Rabbit-skin glue
Encyclopedia
Rabbit-skin glue is a sizing
that also acts as an adhesive
. It is essentially refined rabbit collagen
, and was originally used as an ingredient in traditional gesso
.
painter, skin glue was used to coat the canvas. This is necessary because the linseed oil
that forms the base of most oil paint contains an acid, linolenic acid, that will over time destroy the canvas fibers.
Manufacturers of rabbit, and cow & horse hide glue recommend dissolving at 60-63C (140-145F).
of concertina
s, and in other smaller, light instruments-- prominently in violins. Its supreme advantages are very fast bonding; and easy debonding with hot water if an instrument must be disassembled for internal repairs. It also has very low creep, which is the tendency of some glues to plastically yield under even low but consistent stresses over time. For example, guitar bridges are subject to high lateral stresses that with the wrong glue can lead it to creep forward.
The proteins of the glue soak into the wood and interlace with its pores. Setting of the glue occurs with cooling and drying, so the working time is very short, on the order of minutes, to stick the parts together and get full strength, unlike PVA
glue which might provide 20-30 minutes.
Furthermore, since the glue only works by microscopically stitching the wood fibers together, any gaps in the joint are not going to be successfully filled, and so the mating surface must be very smooth.
is then applied. A canvas sized with rabbit-skin glue can be made tighter than with other alternatives—such as an acrylic
-based gesso—because of the shrinkage. This type of canvas is also valuable because it can be sanded to a flatter texture, which allows the painter to achieve a finer level of detail than can be achieved with a typical acrylic gesso ground.
This rabbit-skin glue ground is only appropriate for use under oil paint. Acrylic-based media will flake off a canvas prepared with rabbit-skin glue and are therefore not appropriate.
Rabbit skin glue is considered to be a major cause of cracking in oil paintings by most modern conservators. Because the glue is hygroscopic, it continually absorbs moisture from the atmosphere, causing the glue to swell and shrink. Over time, this constant flexing causes the brittle oil paint to crack. Modern substitutes for rabbit skin glue are available, such as Gamblin’s PVA size and Golden Acrylics’ GAC100. These substitutes do not have the hygroscopic properties of rabbit skin glue, while still being very slightly hygroscopic, and should not cause the damage to oil paints that rabbit skin glue does. However, these modern replacements do not stiffen and tighten the canvas as well as rabbit skin glue does, so some artists still prefer to use rabbit skin glue.
Sizing
Sizing or size is any one of numerous specific substances that is applied to or incorporated in other material, especially papers and textiles, to act as a protecting filler or glaze....
that also acts as an adhesive
Adhesive
An adhesive, or glue, is a mixture in a liquid or semi-liquid state that adheres or bonds items together. Adhesives may come from either natural or synthetic sources. The types of materials that can be bonded are vast but they are especially useful for bonding thin materials...
. It is essentially refined rabbit collagen
Collagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...
, and was originally used as an ingredient in traditional gesso
Gesso
Gesso is a white paint mixture consisting of a binder mixed with chalk, gypsum, pigment, or any combination of these...
.
History
In traditional oil painting as practiced by the RenaissanceRenaissance
The Renaissance was a cultural movement that spanned roughly the 14th to the 17th century, beginning in Italy in the Late Middle Ages and later spreading to the rest of Europe. The term is also used more loosely to refer to the historical era, but since the changes of the Renaissance were not...
painter, skin glue was used to coat the canvas. This is necessary because the linseed oil
Linseed oil
Linseed oil, also known as flaxseed oil, is a clear to yellowish oil obtained from the dried ripe seeds of the flax plant . The oil is obtained by cold pressing, sometimes followed by solvent extraction...
that forms the base of most oil paint contains an acid, linolenic acid, that will over time destroy the canvas fibers.
Production
Rabbit skin glue can be bought in powder form or in larger chunks. Preparation involves using the correct proportion of water to glue to achieve the correct consistency and strength. It should be heated to just short of the boiling point. Too much heat results in a product with reduced adhesive qualities.Manufacturers of rabbit, and cow & horse hide glue recommend dissolving at 60-63C (140-145F).
Adhesive
As an adhesive, Rabbit-skin glue is used in the production of the bellowsBellows
A bellows is a device for delivering pressurized air in a controlled quantity to a controlled location.Basically, a bellows is a deformable container which has an outlet nozzle. When the volume of the bellows is decreased, the air escapes through the outlet...
of concertina
Concertina
A concertina is a free-reed musical instrument, like the various accordions and the harmonica. It has a bellows and buttons typically on both ends of it. When pressed, the buttons travel in the same direction as the bellows, unlike accordion buttons which travel perpendicularly to it...
s, and in other smaller, light instruments-- prominently in violins. Its supreme advantages are very fast bonding; and easy debonding with hot water if an instrument must be disassembled for internal repairs. It also has very low creep, which is the tendency of some glues to plastically yield under even low but consistent stresses over time. For example, guitar bridges are subject to high lateral stresses that with the wrong glue can lead it to creep forward.
The proteins of the glue soak into the wood and interlace with its pores. Setting of the glue occurs with cooling and drying, so the working time is very short, on the order of minutes, to stick the parts together and get full strength, unlike PVA
PVA
PVA may refer to:* Paralyzed Veterans of America* Patrick Van Aanholt , a Dutch footballer playing for Chelsea F.C.* Patterned vertical alignment, an LCD technology* Penn Virginia Corporation * Perkiomen Valley Academy...
glue which might provide 20-30 minutes.
Furthermore, since the glue only works by microscopically stitching the wood fibers together, any gaps in the joint are not going to be successfully filled, and so the mating surface must be very smooth.
Sizing
When used in painting as a sizing, it is spread thoroughly over a canvas that has been placed on the stretcher. When the glue dries, it tightens the canvas. After this has been allowed to dry, an oil-based primerPrimer (paint)
A primer is a preparatory coating put on materials before painting. Priming ensures better adhesion of paint to the surface, increases paint durability, and provides additional protection for the material being painted.-When primers are used:...
is then applied. A canvas sized with rabbit-skin glue can be made tighter than with other alternatives—such as an acrylic
Acrylic paint
Acrylic paint is fast drying paint containing pigment suspension in acrylic polymer emulsion. Acrylic paints can be diluted with water, but become water-resistant when dry...
-based gesso—because of the shrinkage. This type of canvas is also valuable because it can be sanded to a flatter texture, which allows the painter to achieve a finer level of detail than can be achieved with a typical acrylic gesso ground.
This rabbit-skin glue ground is only appropriate for use under oil paint. Acrylic-based media will flake off a canvas prepared with rabbit-skin glue and are therefore not appropriate.
Rabbit skin glue is considered to be a major cause of cracking in oil paintings by most modern conservators. Because the glue is hygroscopic, it continually absorbs moisture from the atmosphere, causing the glue to swell and shrink. Over time, this constant flexing causes the brittle oil paint to crack. Modern substitutes for rabbit skin glue are available, such as Gamblin’s PVA size and Golden Acrylics’ GAC100. These substitutes do not have the hygroscopic properties of rabbit skin glue, while still being very slightly hygroscopic, and should not cause the damage to oil paints that rabbit skin glue does. However, these modern replacements do not stiffen and tighten the canvas as well as rabbit skin glue does, so some artists still prefer to use rabbit skin glue.