Restoration and conservation terms and definitions
Abrasion
Damage to one or more paint layers, resulting from rubbing, scraping, or other wear .
Accretion
Deposit on the surface of a painting, for example dust, fly spots, food splatters .
Active flaking
Paint and/or ground which is lifting and may be about to flake off .
Age cracking
Pattern of cracks caused by aging, or movement. On canvas paintings they form a web
pattern & may penetrate all layers of the paint and appear as darkened impressions on
the back. On wooden supports cracking a forms a grid pattern along the grain .
Batten/s
Narrow wooden strips attached to the back of wooden panels, across the grain, to lend
extra rigidity to the structure and/or hold together cracked or joined panels .
BEVA 371
Synthetic adhesive which is used as a consolidant and/or as a lining adhesive .
Binding medium
See medium .
Blanching
Bloom on an unvarnished painted surface .
Blind flaking
Separation within a layer, or between layers of paint and ground which is not yet in
danger of flaking off .
Blister
See blind flaking
Bloom
White or bluish-white cloudiness that appears on varnishes, caused by penetration of
the layer by moisture or pollutants .
Buckling
Distortion of a canvas painting, caused by shrinkage or compression, or movement of
the wooden stretcher. Often seen as folds or wrinkles in the corners of paintings. Will
eventually cause damage to paint and ground layers. See also draw .
Button/s
Small bow-shaped wooden battens adhered to the back of wooden panels, usually to
hold cracked, or jointed sections together.
Canvas
Woven fabric on which a picture is painted. Also called the support. Usually made of
linen, cotton or hemp .
Chalking
Paint which appears to be becoming powdery and may look whitish. It is the result of
insufficient binding medium in the paint and some pigment may be lost. Caused either
by the artists poor technique or subsequent damage to the paint layer .
Check
An incomplete split in wood, running along the grain .
Cleaning
Process of removing surface accretions such as dust, dirt, varnish, fly spots or
overpaint from a painting .
Cleavage
See flaking .
Condition Report
A Condition Report is prepared by a conservator, for a client, describing a painting, or
object and the condition it is in at time of examination. See also Frequently Asked
Questions.
Conservation
Steps taken to stabilize, preserve and protect an artwork for as long as possible.
Corner draw
Wrinkles or distortions which form in the corners of stretched paintings on fabric. See
also buckling .
Cotton duck
Woven canvas support which is made of cotton .
Cracking
See craquelure; age cracking & drying cracks .
Cradle
Grid-like arrangement of wooden battens on the back of a wooden panel. A cradle
may or may not be structured to allow some movement of the panel .
Craquelure
Generic term to describe cracking. Specifically, see age cracking; drying/traction
cracks;Sigmoidal/mechanical cracks; crazing .
Crazing
Very fine pattern of cracks .
Cross-bars
Wooden members of a stretcher or strainer which form one or more crosses between
the four outer members. Used to lend greater rigidity and to improve tension .
Cupping
Areas of paint and/or ground which form cups or islands, with their edges lifted and
raised. Severely cupped paint can distort the support .
Curling
See cupping .
Diluent
Liquid, such as water or turpentine, which is used to dilute paint .
Draw
See corner draw .
Dry rot
Timber decay caused by fungi. The cellulose in the wood is consumed, leaving a soft,
weak skeleton.
Drying cracks
Cracks, often very wide, in the paint, ground and/or varnish layers that resemble
alligator-skin or orange peel. They occur when a quick-drying (or lean) layer over a
slow-drying (fat) layer .
Duck
Cotton canvas painting support, see cotton duck .
Easel painting
Painting on canvas, wood, metal, paper or some other portable support .
Efflorescence
Powdery surface crust formed when substances in plaster or varnish crystallize upon
contact with air .
Egg tempera
See tempera .
Estimate of Costs
An Estimate of Costs is prepared by a conservator, for a client, outlining the cost of
proposed conservation and/or restoration treatment. See also Frequently Asked
Questions.
Fat paint
Paint which has a high ratio of medium to pigment, and little diluent, making it very
elastic but slow-drying .
Fill / Filler / Filling
Where paint and ground have been damaged and lost it is usually necessary to insert a
filler so that the area of loss becomes level with surrounding paint. All fillings should
be readily reversible .
Flaking
Loss of adhesion between any or all layers of paint, ground and support. In active
flaking paint and ground has started to fall off .
Fourier Transform Infrared Spectroscopy (FTIR)
Form of microscopic analysis (of samples as small as 10 microns) used for the
classification of organic compounds and some inorganic pigments .
Foxing
Brown or reddish spots on paper and card, caused by mould or the oxidation of iron
particles .
Frame
Outer framing device, often gilded or decorated, which is not part of the painting but
may have been made or commissioned by the artist. Not to be confused with
stretchers or strainers .
Fresco
Wall-painting technique which entails working directly onto wet, freshly applied
plaster .
Gesso
Ground layer, made of animal glue mixed with chalk, applied to the support, to form a
surface on which to paint (usually in egg tempera), or apply gilding .
Ground
Material applied to a support, on top of the size, to prepare it for painting. It is usually
comprised of one or several layers of gesso or oil paint. See also priming .
Glaze
Thin, translucent layer of paint, used to tint the layer/s of paint beneath it .
Glazed/glazing
Refers to the protective glass or Perspex positioned in front on a painting, within its
frame .
Gloss
Subjective term used to describe the relative shininess, or degree of specular
reflection, of a surface .
Glue size
See size .
Impasto
Texture of the painted surface, created by the strokes of the brush or palette knife.
Impasto is more obvious in thick, heavy paint, as troughs and peaks, but the term also
applies to the strokes used to create smoother surfaces .
Incipient flaking
Paint sections or layers which have separated but have not yet begun to fall off. See
flaking .
Infrared Reflectography
Imaging technique for investigating underdrawing. Infrared light penetrates upper
layers of paint to be absorbed by the underdrawing. This absorption can then be
captured by infrared-sensitive camera film .
Inpainting
See retouching/inpainting .
Keys
Flat, triangular, wooden wedges inserted into slots at the corner joints of a stretcher.
They driven into the slots, by degrees, to expand the stretcher .
Lean paint
Paint which has a low ratio of medium to pigment or a high proportion of diluent,
making it non-elastic but fast-drying. See also drying cracks .
Lining
When a new canvas is adhered to the back of a canvas support which has become
badly damaged by tears, or has lost its elasticity and become brittle. Also known as
re-lining .
Loss
Area of missing original paint, ground and/or support .
Mechanical cracking
See Sigmoidal cracking .
Medium
Substance which is used to bind the coloured material in paint. Some examples of
binding media are oil, wax, casein, egg yolk and resin .
Mural
Wall-painting executed onto dry plaster (or on some other support, which is then
attached to the wall). Typically painted in oil, casein and glue-size mediums .
Oil paint
Dry, finely-ground pigment which is made into a paste with an oil, such as linseed,
poppy or walnut. The paste may then be diluted with more oil and/or a spirit such as
turpentine or white spirit .
Original
Those parts of a work of art which are thought to date from the time of its execution,
having been applied by the artist or, under his or her direction, by members of his or
her studio .
Overpainting
Paint, of later application, which partially covers original paint. It may have been
applied at any time after the completion of the picture. Such paint was often applied
by restorers in the past as an easy way to cover and disguise damages .
Paint
Mixture of coloured matter called pigment and a binding medium such as oil, wax,
egg yolk, gelatine, acrylic etc .
Panel
Painting executed on a solid support, typically made of wood, metal, ivory or glass .
Pentimento/ti
Paint may become increasingly translucent with age and the lower layers may become
visible through the upper ones. Typically, underdrawing or changes to the
composition may be seem clearly with the naked eye. An Italian term .
Photomicrograph
Highly magnified image of part of a painting, taken with a camera attached to a
microscope .
Pigment
Coloured material which is finely-ground and then mixed with a binding medium for
use as paint. Pigments can be organic or inorganic and are made from mineral,
vegetable or synthetic sources .
Polarized Light Microscopy (PLM )
Microscopic examination used to identify pigments and fibres .
Priming
Support is traditionally primed with a layer of animal-glue size, followed by one or
more layers of ground, on top of which the painting is executed. See also size and
ground .
Rabbet
See rebate .
Rabbit skin glue
See size .
Raking light
A light source is placed to one side of the painting at a low angle to the surface, so
that it rakes across the painting. This this technique is used in examination and
photography to reveal surface distortions, such as raised paint or undulations .
Rebate
Cut-away groove at the back of the inner edge of a picture frame, which is intended to
receive the painting and hold it in place .
Recommended Treatment Report
A Recommended Treatment Report is prepared by a conservator, for a client,
describing what is required to preserve, stabilize and/or repair a painting, or object.
See also Frequently Asked Questions.
Re-lining
Canvas painting which has already been lined may be re-lined after removal of the old
lining material and adhesive. This may be done when the existing lining or glue has
become degraded or damaged .
Resin
Category of solid or semisolid, viscous substances, both natural (mastic, amber,
copal) and synthetic (polyvinyl, polystyrene). Resins have been important ingredients
in varnishes, adhesives and paints .
Restoration
Repair to artworks that have suffered loss, weakened supports, water, fire, insect and
other chemical and physical damage or deterioration
Retouching/inpainting
Replacing or disguising areas of lost paint by matching the tone and/or colour of the
original paint surrounding the loss. Retouching materials must be inert and reversible
and not extend beyond the area of loss .
Reversible/reversibility
Conservation ethics demand that all materials and processes used by the conservator
should be easily reversed or removed, causing no damage to original material in the
process .
Scumble
Thin layer of semi-opaque paint used to modify a colour already applied .
Sigmoidal/mechanical cracking
Sigmoidal cracks are those which may result from a blow to a canvas painting. They
form a concentric circular pattern which resembles a cobweb. If the canvas has been
scratched or rubbed from behind the mechanical cracks may resemble a feather .
Size
Glue layer applied to a support to promote adhesion between it and the ground layer.
Traditionally rabbit skin or some other animal skin glue is used .
Strainer
Plain frame, usually of wood, over which fabric canvas is stretched to form the
support for a painting. A strainer does not have keys so its size cannot be adjusted
once the canvas is stretched over it. See also stretcher .
Stretcher
Plain frame, usually of wood, over which fabric canvas is stretched to form the
support for a painting. Unlike a strainer, a stretcher has Keys in its joints, which are
used to expand it once the canvas is stretched over it .
Stretcher bar mark
An impression of the stretcher visible on the surface of a canvas painting. These
appear as fairly continuous, parallel, straight cracks in the Paint and Ground layers,
and usually occur when a canvas painting is slack on its stretcher .
Support
Material on which a picture is painted, such as canvas, wooden panel or plastercovered wall. Auxiliary structures, such as stretchers are also referred to as secondary
supports .
Surface dirt
Loose dust or impacted dirt on the surface of a painting or object .
Tacking edge
Part of a fabric canvas support which is folded around the stretcher or strainer and
secured there with tacks or staples. It may be primed and/or painted .
Tempera
Paint which is comprised of finely-ground coloured pigment mixed to a paste with
water, then combined with egg yolk as a binding medium. Tempera may be diluted
with water .
Tenting
Paint and/or ground which has started to flake and has moved outwards from the
support to form pitched tents. Tenting is usually the result of changes in the
dimensions of the support, such as canvas shrinkage .
Traction cracking
See drying cracks .
Transmitted light
A light source is placed behind a canvas painting. The light is transmitted through
paint losses, cracks, tears, and thinly painted areas and the technique is used to
identify possible points of weakness .
Ultraviolet (UV)
Paintings may be examined using UV light. Some painting materials and varnishes
exhibit characteristic fluorescence colours which may used to identify them. UV light
may also identify areas of retouching .
Underdrawing
Preparatory drawing which is subsequently covered with paint. Drawings are often
executed in graphite, charcoal, paint or chalk, using a pencil, pen or brush .
Vacuum table
Plate with a suction device and sometimes a heating element. Used to treat
deformations in supports or to line paintings through the application of gentle, even
pressure and/or heat .
Varnish
Protective coating applied to the surface of painting. There are a wide variety of
varnishes, made of combinations of resin, spirit, oil and wax .
Wall-painting
Picture which is painted directly onto the surface of a wall or onto another support,
such as canvas, which is attached to the wall. Frescoes and murals are examples of
wall-paintings .
Watercolour
Paint which is a combination of very finely-ground coloured pigment mixed to a paste
with water and gelatine. The moist paste is put in tubes or allowed to dry in small
pans. The paint is diluted with water and applied onto supports such as paper .
X-radiography
Used to examine paintings to reveal changes to the composition by the artist and
subsequent losses. Pigments containing heavy metals such as lead absorb X-rays more
than others and X-radiographs register the differences .
X-ray Fluorescence Spectroscopy (XRF)
Method of examination used to identify inorganic pigments through their elemental
constituents.