Report on the POLOLO ShowRoom “Fibre Seminar” on leather

In our second blog article on POLOLO‘s “Fibre Seminar”, we now deal with the topic of leather. The natural leather used by POLOLO nestles against children’s feet like a second skin. Our leather slippers are therefore the best alternative to healthy barefoot walking. This lecture given by Franziska Kuntze was also recorded on film – you can find it at POLOLO on YouTube: “Ecological natural leathers – retailer lecture by POLOLO”.


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Undyed, vegetable-tanned cowhide as an object of demonstration

Kuntze then introduced the topic of natural leather. She brought along a five-square-metre, undyed, vegetable-tanned cowhide that showed traces of life, i.e. it did not have a uniform structure. Leather is a natural product that has been known for thousands of years – to produce it, animal skins have to be made durable by tanning. POLOLO uses nappa or suede leather:
Rough leathers are leathers with a more or less velvety surface. They are also called “nubuck” (grain side). Hunting calf from the flesh split is called “suede” – hunting calf is the generic term for all suede-like surfaces in the leather sector. As a little background knowledge, she told us that today people often talk about buckskin when they actually mean hunting calf – but this is then usually only so-called, as real buckskin actually comes from wild animals such as deer, roe deer etc.

Chromate: Threat to environment, health and reputation

Kuntze reported that today, chromium is mainly used for the leather used in the production of clothing and shoes due to the faster and cheaper tanning process – about 95 per cent of all leather comes from chrome tanning. With controlled processes and established high environmental standards, tanning with chrome is acceptable – in practice, however, the undesirable formation of chromate, which is harmful to health, occurs again and again as a result of incorrect handling. This is considered allergenic and is also suspected of being a carcinogen. In addition, there are considerable wastewater and disposal problems (e.g. chromate may also be formed during the incineration of chrome-tanned leather residues).
Chromate poses a threat to all those involved along the value chain, because leather with a content of three milligrams per kilogram or more is no longer considered marketable. Unfortunately, there are recalls of children’s shoes from time to time – customers often look for cheap offers without paying attention to the quality. A look at the so-called RAPEX list shows, among other things, the current product recalls for children’s shoes.

POLOLOs only made of vegetable tanned leathers – without Polyurethane and chemical finishes

For the aforementioned reasons, POLOLO relies on safe products that are also suitable for allergy sufferers and uses only vegetable-tanned leathers.
Kuntze showed Valonea acorns as an example of a vegetable tanning agent and green chrome in powder form as an example of a mineral tanning agent. Chrome-tanned leathers are grey-green and thus always require subsequent dyeing.

Chemical finishing of leather

Another important aspect is the renunciation of further chemical finishing of the leather. After all, there is no such thing as a flawless surface without natural characteristics in leather – just as there is no such thing in humans, where the skin can have mosquito bites, pigment changes or injuries. Even under excellent husbandry conditions, cattle sustain minor injuries during their lives, which are reflected on the surface of the leather. In conventional production, however, a completely uniform surface appearance of leather without any natural features is important in order to optimise the leather waste. For this purpose, coated or covered leathers are used. Coating or finishing the leather equalises the leather surface. Synthetic materials are used which, once applied, form an even and uniform surface. The process is supported by colour pigments that cover colour differences. After the coating, the leather is usually embossed. This gives the surface a leather-like texture again, but on closer inspection it can look artificial because the natural features and irregularities are missing.
What looks flawless is chemically tricky. The plastics, including polyurethane, acrylic lacquers, halogenated hydrocarbons, vinyl compounds, organic hydrocarbons such as butadiene, harbour health risks. The warnings for the substances used range from allergy triggering to suspected health risks. In addition, the finishing of the leather changes its use properties. On the one hand, the leather becomes insensitive to dirt and water-repellent because the skin pores are closed by the coating. On the other hand, however, this also cuts off the exchange of air between the leather fabric and the environment. This is how leather got its reputation of being a cold material. However, this only applies to coated leather. Natural leather is in exchange with the ambient air and is therefore always at a pleasant temperature.

POLOLO Screenshot: Franziska Kuntze introduced the topic of natural leather