ISO 9865, the determination of water repellency of fabrics by the Bundesmann tester, was first introduced in 1991 and last reviewed in 2016 - you can purchase the standard here. It has grown in popularity in recent years, as the performance of outdoor wear has become more important to brands and consumers.

The standard specifies the use of a Bundesmann, and James Heal's TruRain is a modern, user friendly version of this instrument. The actual test takes 10 minutes, but the instrument must be primed and specimens conditioned before the test starts. The test specimen must be weighed prior to testing, to an accuracy off 0.01g – this measurement will be used to calculate water absorption once the test is finished.

This test measures three aspects of water repellency:

graded assessment on trurain Bundesmann tester


Surface water repellency is assessed by visually comparing the tested specimen with a photographic grading scale (similar to the spray rating tester).

This assessment should be conducted while the specimen is still on the cup, immediately after testing.

The standard gives the option to do this assessment at 1 minute and 5 minutes into the test as well, and although these steps aren’t necessary, they can be useful for spotting early issues with the fabric.

TruRain specimen on a centrifuge


Resistance to water absorption is evaluated by weighing the specimen before and after the test. The after test measurement is taken after the specimen has been centrifuged to remove any excess water.

It is important to remove the excess surface water because this step of measurement is concerned only with the water that has been absorbed by the fabric, so weighing surface water as well would misrepresent the measurement.

The results for water absorption are worked out using a formula as stated in the standard and expressed as a percentage.

Water beaker and measuring tube


Resistance to water penetration is determined by collecting and recording any water which passes through the test specimen into the specimen holder cups.

Choosing the right measuring vessel for this step is important -  the standard asks you to measure the volume in millilitres and for the best fabrics this could be a very small amount of liquid. Using a large measuring beaker could make this process difficult, if you have enough specimen fabric and time, it might be worth doing a test run to work out which equipment will suit you best.

lab technician touches the screen to set a test

Setting the standard

Our instruments are pre-programmed for this standard - meaning you don't have to lift a finger.

Talk to our test engineers today for help configuring your instrument according to your standard.