File No.: Battle Relic # 29
Title: "Zimmerit"
Investigation made at: An undisclosed location in the Netherlands
Period Covered: 1942 - SEP 1944
Date: NOV 2011 to JAN 2017
Case Classification: Study of a chemical component named “Zimmerit” which in Nazi Germany was used to create a non-magnetic layer on armored vehicles against magnet-borne anti –tank shape charges. Recreation of Zimmerit and testing its (non-)magnetic and (in-)flammable properties.
Case Status: Case Closed
REASON FOR INVESTIGATION: In an abundance of publications the substance “Zimmerit” is described. This non-magnetic anti magnetic charge substance was only used by Nazi Germany; not by its enemies. It gave a very distinctive look to their weaponry. It is this agency's intention to learn if Zimmerit was in fact non-magnetic and of it would ignite.

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Applying recreated Zimmerit
on an original World War Two
Nazi tank part

1926 commercial logo of Zimmerit
corrosion protective coating

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Zimmerit coating on Third Reich tanks
(Note a rare case of Zimmerit applied on Königstiger mudguards in the last image)

   
Period images of the use of the Hafthohlladung

Ingredients
Zimmerit was made up of the following:
40% Barium Sulphate, BaSO4 - is made from Barium (Ba) treated with Sulpheric acid (H2SO4), and is water-insoluble
25% Polyvinyl Acetate, PVA - commonly known as white carpenters glue
15% ochre pigment,  An earth-toned coloring material
10% Zinc sulphide and ZnS - a natural mineral, and a Zinc ore.
70% Zinc Sulphide and 30% Barium Suphate give Lithopone, a white pigment
10% sawdust

The application of Zimmerit on armor

Two leading sources for purpose and ingredients of Zimmerit
1) Post-war interview with chief engineer Robert Pertuss of the Henschel tank manufacturing company in Kassel, Germany.
2) British Intelligence Objectives Sub- Committee report "Zimmerit" Anti-Magnetic Plaster for AFVs, by Major J.W. Thompson and Mr. C.E. Hollis.

The purpose and initial application of Zimmerit are best described in an interview with Herr Robert Pertuss, chief engineer at the Henschel tank manufacturing company in Kassel, Germany:

"One day Herr Kniepkamp (of Heereswaffenamt) showed up at Kassel and reported that the Russians had used magnetic mines, which tank hunting teams attached to the sides of our tanks and could be made ineffective by a thick grooved layer of some form of cement applied over the surface of our vehicles. With this method the magnets would not get a strong enough grip to keep the mines in place. Our Purchasing department was able in an afternoon to telephone I.G Farben chemical company to find out what materials would be suitable, available and quickly obtainable. It had to be fast drying and stone hard when dry. Two days Later the first drums of "Nitro-Spachtel" arrived. Using improvised tools made out of sheet metal we made a test application. In only 3 hours the material was dry and could be painted. The drying time shortened considerably when we used a blow torch to dry the material. Tigers ready for delivery the day after the "Nitro-Spachtel" arrived were coated and painted and we delivered Tigers with the Material until the end of production."

We found that most of the publications on the ingredients of  Zimmerit repeat the content of one leading publication in the JAN-APR 1983 issue of Armoured Fighting Vehicle News Magazine.

Information from a secret British Intelligence Objectives Sub- Committee report:

The information is now unclassified and entitled, "Zimmerit" Anti-Magnetic Plaster for AFVs, which was reported by Major J.W. Thompson and Mr. C.E. Hollis. The report is dated July 1945, and is not complete due to insufficient information, or the failure to locate persons with detailed knowledge of the subject. The investigation was started with the hope that a way might be found to defeat magnetic mines used against British armor in the war with Japan. In 1943 the Germans adopted a thick coating for the vertical armored surfaces of their tanks. This coating was designed to defeat the affects of mines placed on armored vehicles, mainly tanks, by determined Russian infantry assault teams. The mines were attached to the tanks and held in place by magnets built into the bottom of the mines. The function of the "Zimmerit" was simply to provide a non-ferrous magnetic gap between the steel armor and the magnets, in other words a non-magnetic stand-off. Early in 1944 samples of Zimmerit were taken from captured vehicles and instructions for its use obtained from prisoners of war. The composition of Zimmerit was analyzed by C.S.A.R. and found to be the following:

Polyvinyl Acetate-25%, as binder or glue;
Wood Fiber-10%, as filler;
Barium Sulphate-40%;
Zinc Sulphide-10%;
Ochre Pigment-15%, for the dark yellow color.

On August 14, 1945 the investigating team visited the Henschel Werke at Kassel, Germany and interviewed the Director of Production and Production Engineer. The following information was obtained. The Zimmerit was received in drums from Chemische Werke Zimmer in Berlin, but they thought production had taken place in various centers because of the large scale demands, and because of factory dispersal. The material arrived in a consistency of soft putty (others have compared it to paste, plaster or plastic). It contained a volatile solvent smelling like acetone. No thinners were added before use as it worked very easily even when handled by inexperienced personnel. The surface of the tank did not need to be prepared before applying Zimmerit, but it was normal to coat the vehicle with anti-corrosive primer. The Zimmerit was applied to the surface in two coats, using a sheet metal trowel. The first coat was 5mm thick and was marked out in squares using the edge of the trowel. This coat was allowed to dry at ordinary  temperatures for 24 hours. The second coat was applied thinner and marked in wavy lines with a metal comb. The crisscross squares increased the adhesion of the second coat, while the comb markings gave a camouflage finish, plus poor contact for mines. After the application of both coats, the surface was treated by a gas blow-lamp to harden it. This took about an hour per tank and no difficulty was experienced in getting satisfactory hardness without the Zimmerit becoming brittle. (I have seen samples of aged Zimmerit and it reminded me of compressed sawdust.) During the hardening process the solvent was removed by the heat of the blow-lamp on the surface. The chief thing to watch was not to leave any soft spots which could be brushed off the vehicle if not hardened properly. If the Zimmerit was not heated with a blow-lamp it took eight days to harden. This was impractical considering the urgent need of tank delivery to the front. The Production Engineer of Henschel Werke said that the company did not help in the development of Zimmerit, but simply applied it to vehicles. He thought that Zimmerit was dropped late in the war due to the development of better anti-tank weapons. No mention was made of how successful Zimmerit was, however, when the British Army captured the Henschel Werke they removed about 100 tons of Zimmerit. The investigating team next visited the Karl Freudenburg A.G. in Weinheim, Germany and talked with the company’s Polyvinyl Acetate experts. Again, this company had not helped in the development of Zimmerit, but did work on the P.I.B. mineral oil adhesives for sticky bombs. The Polyvinyl Acetate was used as an emulsion in camouflage paints and as a solvent such as Ethyl Acetate and Toluene during the war. It was mentioned that C.W. Zimmer of Berlin was well known for paint manufacture during that time, and probably used Polyvinyl Acetate.

On visiting I.G. Farbenindustrie A.G. Hochst, Germany, the Plastics Development Manager and  Production Manager were interviewed. They said that they had heard of the C.W. Zimmer Co., but also knew nothing of the development of Zimmerit. It was also mentioned that such things were kept secret. After referring to the company’s records it was learned that Mowilith 20 (a Polyvinyl Acetate) was sold to the C.W. Zimmer Co. In July 1943, but they had no idea if the company or its personnel still existed. The general properties of Polyvinyl Acetate were discussed. Mowilith 20 was 50% benzene solution (this is what smelled and was burned off with blow-lamps). It had an average MW of 3500 (Staudinger viscosity method, 1 - 2% solution) and a melting range of 40 to 50 degrees C. It was also confirmed that the blow-lamp would remove the solvent and adhere the Zimmerit to the armor, thus increasing its resistance to shock. In regard to adhesion, it was suggested that a clean or just painted surface would be better than a greasy or rusty one. Also, that Polyvinyl Acetate with a pigment mixture (Zimmerit had 15% ochre) were somewhat water-resistant, but due to thermal behavior of Polyvinyl Acetate its use was limited in plastics as it became brittle when cold. In conclusion, the team decided that the C.W. Zimmer Co. was responsible for Zimmerit and every effort should be made to contact them. They also were wondering if Zimmerit, thinned down, could have been sprayed on vehicles to speed up application time. However, no follow-up research was done due to the end of WW2.

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Personal demonstration of the Nazi Hafthohlladung antii-tank mine.

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Right hand side mudguard, second segment from the front.
Usually not treated with Zimmerit, although video evidence proves an exception.
Click here for footage of a captured German Königstiger II tank featuring mudguards treated with Zimmerit.

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