GLOSSARY

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B

backboard

The part of a mat made from a solid piece of mat board, which functions as a protective support for works of art on paper. This term is sometimes confused with a backing board, which serves a different function. See also Mounts, mats.

backing board

A protective sheet of material attached to the verso of a frame, or sometimes directly to the stretcher, to isolate the back of the support from the environment.

baryta coating

A coating made from the mineral, barium sulphate. It is opaque and white. In photographs, the baryta layer is made of barium oxide with a binder to hold it together, or barium sulhpate suspended in gelatine. It is applied to photographic printing papers under the emulsion layer to mask the colour and texture of the paper and ensure a smooth image.

bequest

The acquisition of items after the death of an individual as a result of a direction in that individual's will.

bleaching

The cosmetic whitening or reduction of coloured substances by the chemical action of an oxidising or reducing agent. The process is likely to weaken paper or textiles and is rarely a recommended conservation treatment.

blind tooling

Book decoration where a pattern or lines are pressed into the leather without the use of gold leaf, ink or coloured foils. See also Gold tooling.

blistering

Bubbling between layers of paint or between paint and the surface it is covering, often caused by heat.

bloom

a) On metals, a loose, flower-like corrosion product which forms when certain metals are exposed to a moist environment.

b) On paintings, a cloudy appearance on the varnish of the painting, probably caused by the presence of moisture on the surface of the paint or in the varnish itself at the time of original varnishing.

c) On other organic objects, a term used to describe the visible appearance of active mould spores.

blunder trap

See Insect trap.

bone folder

A flat piece of bone or plastic with rounded corners and edges. It is used to score and fold paper and light card when making storage folders.

book shoe

A type of hand-made book support, similar in appearance to an open-topped slipcase. It is designed to protect the text block of a book as well as its covers. Book shoes are used for large or thick books whose text blocks could sag away from the spine if shelved vertically for long periods. A raised platform on the base, formed to fit the text block, provides the lift required to keep the text block correctly aligned.

bookcloth

A cloth used in bookbinding, to cover and protect text blocks. The cloths are often coloured and treated to improve water-resistant and durability. They were traditionally made of a woven fabric like cotton or calico but, increasingly, polymer-coated cloths are being used.

brightness

See Illuminance.

brittle/brittleness

A property or condition of a material, such as paper, board and adhesives, that causes it to break when it is deformed by bending. Paper is said to be brittle when a corner will not withstand two complete folds.

bronze disease

A non-protective corrosion of copper and bronze objects, caused by the production of copper chlorides which break down the normally protective surface patinas. Light blue-green blisters form on the surface. When they are touched, they crumble and fall away leaving a pitted surface. The corrosion is cyclic, setting up reactive and destructive corrosion cells on the surface of the metal.

buckling

Distortion caused by shrinkage or compression.

buddy system

Using an experienced person to work closely with a new staff member, showing them how to do things on-the-job.

buffered

See Alkaline buffering.