Why a test result does not last forever

Short answer: Because it applies to the sample that was tested, from the batch it came from. The next batch is made from new yarn, in a new dye bath and perhaps on another machine.

The test applies to the tested sample

A test result is a snapshot. It says something about the sample the laboratory received, and nothing about all the other garments later made from the same model. That sounds like a small difference, but it is decisive when you judge what a report can actually be used for.

The sample comes from one batch

The sample comes from one particular batch, and the batch has its own history of yarn, dye and machines. The report documents that this batch met the requirements tested for. It does not say the next batch will do the same, unless that one has also been tested and given a result.

Raw material changes between batches

Cotton and wood pulp vary from harvest to harvest and from supplier to supplier. That shows in the yarn, which can be slightly coarser, finer or glossier from one time to the next. Even if supplier and quality are the same on paper, the raw material can behave a little differently in the next batch.

The yarn carries the difference on

The yarn passes the difference on to the fabric, and the fabric passes it on to the finished garment. Small swings in the yarn can give small swings in how the fabric shrinks, feels or takes colour. So testing the yarn once is not enough to assume everything after it looks the same.

The process is never quite the same

The process is never quite the same. Temperature, time and water quality vary a little from one run to the next, and that gives small differences in the finished fabric. They are usually small, but enough that a result which only just met a requirement once may miss it next time. See also the Decoy collection.

The dye bath varies

The dye bath is a good example. Even with the same recipe, a new bath can give a different shade or a different colour fastness from the last one. That is why colour fastness is often tested on each batch separately and not just once for the whole model. It is a simple way to catch small swings early.

That is why testing is repeated

For new batches of the same product, new samples are taken, especially when something in the chain has changed. That could be a new yarn supplier, a new dye house or another machine. The more has changed, the more important it is to test again. See also Urban Quest and Jack and Jones.

What a report can still be used for

An older report is not useless. It shows that the product can be made within the requirements, and it is still a good sign that the producer knows the craft. You simply have to read it for what it is, a result for one batch, and not as a guarantee for all the batches that follow.

What you can do as a customer

As a customer, you can use reports as a guide but not as a promise. Ask when the test was done and whether it applies to the batch you receive. If you are unsure, check the item yourself when it arrives, and contact customer service if anything differs from what you expected.

Frequently asked questions

Does that mean the report is useless

No. It shows the product can be made within the requirements, and it applies to its own batch. It should just not be read as a guarantee for every later batch.