The  NATURAL HISTORY ART GALLERY

A Collectors guide to  conservation, care and handling OF WORKS OF ART AND DOCUMENTS

A 19^th century chromolithograph heightened with hand water coloring has dark yellow margins indicating   an acid content.  The original paper has become acidic through prolonged contact with acidic framing materials.  Stains have been reduced by washing the paper on a vacuum table and the paper deacidified with a non-aqueous alkaline solution.

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glossary

Acid: A substance able to donate protons to other substances.

Acid-free: A paper product having a pH level of 7 or higher.

Acidic:  In paper, an unstable state whereby the molecular structure of the paper breaks down, causing discoloration and weakening of the sheet.

Alkaline Buffer: An additive used in paper-making processes and conservation treatments that will raise the pH level.

Alum:  Aluminum sulfate; employed to precipitate rosin sizing in paper.

Aqueous Treatment:  Any restoration procedure that utilizes water.

Archival:  An archival material should have neutral or slightly alkaline pH; it should also have good aging properties.

Cellulose: A substance constituting the chief part of the cell walls of plant material, trees and paper.

Chemical Suction Vacuum:  A device used for localized chemical and aqueous treatments to paper.

Covalent Bond:  A chemical bond formed by sharing of one or more electrons between atoms; the type of molecular structure that forms cellulose in paper fibers.

Deacidify:  To chemically stabilize acidic paper; can be either aqueous or non-aqueous treatment.

Dry Peel:  A restoration technique that is manual (non-aqueous and non-chemical) and employed to reduce or remove a mount material.

Embrittlement:  A fragile condition that results from dehydration and prolonged acidic degradation.

Expansion:  The result of change in the dimension of a sheet of paper due to excess humidity; more pronounced across the grain with it.

Fiber Fill:  Utilizing paper pulp to complete losses in a sheet of paper.

Fillet:  A spacer device placed between the glazing and the mount in a frame which prohibits the glazing material from coming in contact with artwork.

Flattening:  A restoration procedure involving controlled humidification and controlled drying under pressure.

Foxing: A type of stain in paper resulting from mold growth.

 Fragmenting:  A sheet of paper with portions broken off or detached.

Gelatin:  One of many sizings that may be used to make papers less liable to bleed; a glutinous material obtained from animal tissues through continued boiling.

Heat-Set Tissue:  Any one of a variety of heat-reactive tissues used as an adhesive material.

Hinge:  In framing, a folding or hanging device used to attach artwork to a mount while allowing limited movement to occur.

Hydration:  In restoration, the process of introducing moisture to an embrittled, dehydrated sheet.

Hygroexpansivity:  Expansion or contraction of paper due to changing conditions of humidity.

Interrupted Fiber:  In a fold, when the fiber has ruptured or torn; the paper surface is no longer continuous.

Leaf Casting:  A process employing cold suction to complete voids with pulp.Lingnin:  A complex polymer; the chief non-carbohydrate constituent of wood that binds to cellulose fibers and strengthens the cell walls.

Mulberry Tissue:  a long fibered, unsized, acid-free Japanese paper which is used as a support mechanism for weakened sheets or tears.

Paper Conservator:  An individual professionally trained to preserve and restore paper.

Paper Inlay: A solid piece of paper grafted to a sheet to complete a void.

pH Value:  A method of measuring acidity or alkalinity, numerically equivalent to 7 for neutral solutions, increasing with increased alkalinity and decreasing with increased acidity.  The pH scale commonly in use ranges from 0014. p(otential of) H(ydrogen).

Pulp:  The fibrous substance resulting from the pulping process in papermaking.

Rabbet:  The “l” shaped cutout frame that forms the lip.  The part that holds the picture and other framing materials.

Reversibility:  A material possessing the property that allows the material to be completely removed without damaging the original.

Rosin:  A substance derived from distilled gum turpentine; used as a sizing ingredient in paper.

Sizing:  A substance added to paper to create a degree of water resistence.

Substrate:  The primary layer of material; can relate to a mount substance or the base material upon which a work of art is executed.

Surface Clean:  Any one of various dry, non abrasive methods of removing surface dirt, soot or grime from a sheet of paper.

Thymol Vapor Treatment:  Thymol is a white crystalline aromatic compound derived from thyme oil or made synthetically and employed in a gaseous state fungicide to kill mold.

Tidemark:  A stain; a deposit which occurs at the point where water entered a sheet of paper and stopped.

Ultraviolet Light: Primarily invisible light, ranging from the X-Ray region, about 4 nanometers wavelength you just beyond the violet in the visible spectrum, about 380 nanometers.

Van Der Walls Force: A weak attractive force between atoms or non-polar molecules caused by a temporary change in dipole moment arising from a brief shift of orbital electrons to one side of one atom or molecules.  One of the phenomena that bonds fibers together to form a sheet of paper.

Varnish:  Any one of the various transparent coatings, synthetic or organic, used as a final layer on the artwork surface.

Void:  A gap pr area of paper missing from the original.

            Wet Peel:   A method of reducing or removing a mount material involving aqueous treatment, but avoiding immersion in a water bath.

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