CCI Notes 10/11

Condition Reporting - Paintings. Part III: Glossary of Terms

Introduction

This Note explains the terminology used by conservators in condition reports. It will help museum personnel to write and maintain accurate condition report records for paintings. For detailed information on examination and condition reporting, refer to CCI Notes 10/6 and 10/7, Condition Reporting — Paintings, Parts I and II.

In this Note,

terms are listed alphabetically;
terms within a definition that are in bold letters are defined elsewhere in the Note;
Other term is a term that is often used as a synonym for the term being defined; and
See also refers to a term related to but not synonymous with the term being defined.

Abrasion

Damage to the surface of a painting, caused by friction. Some of the surface coating, paint, or paint and ground layers are lost because of scraping or rubbing.

Other terms: rub, scrape, wear

Accretion

A surface deposit of foreign material such as dried liquid residue, foodstuff, or fly specks. Accretion is an accidental addition to the painting's surface, not foreign material intentionally included by the artist.

Other terms: surface deposit

Artist's board

A general name for rigid painting supports such as millboard and academy board. These are primarily cardboard with surfaces prepared for oil painting. Also included in this category are canvas boards (i.e., cardboard with a primed canvas adhered to one side).

Other terms: secondary support

See also: Strainer, Stretcher, Support

Auxiliary support

The framework over which the painting canvas is stretched. It usually refers to a stretcher or a strainer.

Other terms: secondary support

See also: Stretcher, Strainer, Support

Backing board

A rigid board attached to the back of the auxiliary support or frame to protect the painting. (See Figure 1.)

Stitching the label.
Figure 1. Stitching the label with the accession number to the textile.

Edge-strip
Frame
Canvas
Bevelled edge of stretcher bar
Backing board

Bevel

The particular shape or cut of a stretcher or strainer bar with a top surface (adjacent to the canvas) that is planed or sanded to slope away from the back of the painting. The bevel prevents the canvas from touching the stretcher bar when ground and paint are being applied, and later prevents a stretcher mark from developing.
(See Figures 1 and 2.)

Other terms: chamfer

Binder

See Medium

Blanching

A local, opaque, whitish discoloration on the surface of a painting. Blanching occurs because of a loss of or an alteration in the binding medium in an oil film, or because of the partial dissolution of a varnish film.

Bleeding

When paint spreads or has been spread into adjacent areas of a painting.

Blister

A convex deformation of the ground, paint, or surface coating over an area of cleavage. Blisters are caused by excessive heating, poor adhesion between layers of a painting, moisture, or solvent action. A blister may be a form of blind cleavage.

Bloom

Areas of white, bluish white, or yellowish cloudiness in the varnish layer that is caused by contact with moisture or certain air pollutants. Unlike blanching, bloom affects only the varnish layer.

Buckling

Ridged distortions in the support or paint layers. Buckling is often associated with cracks, cleavage, and flaking.

Bulge

A local convex distortion involving the canvas and the paint and ground layers. Bulge is caused by sustained pressure to the back of the canvas, such as exerted by the presence of debris lodged between the stretcher and canvas or by an object leaning against the back of the canvas.

Canvas

A fabric painting support usually composed of linen, cotton, or hemp, and sometimes of jute (burlap) or ramie, or mixtures of these. (See Figure 1.)

Chalking

The powdering of a paint layer, caused by an insufficient amount of binding medium when originally applied or as a result of damage and deterioration.

Other term: powdering

Check

A partial split along or across the grain of a wood surface. In plywood or in wood that has dried too rapidly, checks may result from surface shrinkage.

Chip

Loss of a small amount of material as a result of mechanical action that caused it to break away.

Cleavage

A separation between layers of paint, between paint and ground, or between ground and support.

Blind cleavage

An invisible separation between the layers of paint, between the paint and ground, or between the ground and support. This may appear as a slight bulge in the paint surface.

Incipient cleavage

Separation between layers is beginning and further separation could occur.

Cockling

Wavy distortions or ripples in the support, usually associated with works of art on paper.

Crack

A break within one or more of the varnish, paint, or ground layers.

Drying cracks

Occur in the paint or varnish film during the drying process. Generally, these cracks have rounded or sloping edges and no cleavage.

Other terms: shrinkage cracks, traction cracks

Alligator cracks

A pattern of drying cracks that resemble alligator skin and that are associated with the different drying rates of the paint layers. The cracks have rounded edges and are often wide, exposing paint or ground layers below. Although frequently disfiguring, this paint condition is normally stable.

Other term: alligatoring

Mechanical cracks

Caused by movement or excessive stress within the various layers of a painting. Mechanical cracks have sharp edges. They may be distributed over the painting or may be restricted to one area associated with specific damage, such as a blow to the back or front of the painting. These cracks are often described by the pattern they create.

Cobweb cracks

A circular pattern of mechanical cracks caused by a blow to the painting.

Feather cracks

Mechanical cracks branching off from a centre line, resembling a feather. These cracks are caused by a line of contact against the back of the painting (e.g., a scratch or a glancing contact on the canvas with a hammer when keying out).

Spiral cracks

Mechanical cracks in the shape of a spiral. These are caused by forces within the painting.

Cradle

A system of wooden bars running horizontally and vertically across the back of a panel painting in a grid pattern. Cradles are meant to prevent warping without restricting the in-plane movement of the panel in response to changes in relative humidity.

Craquelure

A network of random cracks over the surface of a painting. Craquelure is caused by drying, by aging, or by changes in relative humidity.

Other term: crackle

Crazing

A network of fine cracks in the varnish, causing a loss of transparency. Crazing is associated with an aged and embrittled varnish layer.

Cupping

A condition where islands of paint, separated by cracks, develop concave centres with raised edges, like shallow cups.

Cut

A severing of fabric or paper caused by a sharp instrument, leaving clean edges.

Deformation

Change in the original shape of a support, including bulges, depressions, cockling, or undulations.

Other term: deformation from plane

Dent

A concave distortion on the front surface of a painting. Dents are caused by a blow or by pressure from another object.

Draws

Ripples in the canvas radiating from the corners (corner draws) or edges of a painting. Draws occur during exposure to low relative humidity (e.g., during winter), and may disappear when moderate relative humidity returns.

Edge-strips

Thin protective strips of wood or metal attached to the four sides of a painting and extending above the paint surface. Edge-strips are used to isolate the paint surface from the rabbet of the frame. (See Figure 1.)

Facing

A reinforcing material, usually tissue paper, temporarily adhered to the surface of a painting. Facing ensures that loose paint particles are temporarily secured, and protects the paint surface during conservation treatment.

Fill

Material replacing lost paint or paint and ground so that the area of loss becomes level with surrounding paint.

Other terms: infill, infilling, luting

Flaking

An unstable condition in which particles of paint or paint and ground become detached.

Gouge

A concavity or impression caused by material being scooped out from the surface of a painting, support, auxiliary support, or frame.

Grime

A disfiguring deposit on or ingrained in the surface of a painting. Grime is often a combination of air-borne soot, nicotine, cooking oils, smudges, and finger and palm marks.

Other term: Surface dirt

Ground

An opaque white or coloured coating applied to the support as a base for the paint layers. The materials used for the ground vary.

Other term: Priming

Impasto

Pronounced brush strokes or a thick application of paint standing in relief on the surface of a painting. Impasto may be a thick or simply a slight build-up on an otherwise smooth surface.

Imprimatura

A thin layer of paint applied over the ground by the artist to provide the base tones for the painting.

Inpainting

Applying new paint on areas where original paint has been lost or abraded.

Other term: Retouching

Keys

Small wedges inserted into slots at the corners of a stretcher. Tapping the wedges and driving them further into their slots forces the comers apart and expands the stretcher. This is called "keying out".

Other term: wedges

Lifting

A form of deterioration in which pieces of paint or paint and ground are partially detached and elevated above the paint surface.

See also: Cleavage, Flaking, Tenting

Liner

The inside portion of a frame that borders the painting. Liners are constructed separately from the frame, but are usually secured to the frame and can become loose or detached.

Lining

The process of adhering a new fabric to the back of a painting on canvas. Lining also refers to the fabric itself. Applying a new fabric to the back of a painting that has previously been lined is called relining.

Loose lining

A fabric stretched directly behind, but not adhered to, a painting on canvas. Loose lining provides protection and additional support to the painting.

Other term: blind lining

Loss

An area where paint or paint and ground are missing because of damage or deterioration.

Other term: lacuna

Marouflage

The process of adhering a painting to a rigid auxiliary support panel.

Medium

The film-forming material that holds together the pigment particles in paint, such as drying oil in oil paint and vegetable gum in watercolour paint.

Other terms: Binder, vehicle

Mitre joint

The corner where the horizontal and vertical bars of a stretcher or strainer are each cut at a 45° angle so that when they meet they form a 90° angle. Stretchers should ideally have mitred joints; otherwise, distortions in the canvas could occur when the stretcher is expanded. (See Figure 3.)

A Mitre joint.
Figure 3. Mitre joint.

Overpaint

Paint, not applied by the artist, that covers original paint and that is often an excessive and unnecessary alteration to the image. Overpaint hides areas of damage or is used to make cosmetic changes to the image.

Paint

A film-forming material composed of pigment and a medium such as oil, resin, gum or glue.

Panel

A rigid primary or secondary support of wood or metal. Traditionally, a panel was a wooden board or a number of boards joined together. Now, it also refers to supports such as masonite, hardboard, or plywood.

Other term: solid support

Pentimento

An original design that was changed by the artist. Pentimento may be visible because of textural differences in the paint surface or because of increased transparency of the overlying paint.

Pigment

Coloured particles in powder form that become paint when combined with a medium.

Priming

See Ground.

Puncture

A small hole through a painting. A puncture may accompany a deformation in the surface, and is caused by an impact.

Rabbet

The recess in a frame against which a painting rests.

Other term: rebate

Relining

Applying a new fabric to the back of a painting that has previously been lined. Relining usually involves removing the previous lining fabric and adhesive before applying new fabric with fresh adhesive.

Retouching

A traditional term that has been used synonymously with inpainting. However, inpainting is more precise because retouching can also imply overpainting so that original paint is covered.

Selvedge

The original woven edge of a piece of fabric where the weft threads return over the warp threads. A selvedge usually has a tightly woven "finished" edge.

Other term: selvage

Sight edge

The visible perimeter of a painting, not the actual edge that is hidden under the rabbet of the frame. (See Figure 4.)

A Sight edge.
Figure 4: Sight edge.

Size

A solution or gel applied to raw canvas or to a wooden support before the ground layer is applied. Size reduces the absorbency of the support. Traditionally, skin glues, gelatin, gum, or starch were used. Modern materials include acrylic formulations.

Other term: sizing

Skinning

Abrasion of original paint by inexpert cleaning. Skinning often emphasizes the weave of the canvas, since paint is removed from the raised portions of the painting's surface.

Other term: over-cleaning

Split

A complete separation through a piece of wood along the grain.

Strainer

A wooden frame with fixed, non-expandable corners over which a painting canvas is stretched. Strainers are auxiliary supports for paintings. Strainers should not be confused with stretchers, which are expandable.

Strainer bars

The four principal wooden parts of the strainer.

Cross bar(s)

Extra horizontal or vertical part(s) added to strengthen the strainer.

Other term: cross brace

Stretcher

A wooden frame with expandable corners over which a painting canvas is stretched. Stretchers are auxiliary supports for paintings.

Stretcher bars

The four principal wooden parts of the stretcher.

Cross bar(s)

Extra horizontal or vertical part(s) added to strengthen the stretcher.

See also: Bevel, Mitre joint, Strainer

Stretcher mark

A line of cracks or a deformation in the painting surface that follows the inside edges of the stretcher or strainer parts.

The image of the stretcher or strainer is also sometimes visible because of relatively crack-free areas immediately above the stretcher or strainer. These crack-free areas result from the humidity-buffering capacity of the wood from which the stretcher or strainer is made.

Other term: stretcher crease

Support

Any material, such as canvas, wood, paper, ceramic, metal, glass, ivory, or plastic, that carries the ground and paint layers.

Composite support

Two or more materials forming the support, such as canvas adhered to cardboard or to Masonite.

Primary and secondary support

In a composite support, the primary support lies directly below the ground and paint layers, and is supported by the secondary support. For example, when canvas is adhered to Masonite hardboard, the primary support is the canvas and the secondary support is the Masonite hardboard.

Rigid support

A support material such as wood, Masonite, or metal.

Other term: solid support

Surface coating

A transparent layer or series of layers applied to the surface of a finished painting. Various materials are used as surface coating, including natural resins, drying oils, waxes, and, more recently, synthetic resins.

Other term: surface film

Surface dirt

A deposit of dust, dirt, grime, nicotine, soot, or other contaminant on the surface of a painting.

Tacking margin

The part of a canvas that wraps around the edges of the stretcher or strainer and that is held by tacks or staples.

Other term: tacking edge

Tear

Where fabric or paper has been forcibly pulled apart, leaving ragged or irregular edges.

Tension garland

Scalloped pattern along the edges of the canvas indicating where the original tacks held the fabric to an auxiliary support. Tension garland is useful for approximating the original dimensions of paintings that may have changed in size. Anomalies in the tension garland can also indicate that the canvas was stretched for priming before being mounted onto the original painting stretcher.

Other terms: scalloping, stress garland, stretcher garland

Tenting

A type of cleavage where the paint or paint and ground layers are cracked and are forced upward in a tent shape. Tenting is caused by compression from shrinkage in the canvas or wood support.

Turn-over edge

The edge of a fabric-supported painting where the canvas is first turned over the auxiliary support.

Varnish

A clear solution of resin dissolved in oil or solvent, which dries to form a transparent film. Traditional varnishes consist of natural resins, such as mastic, dammar, or copal. Recently, various synthetic resins have been used. Varnish is usually used as a final surface coating over a finished painting to even out the gloss, to saturate the colours, and to protect the paint.

Warp

A distortion, such as a bend or curve, in a rigid or semi-rigid material. Warp also refers to the threads in a fabric that run parallel to the selvedge edge.

Weave

The pattern created by overlapping warp and weft threads in a woven fabric.

Plain (tabby) pattern

One weft thread woven alternately over the warp threads. (See Figure 5.)

Plain pattern weave.
Figure 5. Plain (tabby) pattern weave.

Twill pattern

A complex weave that creates a diagonal pattern on the cloth. (See Figure 6.)

A Twill pattern weave.
Figure 6. Twill pattern weave.

Weft

The threads in a fabric that run at right angles to the selvedge edge.

Wrinkle

A condition in a paint or varnish film in which the surface exhibits puckers, ridges, and furrows that occurred during drying.