Animal glue

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Animal glue

An animal glue is an adhesive

Adhesive

Adhesive or glue is a compound in a liquid or semi-liquid state that adhesion or bonds items together. Adhesives may come from either natural or Chemical synthesis sources....
that is created by prolonged boiling of animal

Animal

Animals are a major group of multicellular, eukaryotic organisms of the Kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life....
connective tissue

Connective tissue

Connective tissue is a form of fibrous biological tissue.It is one of the four types of tissue in traditional classifications .Collagen is the main protein of connective tissue in animals and the most abundant protein in mammals, making up about 25% of the total protein content....
.

These protein

Protein

Proteins are organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid Residue ....
colloid

Colloid

A colloid is a type of chemical mixture where one substance is dispersed evenly throughout another. The particles of the dispersed substance are only suspended in the mixture, unlike a solution, where they are completely dissolved within....
glues are formed through hydrolysis

Hydrolysis

Hydrolysis is a chemical reaction during which one or more water are split into hydrogen and hydroxide ions which may go on to participate in further reactions....
of the collagen

Collagen

Collagen is the main protein of connective tissue in animals and the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content....
from skins, bones, tendons, and other tissues, similar to gelatin

Gelatin

Greek language

Greek is an Indo-European languages native to the southern Balkan peninsula, the language of the Greek people. It forms an independent branch within Indo-European....
kolla, glue. These proteins form a molecular bond with the glued object.

Stereotypically

Stereotype

A stereotype is a preconceived idea that attributes certain characteristics to all the members of class or set. The term is often used with a negative connotation when referring to an oversimplified, exaggerated, or demeaning assumption that a particular individual possesses the characteristics associated with the class due to his or her me...
, the animal in question is a horse

Horse

The horse is a hoofed mammal, a subspecies of one of seven extant species of the family Equidae. The horse has evolution of the horse over the past 45 to 55 million years from a small multi-toed creature into the large, odd-toed ungulate animal of today....
, and horses that are put down are often said to have been sent to the "glue factory".

al glue was the most common woodworking glue for thousands of years until the advent of synthetic glues such as polyvinyl acetate

Polyvinyl acetate

Polyvinyl acetate is a rubbery synthetic polymer. PVA is a common copolymer.It is prepared by polymerization of vinyl acetate, also referred to as VAM....
(PVA) and other resin glues in the 20th century.

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Encyclopedia

An animal glue is an adhesive

Adhesive

Animal

Connective tissue

Protein

Colloid

Hydrolysis

Hydrolysis is a chemical reaction during which one or more water are split into hydrogen and hydroxide ions which may go on to participate in further reactions....
of the collagen

Collagen

Gelatin

Greek language

Stereotype

Horse

Types and uses

Animal glue was the most common woodworking glue for thousands of years until the advent of synthetic glues such as polyvinyl acetate

Polyvinyl acetate

Luthier

A luthier is someone who makes or repairs stringed instruments. The word luthier comes from the French language word wikt:en:luth#French which is French for "lute"....
, pipe organ building

Pipe organ

The pipe organ is a keyboard musical instrument that produces sound by venting mechanically compressed air through resonant Organ pipe. Each pipe produces sound at one fixed pitch, so they are provided in sets or "ranks" with one pipe or more per note, each rank having a common timbre and loudness throughout....
, and antique restoration. Glass artists take advantage of hide glue's ability to bond with glass, applying hide glue to glass. As the glue hardens it shrinks, chipping the glass.

It has several advantages and disadvantages compared to other glues. The glue is applied hot, typically with a brush

Brush

The term brush refers to devices with bristles, wire or other filaments, used for cleaning, Personal grooming hair, cosmetics making painting, deburring and other kinds of surface finishing, and for many other purposes....
or spatula

Palette knife

A palette knife is a blunt knife with an extremely flexible steel blade and no sharpened cutting edge. It is primarily used for mixing paint colors, paste, etc., or for Paper marbling, decorative endpapers, etc....
; it is kept hot in a glue pot

Glue pot

A glue pot is a pot in which animal glue is heated for use in woodworking and for other purposes. Due to the tendency of collagen, the dominant adhesive in animal glues, to degrade at temperatures above , they are often regulated to a lower temperature to maintain the liquidity of the glue without damaging the glue itself....
. Most animal glues are soluble in water

Water

Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or States of matter, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam....
, useful for joints

Woodworking joints

Alcohol

In chemistry, an alcohol is any organic compound in which a hydroxyl Functional group is bound to a carbon atom of an alkyl or substituted alkyl group....
is sometimes applied to such joints to dehydrate the glue, making it more brittle and easier to crack apart.

Specific types include hide glue, bone glue, fish glue, rabbit skin glue.

Hide glue

Hide glue is used in woodworking. It may be supplied as granules, flakes, or flat sheets, which have an indefinite shelf life

Shelf life

Shelf life is that length of time that food, drink, medicine and other decomposition items are given before they are considered unsuitable for sale or Eating....
if kept dry. It is dissolved in water, heated and applied warm, typically around 140°F

Fahrenheit

Fahrenheit is a temperature scale named after the physicist Daniel Gabriel Fahrenheit , who proposed it in 1724. Today, the scale has largely been replaced by the Celsius scale; it is still in use for non-scientific purposes in the United States and a few other countries such as Belize....
(60°C). Warmer temperatures quickly destroy the strength of hide glue. Commercial glue pots, simple water baths or double boilers may be used to keep the glue hot while in use. As hide glue cools, it gels quickly. At room temperature, prepared hide glue has the consistency of stiff gelatin

Gelatin

Gelatin is a translucent, colorless, brittle, nearly tasteless solid, derived from the collagen inside animals' skin and mostly bones. It has been commonly used as a gelling agent in food, pharmaceutical, photography, and cosmetic manufacturing....
, which is in fact a similar composition. Gelled hide glue does not have significant strength, so it is vital to apply the glue, fit the pieces, and hold them steady before the glue temperature drops much below 120°F (50°C). All glues have an open time, the amount of time the glue remains liquid and workable. Joining parts after the open time is expired results in a weak bond. Hide glue's open time is usually a minute or less. In practice, this often means having to heat the pieces to be glued, and gluing in a very warm room, though these steps can be dispensed with if the glue and clamp operation can be carried out quickly.

Where hide glue is in occasional use, excess glue may be held in a freezer, to prevent spoilage from the growth of microorganism

Microorganism

A microorganism or microbe is an organism that is microscopic . The study of microorganisms is called microbiology, a subject that began with Anton van Leeuwenhoek's discovery of microorganisms in 1675, using a microscope of his own design....
s. Joints

Woodworking joints

Joinery is that part of woodworking that involves joining together pieces of wood, to create furniture, structures, toys, and other items. Some wood joints employ fasteners, bindings, or adhesives, while others use only wood elements....
to be glued with hide glue must fit perfectly, as it has poor gap-filling properties.

Hide glue that is liquid at room temperature is also possible through the addition of urea. An example of this type of mixture is Old Brown Glue, created by W. Patrick Edwards, the director of the American School of French Marquetry. In stress tests performed by Mark Schofield of Fine Woodworking Magazine, liquid hide glue compared favourably to hot hide glue in average strength of bond. "However, any liquid hide glue over six months old can be suspect because the urea eventually hydrolyzes the protein structure of the glue and weakens it— even though the product was 'protected' with various bactericides and fungicides during manufacture."

Properties

This significant disadvantage to using hide glue is offset by several advantages. Hide glue joints are reversible and repairable. Recently glued joints will release easily with the application of heat and steam. Hide glue sticks to itself, so the repairer can apply new hide glue to the joint and reclamp it. In contrast, PVA glues do not adhere to themselves once they are cured, so a successful repair requires removal of the old glue first - which usually requires removing some of the material being glued.

Hide glue creates a somewhat brittle joint, so a strong shock will often cause a very clean break along the joint. In contrast, a joint glued with PVA will usually break the surrounding material, creating an irregular, difficult to repair break. This brittleness is taken advantage of by instrument makers. For example, instruments in the violin

Violin

The violin is a Bow string instrument with four strings usually tuned in perfect fifths. It is the smallest and highest-pitched member of the violin family of string instruments, which also includes the viola and cello....
family require periodic disassembly for repairs and maintenance. The top of a violin is easily removed by prying a palette knife between the top and ribs, and running it all around the joint. The brittleness allows the top to be removed, often without significant damage to the wood. Regluing the top only requires applying new hot hide glue to the joint. If the violin top was glued on with PVA glue, removing the top would require heat and steam to disassemble the joint (causing damage to the varnish), then wood would have to be removed from the joint to ensure no cured PVA glue was remaining before regluing the top.

Hide glue also functions as its own clamp. Once the glue begins to gel, it pulls the joint together. Violin makers may glue the center seams of top and back plates together using a rubbed joint rather than using clamps

Clamp (tool)

A clamp is a fastener to hold or secure objects tightly together to prevent movement or separation through the application of inward pressure. In the United Kingdom and Australia, the term clamp is often used instead when the tool is for temporary use for positioning components during construction and woodworking; thus a C clamp or a sa...
. This technique involves coating half of the joint with hot hide glue, and then rubbing the other half against the joint until the hide glue starts to gel, at which point the glue becomes tacky. At this point the plate is set aside without clamps, and the hide glue pulls the joint together as it hardens.

Hide glue regains its working properties after cooling if it is reheated. This property can be used when the glue's open time does not allow the joint to be glued normally. For example, a cello maker may not be able to glue and clamp a top to the instrument's ribs in the short one minute open time available. Instead, the builder will lay a bead of glue along the ribs, and allow it to cool. The top is then clamped to the ribs. Moving a few inches at a time, the maker inserts a heated palette knife into the joint, heating the glue. When the glue is liquefied, the palette knife is removed, and the glue cools, creating a bond. A similar process can be used to glue veneers to a substrate. The veneer and/or the substrate is coated with hot hide glue. Once the glue is cold, the veneer is positioned on the substrate. A hot object, such as a clothes iron is applied to the veneer, liquefying the underlying glue. When the iron is removed, the glue cools, bonding the veneer to the substrate.

Hide glue joints do not creep under loads. PVA glues create plastic joints, which will creep over time if heavy loads are applied to them.

Hide glue is supplied in many different gram strengths, each better suited to specific applications. Instrument and cabinet builders will use a range from 120-200 gram strength. Some hide glues are sold without the gram strength specified. Experienced users avoid this glue as the glue may be too weak or strong for the expected application.

Hoof glue

Hoof Glue is an adhesive made by boiling down the hoof of ungulates. It is a partially hydrolysis keratin. It is a kind of animal glue....
is also used today in woodworking, specifically cabinetry.

Rabbit-skin glue

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....
is used in the sizing

Sizing

Sizing or size is a substance that is applied to materials as a protecting glaze, filler, or lubricant. It is used to change surface properties in papermaking, gilding, and the manufacture of textiles and fiberglass....
or priming of oil painters'

Oil painting

Oil painting is the process of painting with pigments that are bound with a medium of drying oil ? especially in early modern Europe, linseed oil....
canvas

Canvas

Canvas is an extremely heavy-duty plain weave cloth used for making sails, tents, marquees, backpacks, and other functions where sturdiness is required....
es.

History

Nearly 5,000 years ago, the Egyptians were using hide glue for their furniture

Furniture

Furniture is the mass noun for the movable objects which may support the human body , provide storage, or hold objects on horizontal surfaces above the ground....
adhesive. This is proven by hairs found in Pharaoh

Pharaoh

Pharaoh is a title used in many modern discussions of the ancient Egyptian rulers of all periods. In antiquity this title began to be used for the ruler who was the religious and political leader of united ancient Egypt, only during the New Kingdom, specifically, during the middle of the Eighteenth dynasty of Egypt....
's tomb

Tomb

For the New York prison see The Tombs.A tomb is a repository for the remains of the death. The term generally refers to any structurally enclosed interment space or burial chamber, of varying sizes....
s and by stone carvings depicting the process of gluing different woods. Evidence exists that the Sumer

Sumer

Sumer was a civilization and a historical region located in Southern Iraq , known as the Cradle of civilization. It lasted from the first settlement of Eridu in the Ubaid period through the Uruk period and the Dynastic periods until the rise of Babylon in the early 2nd millennium BC....
ians also used glue before the Egyptians

Egyptians

Egyptians is the name of the nationality and Mediterranean North African ethnic group native to Egypt.Egyptian identity is closely tied to the Geography of Egypt, dominated by the lower Nile Valley, the small strip of cultivable land stretching from the Cataracts of the Nile to the Mediterranean Sea and enclosed by desert both to the Easte...
did.

Animal glue

Types and uses

Hide glue

Properties

Hoof glue

Rabbit-skin glue

History

See also