CEN/TC 289 - Leather

This document provides lists of chemicals that have already been detected in leather and guidelines for applying the available chemical test methods for leather. This information can be used by those involved in setting specifications for leather, especially for those parameters relating to restricted chemical substances.
Generic lists of restricted chemicals used on the market contain many substances that are not relevant to the leather industry. Those chemical substances that are not mentioned in this document do not need to be determined, thus avoiding unnecessary analytical costs.
NOTE            Due to the constantly changing legal requirements and toxicological evaluation of chemical substances, this document cannot address all potentially critical substances.

This document defines the requirements that are necessary to confer the origin of leather production based on the principle of the last substantial transformation according to Non-Preferential Rules of Origin.
This document is applicable to leather only and it is applicable also to leather with hair. Furs are excluded.
The country of origin of raw hides and skins isn’t relevant for the application of this document.

This document specifies average values of leather density, depending on animal origin and thickness of finished leather, to be used for the calculation of LCA. This document is applicable to bovine, caprine and ovine types of leather.
This document does not apply to vegetable sole leather which is traded by weight.

This document specifies a method for determining the total content (solvent extractible) of the following bisphenols in leather:
—     bisphenol A;
—     bisphenol B;
—     bisphenol F;
—     bisphenol S.
This method requires the use of liquid chromatography (LC) with either a single quadrupole mass spectrometer (MS), a triple quadrupole mass spectrometer (MS/MS), an ultraviolet (UV) detector, a diode array detector (DAD) or a fluorescence detector (FLD) to identify and quantify the bisphenols.
NOTE            This method can also be used for other bisphenols if they are validated by the laboratory.

This document specifies a test method for detection and quantification of extractable non-volatile per- and polyfluoroalkyl substances (PFAS) in leather and coated leather by solvent extraction and liquid chromatography coupled with mass spectrometry.
This document, taking into account the three-dimensional distribution of the fibres within leather, makes the evaluation of the PFAS with respect to the mass.
PFAS substances categories and applications are listed in Annex A, Table A.1. Classes of PFAS regulated compounds listed in Annex B, Table B.1, include acids, telomers, sulfonates and sulphonamide alcohols. Classes of other non-regulated compounds that can be determined by this document are listed in Annex C, Table C.1.
NOTE 1        By applying the method specified in this document, the concentration of free fluorotelomer alcohols (FTOH) in a sample cannot be correctly quantified if perfluoropolymers that release FTOH due to transesterification with the extraction solvent methanol are present in the sample.
NOTE 2        Some regulations (e.g. Reference [4]) also restrict perfluoropolymers having a linear or branched perfluoroheptyl group with the moiety (C7F15)C as one of the structural elements that can degrade to PFOA, e.g. polymers containing 2-perfluorooctylethanol (8:2 FTOH, CAS Registry Number® 678-39-7) bonded as esters. To determine whether these perfluoropolymers are intentionally present, it could be necessary to introduce an alkaline hydrolysis method to remove the 8:2 FTOH side-chain from the polymer. In addition, other FTOH, e.g. 6:2 FTOH or 10:2 FTOH, will be released from relevant perfluoropolymers by alkaline hydrolysis.

This document is a method for determining ethoxylated alkylphenols (APEO) [nonyphenol ethoxylate (NPEOn, where 2 ≤ n ≤ 16) and octylphenol ethoxylate (OPEOn, where 2 ≤ n ≤ 16)] in leather. This direct method is especially suitable when a larger number of leather samples are to be checked for the presence of ethoxylated alkylphenols.
This method requires the use of liquid chromatography (LC) with a triple quadrupole mass spectrometer (MS/MS) to identify and quantify the ethoxylated alkylphenols.
NOTE 1        In the leather industry, the most commonly used ethoxylated alkylphenol is the NPEO, with an average of 9 EO. It has an optimum cloud point in water for the typical leather processing temperatures of 40 °C to 55 °C.
NOTE 2        This document and ISO 18218-2 use different solvents for the extraction of the ethoxylated alkylphenols from leather. Consequently, the two analytical methods are expected to give similar trends but not necessarily the same absolute result for the ethoxylated alkylphenol content in leather.

This guideline provides a list of recommended tests that can be used to assess the quality of chemicals used in tanning process.
This guideline applies to chemicals whose application has the same effect on leather, grouped in families.

This document specifies the position of laboratory test specimens within a piece of leather and the method of labelling and marking the laboratory test specimens for future identification. In addition, this document specifies the design of press knives for cutting test pieces and the preparation of test pieces.
It is applicable to all types of leather derived from mammals, irrespective of the tanning used.
It is not applicable to leathers derived from birds, fish, reptiles or furs.

This document describes a method for determining the water vapour permeability of leather and provides alternative methods of sample preparation and for the measurement procedure.

This document provides a method for the measurement of the surface of leather or leather parts by the use of electronic measuring machines.
It applies to the measurement of leather (or leather parts) fulfilling the following requirements:
—    flexible leather, finished or unfinished dry leather;
—    flexible wet leather (see Annex E);
—    flexibility, such as to allow full distension on the measuring line or surface.

This document gives guidelines for the test methods and recommended values for upholstery leather for furniture.
This document also specifies the sampling and conditioning procedures of specimens.
Furs, hair-on leathers and wool-on leathers are not covered by this document.

This document sets the requirements for the description, labelling and marking of leather in leather goods.
This document defines the information to be included on descriptions, labels and markings for leather goods intended for sale to the final consumer.

This document specifies requirements for the designations and descriptions used in the exchange of goods when exhibiting, promoting (e.g. advertising and labelling), and placing on the market when leather is used in automotive interiors.
This document provides general guidelines intended to be applied in the designation and description of automotive seating and interiors when reference is made to leather as a constituent material.
The designation or description of leather used in upholstered furniture, leather in footwear, leather goods and leather clothing including gloves are not covered by this document.

This document specifies requirements for the designations and descriptions used in the exchange of goods when exhibiting, promoting (e.g., advertising and labelling), and placing on the market when leather is used in upholstered furniture.
Parts of furniture with appearance that does not correspond to leather (e. g. wood, metal) and parts of purely decorative nature are not covered by this document.
The designation and/or description of leather in footwear, leather goods and leather clothing including gloves are not covered by this document.
The designation and/or description of leather in automotive interior applications is covered in EN 16223 2.

This document specifies general principles on colour fastness evaluation tests for leather, as listed in Annex A.
Procedures included in this document are common to most of the fastness test methods.
This document provides a common basis for testing and reporting colour fastness. The uses and limitations of the methods are pointed out, several terms are defined, an outline of the drafting of the methods is given and the contents of the clauses describing the methods are discussed.
Procedures common to a number of the methods are discussed briefly.
Colour fastness means the resistance of the colour to the different agents to which these materials can be exposed during manufacture and their subsequent use.
The change in colour of leather and staining of undyed adjacent fabrics or other materials are assessed as fastness ratings.
Other visible changes in the leather under test, for example surface appearance, change in gloss or shrinkage, are considered as separate properties and reported as such.
The leather fastness test methods can be used not only for assessing leather and related materials, such as coated leather and leather board, but also for the eventual assessment of the colour fastness of leather dyes. When such a method is so used, the dye is applied to a specified retanned leather or crust leather in defined depths of colour by stated procedures and the material is then tested in the usual way.

This document specifies a method for measuring the adhesion of the finish to leather or the adhesion between two adjacent layers of the finish.
The method is valid for all finished flexible leathers with a smooth surface that can be bonded to an adherent plate without the adhesive penetrating into the finish. Preliminary experiments can be necessary to determine whether these conditions are met.
This test method applies to finished leathers with a thick finish-coat.
The method specified in this document does not apply to unpigmented articles or articles without a continuous coating layer, such as:
—    nubuk;
—    aniline;
—    pull-up;
—    suede;
—    perforated leather.

This document specifies a method for determining the dry or wet flex resistance of leather and finishes applied to leather. It is applicable to all types of flexible leather below 3,0 mm in thickness.

This document specifies the key terms and definitions used for the leather trade and provides guidance on the correct use of the term “leather”.
Defined parameters in this document need to be assessed using standard test methods specific for leather.
NOTE   See Bibliography for leather test method standards.

This document specifies a test method for the determination of the bending force of leather.

This document specifies a method for the determination of the total metal content in leather using digestion of the leather and subsequent determination with inductively coupled plasma optical emission spectrometry (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS), atomic absorption spectrometry (AAS) or spectrometry of atomic fluorescence (SFA).
This method determines the total metal content in leather. It is not compound-specific or specific to the oxidation state of the metals.

This document specifies a method for assessing the propensity of dyes and pigments to migrate from leather to a synthetic substrate by determining the transfer of colour from the leather to white polymeric material in contact with it.
This method is applicable to leather of all kinds at any stage of processing.

This document specifies a thermal pre-ageing procedure for leather to obtain indications about the tendency to the formation of hexavalent chromium under specified conditions and the determination of hexavalent chromium according to ISO 17075‑1 or ISO 17075‑2.
This thermal pre-ageing procedure does not simulate any real condition in leather production or use.
It is applicable to all types of chromium tanned leather.

This document specifies a quantitative test method to determine 24 kinds of pesticide residues in leather by gas chromatography-mass spectrometry (GC-MS).
This document is applicable to all types of leather that could release pesticides.

This document specifies a chromatographic method to determine the amount of middle-chain chlorinated paraffins (MCCPs) C14 to C17 in processed and unprocessed leathers.

This document specifies a chromatographic method to determine the amount of short-chain chlorinated paraffins (SCCPs) C10 to C13 in processed and unprocessed leathers.

This document gives recommended values and related test methods for apparel leather, excluding furs. It also specifies the sampling and conditioning procedures of laboratory samples.

This document specifies a method of determining the dimensional change (shrinkage) of leathers caused by ageing. It is applicable to all leathers.

This document specifies a method for the determination of free formaldehyde, which is released under dynamic conditions when the sample is heated in an inert dry atmosphere, in process auxiliaries for leather. The analytical result obtained according to this procedure is expressed in milligrams per kilogram (mg/kg) sample.

This document specifies a method for the determination of free and released formaldehyde in leathers. This method, based on high-performance liquid chromatography (HPLC), is selective and not sensitive to coloured extracts and is intended to be used for precise quantification of formaldehyde.
The formaldehyde content is taken to be the quantity of free formaldehyde and formaldehyde extracted through hydrolysis contained in a water extract from the leather under standard conditions of use.

This document specifies a method for determining the use of certain azo colourants which can release certain aromatic amines.

This document specifies a test method by acetonitrile solvent extraction for the determination of the total content (solvent extractible) of the following preservative agents in leather by liquid chromatography:
—     2-(thiocyanomethylthio)-benzothiazole (TCMTB);
—     4-chloro-3-methylphenol (PCMC);
—     2-phenylphenol (OPP);
—     2-octylisothiazol-3(2H)-one (OIT);
This method can also be used to determine breakdown products of these preservative agents, which protect leather from microbiological attack.

This document specifies a test method by artificial perspiration solution aqueous extraction for the determination of the aqueous extractable content of the following preservative agents in leather by liquid chromatography:
—     2-(thiocyanomethylthio)-benzothiazole (TCMTB);
—     4-chloro-3-methylphenol (PCMC);
—     2-phenylphenol (OPP);
—     2-octylisothiazol-3(2H)-one (OIT);
This method can also be used to determine breakdown products of these preservative agents, which protect leather from microbiological attack.

This document specifies a test method to determine the degree and rate of aerobic biodegradation of hides and skins of different animal origin, whether they are tanned or not, through the indirect determination of CO2 produced by the degradation of collagen.
The test material is exposed to an inoculum (activated sludge from tannery wastewater) in an aqueous medium. If there is not a tannery nearby then urban wastewater can be used as the inoculum.
The conditions established in this document correspond to optimum laboratory conditions to achieve the maximum level of biodegradation. However, they might not necessarily correspond to the optimum conditions or maximum level of biodegradation in the natural medium.
In general, the experimental procedure covers the determination of the degradation degree and rate of the material under controlled conditions, which allows the analysis of the evolved carbon dioxide produced throughout the test. For this purpose, the testing equipment complies with strict requirements with regard to flow, temperature and agitation control.
This method applies to the following materials:
—     natural polymers of animal stroma (animal tissue/skins);
—     animal hides and skins tanned (leather) using organic or inorganic tanning agents;
—     leathers that, under testing conditions, do not inhibit the activity of microorganisms present in the inoculum.

This document specifies a method for determining the tensile strength, elongation at a specified load and elongation at maximum force of leather. It is applicable to all types of leather.

This document specifies a method using microscopy to identify leather and distinguish it from other materials. The method is not applicable for identifying specific leathers (e.g. sheep leather).

This document specifies a test method for the determination of tanning agents through filtration of all vegetable and synthetic tanning products.

This document specifies a method of determining the abrasion resistance of leather using a Taber® apparatus.

This document specifies a method for determining alkylphenols (nonylphenol and octylphenol) and alkylphenol ethoxylates (nonylphenol ethoxylate and octylphenol ethoxylate) in leather and process auxiliaries. The analysis is based on high-performance liquid chromatography (HPLC) or gas chromatography-mass spectrometry (GC-MS).
The analysis of the alkylphenol ethoxylate is made by cleaving the alkylphenol ethoxylate and measuring the released alkylphenol.
NOTE       ISO 18218-1 and this document use different solvents for the extraction of the ethoxylated alkylphenols from leather. Consequently, the two analytical methods are expected to give similar trends but not necessarily the same absolute result for the ethoxylated alkylphenol content in leather.

This document specifies a method for determining the stitch tear resistance of leather. It can be used on all leathers but is particularly suitable for leathers over 1,2 mm in thickness.

This document specifies a method for the correct measurement of the colour of finished leather by instrumental means. The document describes general concepts of colour measurement adapted to leather and the calculation of differences in colour.
This document defines the following:
a)    the use of D65 as the standard light source for the leather industry;
b)    the use of D65 light source 10° as standard conditions for colour matching, for the definition of daylight simulators and as the reference light source for metamerism analysis;
c)    the use of CIEDE2000 as the colour difference formula.

This document specifies a method for determining the resistance of all forms of leather to visible soiling through repeated contact with soiled objects. It provides a physical pretreatment routine for leathers that may be vulnerable to loss of soiling resistance while in service, prior to conducting further tests such as cleaning.

This document specifies a method for the determination of extractable metals in leather using extraction with an acid artificial-perspiration solution and subsequent determination with inductively coupled plasma optical emission spectrometry (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS), atomic absorption spectrometry (AAS) or spectrometry of atomic fluorescence (SFA).
This method determines extractable metals in leather; it is not compound-specific or specific to the oxidation state of the metals. This method is especially suitable for determining the extractable chromium in chromium-tanned leathers.

This document describes a method for the determination of chromium in aqueous solution obtained from leather. This is an analysis for total chromium in leather; it is not compound specific or specific to its oxidation state.
This method describes the determination of chromium by inductively coupled plasma (ICP) and is applicable to leathers which are expected to have chromic oxide contents in excess of 1 mg/kg. Two techniques for the preparation of the solution to be analysed are included. In the event of dispute, the wet oxidation technique is intended to be used.

This document specifies a method for the determination of free and released formaldehyde in leathers. This method, based on colorimetric analysis, is not intended to be used for a precise quantification of formaldehyde.
The formaldehyde content is taken to be the quantity of free-formaldehyde and formaldehyde extracted through hydrolysis contained in a water extract from the leather under standard conditions.
This process is not absolutely selective for formaldehyde. Other compounds such as extracted dyes could interfere at 412 nm.

This document specifies a method for determining the behaviour of the surface of a leather on rubbing with a wool felt.
It is applicable to leathers of all kinds.

This document specifies a method for the determination of the substances in leather which are soluble in dichloromethane. This method is applicable to all types of leather.
Not all fatty and similar substances can be extracted from leather with organic solvents; they may be in part soluble and partly bound to the leather. On the other hand, the solvent can dissolve non-fatty substances, for example sulfur and impregnants, both of which cause difficulty in the determination of the acid value and saponification value of the fat.
This document includes two techniques for extraction of the fatty substances: 1) extraction using the Soxhlet apparatus; and 2) extraction using a pressurized extraction system.
As the extraction is frequently done in conjunction with determination of the free fatty acid content of the leather, a suitable procedure for determination of the free fatty acids extracted by this method is included.
The apparatus and technique described in this method are also suitable for the extraction by solvents other than dichloromethane (although the temperature conditions may need to be varied for high pressure extraction).

This document describes a method for the determination of chromium in aqueous solution obtained from leather. This is an analysis for total chromium in leather; it is not compound specific or specific to its oxidation state.
This method describes the determination of chromium by atomic absorption spectrometry and is applicable to leathers which are expected to have chromic oxide contents in excess of 5 mg/kg. Two techniques for the preparation of the solution to be analysed are included. In the case of disputes, the wet oxidation technique is to be used.

This document describes a method for the determination of chromium in aqueous solution obtained from leather. This is an analysis for total chromium in leather; it is not compound specific or specific to its oxidation state.
This method describes the determination of chrome by iodometric titration and is to be applicable to chromium-tanned leathers which are expected to have chromic oxide contents in excess of 0,3 %. Two different methods are described as alternatives for obtaining chromium in a suitable solution. It is appropriate to use either method.

ISO 4098 | IULTCS/IUC 6:2018 specifies a method of determination of water-soluble matter, water-soluble inorganic matter and water-soluble organic matter.
ISO 4098 | IULTCS/IUC 6:2018 is applicable to all leather types. The result obtained by this analysis depends on factors such as:
-      the degree to which the leather is ground;
-      the extraction temperature;
-      the extraction period;
-      the ratio of leather to water.
To obtain comparable results, it is consequently imperative that test conditions be accurately reproduced.
In all cases, any ammonium salts in the filtrate are included as part of the water-soluble matter and are then decomposed on ignition. Thus they contribute towards the result for water-soluble organic substances. The concentration of the ammonium salts can be determined in the filtrate separately if required.

This document specifies a method for determining the pH value and the difference figure of an aqueous leather extract. It is applicable to all types of leather.