Difference between revisions of "Shrunken leather - leather shrinkage"

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Bemerkenswert ist hierbei jedoch, dass [[Chromgerbung|Chromleder]] zwar später schrumpfen als [[Chromgerbung#FOC = Free of Chrome|chromfrei]] gegerbte Leder - dann jedoch deutlich stärker. [[Synthetische Gerbung|Synthetisch gegerbte]] Leder beispielsweise schrumpfen zwar bereits ab 75 Grad Celsius, werden sich dann jedoch nicht so ausgeprägt zusammenziehen wie Chromleder.  
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[[Chrome tanned]] leather shrinks later than [[Chrome tanned#Chrome-free leather - FOC = Free of Chrome|chrome-free]] leather, but then significantly stronger. [[Synthetic tanned]] leather starts shrinking at 75 degrees Celsius, but will not contract as strongly as chrome leather.
  
A problem of [[Chrome tanned#Chrome-free leather - FOC = Free of Chrome|chrome-free (FOC)]] [[synthetic tanned]] leather is the sensitivity to moisture in the leather plus heat. Approx. 50% of all [[car leather]] is FOC. If a convertible comes into the rain, a liquid runs out or a wet towel or a wet swim suit remains too long on the leather, moisture migrates through the [[finish]], the [[Leather seams|seam holes]] or the [[Perforated leather|perforation holes]]. If sun shines on such wet leather, the matrix water (chemically bound in leather) starts boiling and the leather hardens and shrinks.
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A problem of [[Chrome tanned#Chrome-free leather - FOC = Free of Chrome|chrome-free (FOC)]] [[synthetic tanned]] leather is the sensitivity to moisture in the leather plus heat. Approx. 50% of all [[car leather]] is FOC. If a convertible comes into rain, a liquid runs out or a wet towel or a wet swim suit remains too long on the leather, moisture migrates through the [[finish]], the [[Leather seams|seam holes]] or the [[Perforated leather|perforation holes]]. If sun shines on such moistered leather, the matrix water (chemically bound in leather) starts boiling and the leather hardens and shrinks.
  
  
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The moisture of leather also has an effect on the shrinkage temperature. Dry leather is more stable than wet leather. Since leather absorbs the surrounding air humidity, the parameter "moisture" must be considered in critical applications of leather.
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The moisture of leather has an effect on the shrinkage temperature. Dry leather is more stable than wet leather. Since leather absorbs the surrounding air humidity, the parameter "moisture" must be considered in case of critical applications of leather.
 
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Die Feuchtigkeit eines Leders hat auch einen Einfluss auf die Schrumpftemperatur. Trockene Leder sind temperaturstabiler als feuchte Leder. Da Leder die umgebende Luftfeuchtigkeit aufnimmt, muss der Parameter „Feuchtigkeit“ bei kritischen Einsatzzwecken des Leders mit beachtet werden.
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''Rückbank oben bei einem [[Oldtimer]]. - Geschrumpftes Armaturenbrett vom Peugeot 307CC.''<br></p>
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''Rear upholstery, above area of a [[Vintage & Classic car leather|classic car]]. - Shrunken [[Leather dashboard|dashboard]] leather of the Peugeot 307CC.''<br></p>
 
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''Kopfstütze durch Sonne geschrumpft. - Brandloch im [[Möbelleder|Sofa]] durch gefallene Lampe.''<br></p>
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''Shrunken Headrest by sun. - Fire hole in [[leather furniture]] by fallen lamp.''<br></p>
 
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Bereits während des Gerbvorgangs selbst muss die Temperatur, der das Leder ausgesetzt wird, ständig kontrolliert werden. [[Haut|Rohhäute]] und [[Blöße|Blößen]] beispielsweise sollten nicht mit mehr als 30 Grad Celsius konfrontiert werden, da ihre Stabilität gegenüber Temperatureinflüssen noch gering ist. Während der Gerbung selbst wird generell der Temperaturbereich von 50 bis 70 Grad Celsius eingehalten. Weiterhin ist die Temperatur zu überwachen bei der [[Trocknen|Trocknung]], der [[Zurichtung]] sowie dem [[Prägung|Prägen]] des Leders.  
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Even during the [[tanning leather|tanning process]], the temperature to which the leather is exposed must be constantly checked. [[Rawhide]] should not be exposed to more than 30 degrees Celsius, since its stability against temperature influences is still low. During the tanning process, a temperature range from 50 to 70 degrees Celsius is generally kept. Furthermore, the temperature is to be monitored during [[Drying leather|drying]], [[finish]] and [[Embossed leather|embossing]] of the leather.
  
  
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''Die Rückbank vom [[Autoleder#BMW|BMW E30 Cabrio]] ist besonders anfällig für Hitzeschäden''<br></p>
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''The rear upholstery top of the [[car leather#BMW|BMW E30 convertible]] is particularly prone to heat damages.''<br></p>
 
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''Unerklärliche Schrumpfung nur einzelner Felder auf der Rückbank eines [[Autoleder|Volvos]]. Linkes Bild: Nur hintere Fläche Sitz. - Rechtes Bild: Geräuschvoll aufgeplatztes Leder im Rückenpolster.''<br></p>
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''Unexplained shrinkage of individual fields on the [[car leather|back seat]] of a volvo. - Left picture: Only rear surface seat. - Right picture: Cracked leather in the back upholstery.''<br></p>
 
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''Links: Nicht selten: Halogenlampe. - Rechts: Ausgelaufene Flüssigkeit. Das Ziehen der Falten zur Schrumpfstelle ist typisch.''<br></p>
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''Left: halogen lamp. - Right: Expired hot liquid. Pulling of folds to the shrunken area is typical.''<br></p>
 
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''Bei Stoff hätte das Haus gebrannt. Hitzeschaden im Leder durch Rotlichtlampe.''<br></p>
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''In case of cloth, the house would have burnt. Heat damage in the leather cause by a lamp.''<br></p>
 
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== Cockpit-Leder - [[Armaturenbrett mit Leder bezogen|Armaturenbrett-Leder]] - Pre-Shrunk Leather ==
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== [[Leather dashboard|Dashboard leather]] - Pre-Shrunk Leather ==
Automobilhersteller und deren Zulieferer machen sich das Schrumpfungsverhalten von Leder übrigens zunutze - etwa zur Verkleidung von [[Armaturenbrett mit Leder bezogen|Armaturenbrettern]]. Um einerseits Formstabilität am zu verkleidenden Gegenstand zu erreichen und andererseits zu gewährleisten, dass das Leder auch unter den Praxisbedingungen im Auto (Sonneneinstrahlung und ggf. hohe Luftfeuchtigkeit!) stabil bleibt, wird das Leder in der Produktion manchmal "vorgeschrumpft" ('''Pre-shrunk leather'''). Dieses sogenannte '''heat setting''' wird durchgeführt, indem das Leder für kurze Zeit Temperaturen von mehr als 100 Grad Celsius ausgesetzt wird - lang genug, um eine dauerhafte Form zu erzielen, aber auch ausreichend kurz, damit das Leder nicht unbrauchbar wird.
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Automotive manufacturers and their suppliers are taking advantage of the shrinking behavior of leather to trim [[Leather dashboard|dashboards]]. In order to achieve shape stability and to ensure that the leather remains stable even under the practical conditions in the car (sunshine and possibly high humidity), the leather is sometimes "pre-shrunken". This so-called "heat setting" is carried out by exposing the leather to short-term temperatures of more than 100 degrees Celsius. Long enough to achieve a lasting shape, but also short enough to prevent the leather becoming unusable.
  
  
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''Armaturenbrett komplett mit Leder bezogen.''<br></p>
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''[[Leather dashboard|Dashboard]] completely covered with leather.''<br></p>
 
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Auch der eingesetzte Kleber spielt eine wichtige Rolle. Der Kleber muss fester sein als die Kräfte bei der Schrumpfung des Leders. auch dann kommt es nicht zu Schäden.  
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The used adhesive also plays an important role. The adhesive must be stronger than the forces of shrinkage of the leather. This can prevent shrinkage damages.  
  
  
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''Geschrumpfte [[Armaturenbrett mit Leder bezogen|Armaturenbretter]] vom Peugeot 307CC''<br></p>
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''Shrunken [[Leather dashboard|dashboard]] leathers of the Peugeot 307CC.''<br></p>
 
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Revision as of 13:47, 12 February 2017

LEATHER-DICTIONARY.jpg


Shrinkage of leather caused by heat

Leather can shrink and harden by excessive heat. Typical is damaged car leather at the top along the rear bench, the headrests and on dashboards. Leather also hardens because it dries out with time (without leather care). The leather fibers stiffen and become brittle.

This process is accelerated by the fact that the collagen of the fibers then denatures with release of the water previously bound in them. Initially, small singulated thickenings are formed in the leather fibre struccture, which subsequently expand and solidify. The density of the leather increases, but its dimensions decrease. This hardening is extremely stable. Once shrunken leather is therefore irreparably damaged and can sometiems be softened a little with appropriate care products, but the loss of surface is permanent and can not be recovered.

For wet leathers, even little heat is sufficient to shrink it. Wet leather should never be allowed to dry in the sun or on a heater. The best temperature to dry leather is normal room temperature.


Video about the shrinkage of leather.


Welle oiled and greased leather will never shrink as quickly as poorly maintained leather. The tanning methode of the leather directly influences its shrinkability. Traditionally vegetable-tanned leather already begin to shrink at 70 degrees Celsius. This looks like a high temperature, but which is reached quickly, when a convertible with wet, dark leather seats is put into the sun for drying. The leather is then "cooked" and shrinks. Modern tanning processes, such as chrome tanning, raise the threshold of leather shrinkage so that such leather starts shrinking between 85 to 110 degrees Celsius.


Condition/tanning methode Shrinkage temperature
Rawhide 60°C - 65°C (140 - 149 °F)
After pickling before tanning 40°C - 60°C (104 - 140 °F)
Vegetable-tanned leather 70°C - 80°C (158 - 176 °F)
Chrome tanned 85°C - 100°C (185 - 212 °F)
Synthetic tanned 75°C - 85°C (167 - 185 °F)
Chamois leather 60°C - 70°C (104 - 158 °F)


Chrome tanned leather shrinks later than chrome-free leather, but then significantly stronger. Synthetic tanned leather starts shrinking at 75 degrees Celsius, but will not contract as strongly as chrome leather.

A problem of chrome-free (FOC) synthetic tanned leather is the sensitivity to moisture in the leather plus heat. Approx. 50% of all car leather is FOC. If a convertible comes into rain, a liquid runs out or a wet towel or a wet swim suit remains too long on the leather, moisture migrates through the finish, the seam holes or the perforation holes. If sun shines on such moistered leather, the matrix water (chemically bound in leather) starts boiling and the leather hardens and shrinks.


Synthetic-tanned-car-leather-damage-01.jpg Synthetic-tanned-car-leather-damage-02.jpg

Shrinkage of synthetic tanned car leather due to moisture in leather and the heat of the sun.

 

The moisture of leather has an effect on the shrinkage temperature. Dry leather is more stable than wet leather. Since leather absorbs the surrounding air humidity, the parameter "moisture" must be considered in case of critical applications of leather.


Hitzeschaden-03-Rueckbank.jpg Peugeot-307CC-Armaturenbr-2.jpg

Rear upholstery, above area of a classic car. - Shrunken dashboard leather of the Peugeot 307CC.

 

Hitzeschaden-02-Kopfstuetze.jpg Hitzeschaden-01-Sofa.jpg

Shrunken Headrest by sun. - Fire hole in leather furniture by fallen lamp.

 

Even during the tanning process, the temperature to which the leather is exposed must be constantly checked. Rawhide should not be exposed to more than 30 degrees Celsius, since its stability against temperature influences is still low. During the tanning process, a temperature range from 50 to 70 degrees Celsius is generally kept. Furthermore, the temperature is to be monitored during drying, finish and embossing of the leather.


Hitzeschaden-07-BMW-E30.jpg Hitzeschaden-06-BMW-E30.jpg

Hitzeschaden-05-BMW-E30.jpg Hitzeschaden-04-BMW-E30.jpg

The rear upholstery top of the BMW E30 convertible is particularly prone to heat damages.

 

Volvo-Schrumpfung-01.jpg Volvo-Schrumpfung-02.jpg

Unexplained shrinkage of individual fields on the back seat of a volvo. - Left picture: Only rear surface seat. - Right picture: Cracked leather in the back upholstery.

 

Hitzeschaden-Lampe-01.jpg Möbel-Schrumpfung-01.jpg

Left: halogen lamp. - Right: Expired hot liquid. Pulling of folds to the shrunken area is typical.

 

Moebelleder-Hitzeschaden-01.jpg Moebelleder-Hitzeschaden-02.jpg

In case of cloth, the house would have burnt. Heat damage in the leather cause by a lamp.

 

Dashboard leather - Pre-Shrunk Leather

Automotive manufacturers and their suppliers are taking advantage of the shrinking behavior of leather to trim dashboards. In order to achieve shape stability and to ensure that the leather remains stable even under the practical conditions in the car (sunshine and possibly high humidity), the leather is sometimes "pre-shrunken". This so-called "heat setting" is carried out by exposing the leather to short-term temperatures of more than 100 degrees Celsius. Long enough to achieve a lasting shape, but also short enough to prevent the leather becoming unusable.


Armaturenbrett-01.jpg

Dashboard completely covered with leather.

 

The used adhesive also plays an important role. The adhesive must be stronger than the forces of shrinkage of the leather. This can prevent shrinkage damages.


Peugeot-307CC-Armaturenbret.jpg

Peugeot-307cc-01.jpg Peugeot-307cc-02.jpg

Shrunken dashboard leathers of the Peugeot 307CC.

 



Shrinkage of leather in the tannery

Since leather is sold by surface, the tanner tries to get an as large as possible hide by the tanning process. However, leathers are sometimes deliberately shrunken, so that the leather becomes thicker and the grain pattern is reenforced. Such treatments are known in the case of cow neck leather and sheep leather. The company www.brocantique.de is a specialist for vegetal tanned sheep leather shrinkage. When shrinking sheep leather, it loses up to 20% of the surface and becomes thicker.


Sheep leather-01.jpg

Shrunken sheep leather (www.brocantique.de).

 

Additional information


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