatings and foams. Most commercial formulations are not stable in the long-term, and are also irreversible, making them difficult to remove.

poly-vinyl acetate (PVA)
A common synthetic resin, used as an adhesive or consolidant. Can be dissolved in organic solvents, or emulsified in water.

poly-vinyl alchohol (PVAl or PVOH)
A synthetic resin, no longer used in conservation, sometimes confused with polyvinyl acetate.

poly-vinyl chloride (PVC)
A common industrial plastic, not used in conservation or archival situations because it releases hydrochloric acid as it breaks down.

pseudomorph
The replication of an organic material, formed by the replacement of organic components by inorganic salts. Petrified wood is a pseudomorph. Wood, leather, bone, and other organic materials, in contact with corroding metal can also form pseudomorphs.

Q

R

relative humidity
A measure of the amount of water contained within a fixed volume of air, expressed as a percentage of the maximum amount of water which a particular volume of air can hold at a particular temperature.

replacement corrosion
The corrosion that forms on and below the original surface of a metal object, effectively replacing these parts and often replicating surface detail.

resin
A generic term covering synthetic or natural polymers, often soluble in water or organic solvents. Resins are used as adhesives, coatings, and consolidants.

reversibility
The concept that a conservation treatment or added material can be reversed, removed, or otherwise undone.

S

Scanning Electron Microscopy (SEM)
A technique for the visual inspection of objects at very high magnification that uses electrons instead of photons for imaging purposes.

silica gel
A crystalline material capable of absorbing large quantities of moisture from the air. Used widely as an aid to controlled storage of archaeological material, either to keep material dry or to maintain it at a pre-determined relative humidity.

stabilization treatment
To render an object physically sound and/or chemically inactive through conservation measures, to ensure the long-term survival of an artifact.

stripping
Any cleaning method (especially chemical) that removes all extraneous surface materials, revealing the substrate (which may, however, be disfigured by corrosion or decay).

synthetic resins
Man-made polymers manufactured to have particular physical and chemical properties to suit them to specific applications. Used widely as adhesives and consolidants in archaeological conservation.

T

tannins
Complex organic compounds found naturally in the soil and in certain tree barks. Used both in the past and in the present to turn hides into leather.

tannic acid
A pale brown powder which, in solution, is sometimes used in conservation of iron to form a protective black surface film.

toluene
A strong, toxic solvent, often found in commercial paints and varnishes.

U

ultrasonic cleaning

Passing high-frequency sound waves from an electrical unit through a suitable cleaning solution causes high-speed agitation which speeds up the chemical removal of dirt, corrosion or concretion from the surface of an artifact.

V

W

waterlogged
Saturated with water to the exclusion of all air. Waterlogged archaeological deposits are often anoxic (no oxygen) and therefore protect metals and some organic materials. Waterlogged organic artifacts (e.g. made of wood) are normally heavy, fragile and liable to physical damage through uncontrolled drying and poor handling unless given first-aid conservation treatment upon discovery.

X

Y

Z

xylene
A strong toxic solvent often found in commercial paints and varnishes.

X-radiography
A non-destructive imaging technique used widely in archaeology. It uses X-rays to produce images either digitally or on film which show, for example, the details beneath the surface of badly corroded metalwork.

X-Ray Fluorescence (XRF) analysis
A non-destructive technique used in archaeological research to identify the elemental composition of a material. Used particularly for the analysis of metals.

X-Ray Diffraction (XRD) analysis
An analytical technique that identifies crystalline materials by passing X-rays through a powdered sample, and measure the resulting angle of diffraction.

Copyright © 2006 Colleen Brady, Molly Gleeson, Melba Myers, Claire Peachey, Betty Seifert, Howard Wellman, Emily Williams, Lisa Young. All rights reserved. Commercial use or publication of text and graphic images is prohibited. Authors reserve the right to update this information as appropriate.