If you’re a fan of visiting museums that showcase the vehicles, weapons, clothes, and everything that people used during the times of war, like the National WWII Museum in New Orleans, then you might have noticed that some of the German tanks have this strange-looking texture that covers the vehicles’ surfaces. You might have assumed that these textures were part of the camouflage, but in fact, it was some sort of anti-mine idea that they added so that magnetic mines would not stick to their armored vehicles, called Zimmerit. While it could’ve been quite a brilliant idea, it was, in fact, unnecessary.
When looking at German tanks from WWII, you may have noticed a strange texture covering most surfaces of their armor. Although this looks like an interesting type of camouflage, it’s actually a special coating devised by the Germans to decrease the magnetic properties of a tank’s armor and decrease a magnetic mine’s ability to stick to it. Named Zimmerit, the coating was difficult and time-consuming to apply. It ultimately proved unnecessary, as ironically, Germany was the only combatant in WWII to field magnetic mines in any appreciable amount.
In 1942, Germany released their perhaps most famous magnetic anti-tank magnetic mine called the Hafthohlladung, or handheld hollow charge. It used three strong horseshoe-shaped magnetic feet made of Alnico-type alloy to stick to the armor of the enemy vehicle. It had an adhesion strength of 6.8 kg-equivalent.
The magnetic mines came in different sizes, although the most common weight was 6.6 pounds or 3 kilograms. Each Hafthohlladung contained a 1.5 kilogram shaped charge made of PETN/Wax. It was pretty straightforward how to use it: grab the mine and run-up to the target tank, stick it on any magnetic surface of the vehicle, pull the safety pin, and run for your life. The magnets were there to ensure that the device was properly distanced from the armor and that it would cause the desired damages.
While the magnetic device pretty much removed whatever advantages armor angling gave, it also imposed risks on the soldiers assigned to do the task. It exposed them not only to the enemy fire whenever they approached the vehicle but also to the defenses of the tank itself.
The idea of Zimmerit came into the picture when the Germans feared that the Allies would use the same magnetic mine concept against them, and so they started with the countermeasures even before it happened. The idea was to add a physical barrier between the armor and the mine so that it would not stick, using the principle of magnetostatic fields decreasing quickly as they go farther. According to Tank Museum, here’s what Zimmerit was made of,
pine crystals dissolved in benzene, zinc sulphide, barium sulphate, pine saw dust, PVA glue, pebble dust and ochre. When mixed correctly the result was a sticky soft putty. It was applied with a trowel to particular areas of the vehicle according to specific instructions. Coating a Tiger I required 200kg, a Panzer IV half that.
While it did not at all make the tank entirely anti-magnetic, the Zimmerit coating reduced the sticking ability of the mines’ magnets. These were only applied to the areas of the tank that soldiers on foot could reach. Beginning in August 1943, vehicle factories started coating the vehicles with the mixture. The workers would blowtorch the Zimmerit to quickly burn off excess moisture to speed up the process, with the excess benzene bursting into flames in the process. While it was hazardous, the workers still opted to do that as Zimmerit took eight days to dry on its own.
The patterns of the coating varied depending on which factory applied it, although the most common one was ridging, and then for some vehicles, the waffle pattern, as seen on the StuG-III.
Rumors began circulating within the German camps that Zimmerit could catch on fire once incoming grounds hit the coating. The Germans tested it and proved that it was not true. Regardless, the coating was never used again. Germans were in desperate need of tanks, and having that additional step would consume more manpower, resources, and time, that they didn’t all have the luxury of at that time.
Perhaps the biggest reason why they completely discontinued was that, as it turned out, the Allies never used magnetic mines on a large scale as the Germans imagined, so the Zimmerit coatings were not necessary in the very first place.