What is the different between Hide Glue and Gelatine?
In violin making, the beneficial properties of animal glues have always been appreciated. In contrast to synthetic glue, glue with gelatine can be re-opened again at any time with the addition of heat and moisture without causing damage to the workpieces. Synthetic glue remains hard after curing, which can damage musical instruments or furniture. [GME (2/2021)]
What is the history of animal based glues?
Historically, animal glues have been used for a long time. “From 7000 BC, the advanced civilizations in Mesopotamia (Iraq) and Egypt extracted animal components (animal bones, skin, fish waste) through boiling. At the same time, gelatine glue was used in furniture production in Daedalus and Icarus (Near East). The first historical evidence comes from the ancient civilizations of the Mesopotamia between the Euphrates and Tigris, from the sunken city-states: Sumer - Akkad - Assur and Babylon (approx. 4000 BC). The Sumerians consciously and by hand developed an adhesive and wrote history through it. They boiled a kind of glutine glue out of animal skins and seem to have already used asphalt as a binding agent when building their houses and temples. It can also be assumed that tendon backings were used for hunting and war bows at this early point in time, but no archaeological evidence exists. This glue was later refined by the ancient Egyptians. A plaque of hide glue was found in the grave of Tutenchamun, which proves that veneer work was cemented with glue long before the birth of Christ. As early as 3500 BC, the Egyptians were able to produce glue based on protein, which they made by boiling animal hides. As early as 3300 BC hide glue was used in Egypt and secured by a hyroglyphic text. "[Ulmer, R. / Westebbe, P. (SS 2002) p.4]
The first historical evidence for the use of hide glue can be found in a rock chamber in the mortuary temple of Queen Hatshepsut in Egypt from 1500 BC. Here a fresco shows the use of hide glue and thus the gluing of different types of wood. With the fall of the Roman Empire, however, the art of gluing seems to have been forgotten and was only rediscovered in the 16th century. [Baumann, H. (1967)]
Until the late 17th century, glues and gelatine extracts were obtained by boiling bones and pieces of skiin. Between the late 17th and the beginning of the 19th century there were first attempts at production on a craft scale. [Babel, W. (1996) p.4]
Then in 1690 the first artisan glue factory for technical gelatine was founded in Holland. [Baumann, H. (1967)]
It was not until the beginning of the 19th century, as a result of the English sea blockade in France and the associated nutritional deficiencies, that industrial gelatine production was started in order to be able to supply the population with protein. With the advent of photography and its use as a binder for light-sensitive silver haloids [GME (1/2021)], the demand for gelatine increased rapidly, so that by the end of the 19th century, gelatine production on an industrial scale had developed in all industrialized countries. [Babel, W. (1996) p.4]
Terminilogy for animal glue and gelatine production
- Isinglass: cartilage, fish bones [Ottmeier, W. (2/2011) p.26]
- Rabbit glue: glue made from bones and skins of small animals [Ottmeier, W. (2/2011) p.26]
- Isinglass glue: swim bladders of fish [Ottmeier, W. (2/2011) p.26]
- Hide glue, leather glue: animal skins, tendons [Ottmeier, W. (2/2011) p.26]
- Bone glue: bone waste, cartilage, tendons [Ottmeier, W. (2/2011) p.26]
- Button glue: bone glue in the form of drops [Ottmeier, W. (2/2011) p.26]
- Carpenter's glue: generic term for hide and bone glue [Ottmeier, W. (2/2011) p.26]
- Glutine: Purified basic substance from bones, skins etc. and main component of gelatine [Babel, W. (1996) S3.]
- Collagen: protein family made up of long, cross-linked molecular chains, insoluble in water (area of application: food supplements, beauty care products, etc.) [Babel, W. (1996) S3.]
- Gelatine: Long Mollekülketten, soluble in hot water, gelling (application area: gummy bears, glue photo film etc.) [Babel, W. (1996) S3.]
- Collagen peptides: relatively short molecular chains, soluble in hot and cold water, non-gelling (area of application: food supplements, muscle building products, etc.) [Babel, W. (1996) S3.]
- Bloom / Bloom grade: Describes the gel strength according to the AOAC measurement in the gelled, not dried state. The key figure is the mass in grams that is required so that a punch with a diameter of 0.5 inches deforms the surface of a 6.67% gelatine / water mixture four millimetres deep without tearing it. The test takes place standardized at 10 ° C with a previous aging of the gelatine of 17 hours. [GPF (2021] No conclusions can be drawn about the adhesive strength in the dry state from the Bloom value. From my own experience, I can rather conclude the duration of the processing time, but this has not been proven. The AOAC measurement corresponds to the international standard Measurement of the bloom value. Max. Values here are 300-330 bloom. Other measurement methods, which are especially for glue, come to different values.
- Water content: Air-dry gelatine usually contains between 8 and 12% water. With water contents that exceed 16%, there is always the risk of microbiological spoilage. For gluing, this means a reduction in the adhesive properties. [GPF (2021]
- Clarity: The clarity is indicated by the transmission. That means how much light gets through. E.g. LUT Universal: Transmission of 620nm greater than or equal to 85%, transmission of 450nm greater than or equal to 60%
- Viscosity: Here, according to DIN 53260, the flow time is determined that a 10% gelatine solution, at 60 ° C, from a pipette with calibrated capillary determination. This is interesting for the glue because this value relates to the handling temperature. [GPF (2021]
- pH value: In the case of gelatine, this value depends on the salt content and has an effect on the foamability of a gelatine solution. Completely pure gelatine has the pH value of the isoelectric point. The isoelectric point of gelatine is determined by its manufacturing process and is between pH 8.0 and 9.0 for acidic gelatine. In the case of alkaline digested gelatine, the isoelectric point is close to pH 5.0. [GPF (2021]
- Smell and taste: Gelatine has a very low taste or smell of its own. In the case of glue, the smell is caused by impurities or poorly cleaned glue, such as skin, bones, rabbit glue etc.