Horny substance
The horny substance - also known as horn for short - is the hard material that is formed by the skin and consists mainly of keratinized , dead cells ( keratinocytes ) filled with keratin .
From this material mammal, for example, hair , finger and toe nails , claws , jaws , hooves , horns , nose horn of the rhino , spines of the hedgehog , Barten of whales , beaks , and feathers of birds , horny scales and outer armor covering of reptiles constructed.
properties
The horny substance is harder and heavier than wood, but lighter and more elastic than bone. Horn has a length of about 31 km. Its compressive strength is up to 30 kN per square centimeter. It is up to 3% elastic under pressure , i. H. reversibly compressible. Horn is more resilient to compression than to tension; if it is overstrained by bending, it breaks on the tension side. It is non-flammable, not soluble in water and weak alkalis / acids, but in strong alkalis / acids. Pigment-free horn can be translucent (horns of albino animals, human fingernails).
Machining
Similar to wood, horn can be rasped, sawn, drilled, carved, split or sanded. Bleaching is also possible. In order to be able to glue horn, it has to be freed from the claw oil by thorough degreasing , e.g. B. by soaking in gasoline.
Some types of horns tend to delaminate during processing . H. entire layers split off lengthways, especially in the case of cattle horn. On the other hand, if thin pieces / strips of horn are used, the effect may be desirable (e.g. for horn books ).
Horn can be made malleable by soaking it in water for several days. However, it becomes even more malleable if it is boiled for 20 minutes, it can then be bent into almost any shape (thin strips can even be knotted), after cooling and drying the new shape is retained. Horn can also be shaped somewhat by dry heat over the flame.
The largest connected horn plates of up to 3 meters in length are the whale bones ( whalebones ).
use
Before the invention of plastics, horny substance was often used like this. Today it is mainly used for the production of buttons, combs, spoons, knife handles and decorative objects such as carvings, although here too it was often imitated and almost replaced by cheaper plastic. Due to its properties (elasticity, compressive strength, resistance to environmental influences (see above)), however, it is a higher quality material than plastic. When combing z. B. the press seams, which occur in plastic and can damage the keratin of the hair , are missing . It is also ideal as a material for arches, thanks to its reversible deformability (4–5 × larger than that of wood). In addition, the shofar is made of horn, which is blown at the service on the Jewish New Year's Day Rosh Hashanah and at the festival of atonement, Yom Kippur . The horn also goes back to the cattle horns in earlier days.
Other objects that are or were made from horn: the horn book , the composite bow , the corset , waterproof vessels, the powder horn and many more.
Horn chips and horn meal are a valuable nitrogen fertilizer .
See also
Web links
Individual evidence
- ↑ a b Horn and horn products ( Memento from November 15, 2013 in the Internet Archive )
- ↑ http://haarschmuck-guru.de/horn
- ↑ http://books.google.de/books?id=h3H9pjiDsgsC&pg=PA203&lpg=PA203&dq=horn+druckspannung&source=bl&ots=8bS2-z8jAO&sig=kySutaHCHiatBLydysb9YYhtHQg&lpg=de&sa=XR&ei=bY-6ved=de&sa=XR&ei=bY-6ved=de&sa=XR&ei=by-6vepage=en&sa=XR&ei=bY-6fepage=de&sa=XR&ei=bY- vved=de&sa=XR&ei=bY-6fepage=en&sa=XR&ei=bY- 6vved = false