I have been running a range of tests on wool versus synthetic fabrics to help me understand relative performance with a bit of hard data. Whilst insulation has been the main focus of my tests so far, performance when wet is also a key consideration. Whether mountaineering, hiking or bushcrafting it is rare for it to stay totally dry so moisture management is key to getting the best out of a clothing system.
There are a few main aspects related to effective performance and water:
- Does the fabric keep you warm when wet?
- Does it dry quickly?
This test looks at the latter. How does Merino wool stack up in drying times versus that staple of synthetic outdoor fabrics, for base layers or other kit, polyester.
How to reliably test drying times?
Many tests for drying times rely on the garment feeling dry. To some extent this is important, we are wearing the garment after all, however to take a slightly less subjective approach I have chosen to weight the garments to gauge how much moisture they still contain. The first garment to get within 5% of it’s dry weight is the winner.
In the test I am using two base layer garments of very similar weight and use. Namely a pair of 100% merino Howies long johns/ leggings, weighing in at 161g and a pair of decathlon polyester long johns weighing in at 167g. Both ideal for cold weather insulation. But which one would be the go to for those trips where they may get wet and need drying out?
The garments were both fully immersed in a bucket of water and squeezed for a minute to ensure good saturation. Then the saturated garments were wrung for 30 seconds to remove most excess moisture and weighed. Following this they were hung to dry and weighed at intervals to determine how dry they were.
The results
As the following graph shows the synthetics did take the win however there were a few surprises and interesting insights to draw from the results. Overall the synthetics reached the target dry weight, defined as within 5% of start weight, around half an hour before the merino. Time itsellf is fairly meaningless, as this is massively influenced by conditions, so it is perhaps more useful to define the outcome as the synthetic garment dried about 10% faster than the merino wool.
Surprise #1 – The synthetic took on more water initially than the wool
As synthetic fibres do not absorb water, whereas wool does, I really didn’t expect this, however weighing in the saturated garments revealed the synthetic garment to be holding on to more water than the wool. I tried to be as fair as possible in the wringing process, although this is hard to replicate precisely, but in any case the merino wool seemed to float and not readily absorb water initially. My theory on this is that wool with a rougher structure and inherent fluffyness holds small air bubbles/ pockets, readily.
Surprise #2 – How much water the fabrics actually held
If you asked me to say how much water a saturated garment that had been wrung would weigh I might have said double, however with most loose water removed I was really suprised to see this closer to triple.
Surpise #3 – The win for synthetics was narrower than expected
It was no great suprise that the synthetic garment did reach “dry” before the wool garment, however I was suprised how close the battle was. Over the course of 5-6 hours it was in the region of 10% faster to dry. In practice in the field this probably doesn’t mean that the superior drying time of synthetic itself is strong enough a reason to choose synthic over merino for many circumstances.
So which baselayer to choose – Merino vs. Synthetic
Overall despite a narrow loss on drying times there was not a big enough difference to make me change my base layer choices for different circumstances. However it has consolidated my thinking slightly. If I could choose only one base layer type it would be Merino for all round performance and environmental reasons. However the synthetic still has a place and a younger poorer me relied on synthetics quite happily for years.
Merino – Still perfect for longer trips and colder weather where optimal performance is key. For longer trips, or trips in colder weather I prefer merino and will continue to make that choice. I am pretty reassured by the fact that merino actually does dry nearly as well as the synthetics. Allied to the fact that wool is said to maintain its insulative value whilst holding 30% of it’s weight in water the slightly slower drying time is not a big issue for me.
Synthetic – Short and damp trips in milder conditions. Synthetics remain strong all round performers and have a minor edge on drying time. For short trips in warmer conditions and those where some damp is almost a certainty, e.g. canoeing, or rainy summer conditions I will continue to roll out the synthetics I already own.