There is not a Martindale Shade Change test as such.
You have probably been referred to the Martindale Rub test by someone looking to know how durable your chosen fabric is to abrasion. the Martindale rub test result is particularly useful in indicating if your chosen fabric is suitable for the intended use. An indispensible indicator for interior designers.
The Shade Change is something different. Martindale tests are routinely undertaken on fabrics especially in the UK. In other countries there are different tests like the Wyzenbeek in the USA. However it is becoming more common in the UK that as part of the Martindale test a Shade Change test is also undertaken.
When a fabric has been ‘rubbed’ by a machine 3,000 times the Martindale test is paused and the fabric is examined to see how the shade of the fabric has changed. It is then given a mark out of 5 with 5 being the best result (least change).
A natural property of fabrics is that they wear with use. I guess one way of looking at the shade change test is to determine how much of that wear will be visible after a reasonable amount of use. With 3,000 rubs being classed as reasonable. It does not mean that your fabric will wear out after 3000 rubs, it has nothing to do with wearing out!
If your fabric has a Martindale result of 50,000 rubs this means that the structure of the fabric starts to break down after 50,000 rubs. Essentially the ‘rubs’ simulate to varying degrees how people will sit down repeatedly.