Effective leather grading
Describing the SATRA system designed to accurately assess the usability of leather.
by Lee Lythgoe
As a natural product, leather has been the cause of many differences of opinion over the years, and calculating the ‘usability’ of leather has long been an emotive subject for both supplier and user. A traditional procedure for calculating leather’s usability was for the assessor to select a random sample of incoming leather (usually 10 per cent) and to physically mark any areas that were considered to be unusable. These were measured, and the total unusable area expressed as a percentage of the overall area assessed. This single figure was then assumed to be representative for the entire delivery. However, in many areas, the sample could be very unrepresentative of the entire delivery, with resultant disagreements between leather user and leather supplier.
It is essential for all leather users – especially footwear manufacturers – to have a reliable and realistic input into the calculation program to represent the perceived usability of leather. SATRA has developed a unique approach to establishing the usability of leather in the footwear, leathergoods, furniture and automotive industries. The basic principle is simple – that the supplier of the leather and the end user agree on a method of labelling leather as defined by one selected product. To that end, in the case of footwear, a men’s inside quarter pattern is agreed upon as the standard tool to use to grade the leather.
The SATRA grading system
The SATRA system is known as the ‘5 point grading system’. This requires that every skin in the delivery is visually inspected and assigned to one of a number of pre-determined bands of usability. Each band represents a spread of 5 percentage points as shown in box 1.
|Box 1: Pre-determined bands of usability in SATRA’s 5 point grading system|
|Band/grade||5 point spread (per cent)||Defined midpoint (per cent)|
SATRA’s consultants visit the member’s company and train up to eight quality control personnel. This usually takes three days, or, two groups of eight people in five days. This training covers three aspects:
- Ensuring that there is an agreed quality standard within the user company. This must be documented and available for reference
- Teaching the Quality Control (QC) personnel to assess the leather correctly according to the agreed standard
- Establishing a recording system for the essential management information, including batch traceability.
A second visit to the company will be necessary to establish the competence of the application. During this visit, a different SATRA consultant will check to ensure the following:
- That individual QC personnel can achieve a 95 per cent correlation between their assessments and the required standard
- That management of the information is to the required standard.
Individual QC personnel will be certified if they meet the criteria, and the company itself will receive accreditation provided that it is a member of SATRA and that it employs at least one SATRA-trained QC consultant. The SATRA-trained QC personnel can, in turn, train other assessors and these can also be certified after proving their capability. The accreditation will last for one year, with renewals requiring the same level of compliance as before.
Use of the SATRA 5 point leather grading protocol has significant benefits:
- Agreed standards with suppliers (both supplier and user can agree standards together)
- More accurate specification for purchasing
- Accurate comparison of prices from different suppliers
- Reliable standard against which to check suitable materials are supplied. Agreed standards are signed and dated by supplier and user and can be used in case of dispute
- Appropriate use (match skins to product)
- Cost effectiveness.
SATRA has also found that users gain around 3 per cent more usable leather, as all skins are matched with relevant product models.
How can we help?
Please contact email@example.com for more information on the SATRA 5 point leather grading system.
This article was originally published on page 12 of the July/August 2011 issue of SATRA Bulletin.