Animal glues casein

Adhesive Improving cohesion Colophony, gelatine, animal glue, casein... 

Consolidation by organic materials. More commonly, organic polymers have been applied for consolidation of paint layers. Natural polymers were most frequently applied in Europe, including animal glue, casein, egg yolk... 

Adhesives as materials can be classified in a number of ways such as chemical structure or functionality. In this book, adhesives have been classified into two main classes natural and synthetic. The natural group includes animal glue, casein- and protein-based adhesives, and natural rubber adhesives. The synthetic group has been further divided into two main groups industrial and special compounds. Industrial compounds include acrylics, epoxies, silicones, etc. An example of the specialty group is pressure-sensitive adhesives. 

Although natural adhesives (animal glue, casein, starch, and rosin) are still used for many applications, a host of new adhesive materials based on synthetic polymers have been developed these include polyurethanes, polysiloxanes (silicones), epoxies, polyimides, acrylics, and rubber materials. Adhesives may be used to join a large variety of materials—metals, ceramics, polymers, composites, skin, and so on—and the choice of which adhesive to use will depend on such factors as (1) the materials to be bonded and their porosities (2) the required adhesive properties (i.e., whether the bond is to be temporary or permanent) (3) maximum/minimum exposme temperatmes and (4) processing conditions. 

Adhesives of natural origin were mainly used prior to the beginning of the 20th century and by early civilizations as long ago as 2000 BC. These included animal glue, casein, natural rubber and starches. Today, specially developed adhesives based on semi- or fully synthetic products are used for a wide variety of bonding applications (Fig. 8-1). 

Animal glue is a complex colloidal mixture of proteins. The related gelatins are also complex heterogeneous mixtures of proteins. They are strongly hydrophilic and rich in the amino acids glycine, proline, lysine, hydroxyproline and hydroxylysine. Casein is a phosphoprotein obtained from the milk of mammals. 

Proteins Egg, milk and casein, animal glue, silk, wool, vegetable proteins (e.g. garlic, beans), human and animal tissues (e.g. mummies) Paint binders, adhesives, textiles, commodities, parchment... 

Amino acid Egg white Egg yolk Casein Animal glue (collagen) Wool (keratin) Silk (fibroin) Garlic... 

At the same time, natural adhesives such as casein glues, animal glue and polysaccharide gums have gradually been replaced by synthetic adhesives vinyl thermoplastic adhesives [poly(vinyl acetate)], adhesives obtained by reticulation in situ of two components (as epoxy resins), represent very important materials in this field. 

The identification of the proteinaceous binder is done by the evaluation of the amino acid patterns obtained generally egg, casein, animal glue and garlic (garlic being used in gildings [93]) are reported. The amino acid profiles have been processed by different methods and several strategies have been developed to obtain the final identification ... 

Figure 9.2 PCA score plot of amino acidic profiles obtained in the GC/MS analysis of samples from the collection of paint reference materials of Opificio delle Pietre Dure (+), containing egg, casein and animal glue as binders, and of samples from the OL17bis series (x ) from the Leonetto Tintori Collection [ 10]...

Over the centuries the natural organic materials that have best met these requirements are proteinaceous materials (egg, animal glue and casein or milk), polysaccharide gums... 

Though animal glue was used as an adhesive for more than 3000 years but its commercial manufacture started only in 1808. Later on starch, casein and rubber based adhesives also came into use. After 1940, several synthetic resin adhesives have been developed. Polyacrylates are used commercially. 

A safety match requires for its ignition a rubbing on a "striking strip" which is covered with mixture such as consisting of red phosphorus 53, Sb sulfide 42 charcoal 5% in a binder such as NC lacquer, animal glue, dextrin, casein, plus hardener. Sb sulfide and charcoal serve as extenders to the phosphorus. 

Animal glue. mixed with casein and hardener as given in USP 2722484(1955) by I. Kowarsky... 

The major synthetic adhesives used for bonding wood include urea, phenol, and melamine formaldehyde resorcinol formaldehyde, phenol resorcinol, and polyvinyl acetate emulsions. More recently one-component, moisture cured polyurethane adhesives have become popular for bonding wood. Natural adhesives such as casein and animal glues are also often used for general-purpose wood bonding. Epoxies have been used for certain specialized wood joining applications such as when wood is bonded to metal substrates. 

Animal glues are usually made from bones and hide. Casein from milk and fish glues are also of animal origin. 

In contrast to their widespread use in furniture and paper products, animal glues have not proved useful as struetural adhesives for wood. When used as the principal protein constituent, their water sensitivity is excessive compared with other available proteins. When eombined with soybean, blood, or casein, animal gelatin glues are completely hydrolyzed and destroyed by the strong alkalies required to disperse these proteins. In addition, they soften when severely heated, which, by law, prohibits their use in structural wood products [5]. 

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