The Mud / Boot Interface
By Richard Welch
This timely article is the second of an occasional series concerning mud. It examines the mud / boot interface (MBI) and the strategies employed in footwear maintenance (what we scientists call “getting the mud off your boots”).
Before facing the business of removing the mud, how does the mud get there, and why does it stick? Initially, field studies were carried out, but the scientists quickly tired of cleaning the mud off their own boots, and so extensive laboratory tests were performed with volunteers (who had to clean the boots).
High speed photography revealed that only when mud is agitated does it home in on the nearest boot. A descending boot displaces mud in all directions, but mostly sideways and upwards. Mud that has been displaced upwards can fall back on top of a nearby boot depending on it’s proximity and the complexities of mud splatter dynamics (a subject which will be dealt with in a future article). Mud which has been displaced sideways moves back into contact with the boot due to the effects of surface tension and gravity. Mud with a water content of less than 17% can show an elastic response, which means that it rebounds towards the boot, but this is a minor phenomenon which need not concern us here (thank goodness, I hear you cry).
As to the question of why mud sticks to boots so well, there is an MBI theory that wet clay particles are able to penetrate the surface pores of the leather, and form a semi-crystalline layer of great strength. Back in 1970 three Israeli scientists working in London (Marks, Spencer Et Al) undertook some pioneering work to discover the secret of the mud/boot interface. Under a magnifying glass, samples of mud appeared perfectly normal – some embedded sand, lead shot, a contact lens and an aluminium ring-pull. Next they tried the scanning electron microscope and discovered various ugly micro-organisms, traces of crude oil and a micro-dot of a Japanese conglomerate’s plan to buy the Isle of Wight. Again, nothing unusual. There is obviously much more research to be done, before mud’s stickability is explained.
Since there are variations in the types of boot construction and the leathers used, different boots will withstand different degrees of neglect before they expire! Very dry leather is prone to cracking, so if you know your boots will not be cleaned for a few days put them in a plastic bag. It’s easier to remove mud before it dries rock hard. Running water is very useful if you are fastidious, but has a habit of creeping up the wrist! Take my tip and don’t remove every trace of mud. There is an old saying: “He who appears on a ramble wearing pristine boots will surely be pushed into the first puddle”.
Copyright (c) 2009 St. Albans Adventure Group. This article was first published in the group magazine Stagger in April 1989.