History: Physics Laboratory during the occupation period 1940 – 1945

Physics Laboratory during the Second World War [translated]

From 1941 until the liberation of the Netherlands in 1945, Mr Zuurmond worked at the Physics Laboratory that was part of the Dutch PTT during the occupation period. On 1 December 2000, he visited the museum “Waalsdorp”. He was asked to put his memories about the Second World War period in writing. His story follows below.

Report by Albert (Ab) Zuurmond, born October 27, 1925. employed by the PTT, Central Workshop (CWP), Binckhorstlaan The Hague, April 15, 1941, as pupil instrument maker. In the summer of 1941, seconded to the Physics Laboratory, together with Jan Oldenhof, presumably shortly after the laboratory was incorporated into the PTT.

Physics Laboratory during the occupation period 1940 – 1945

The [Measurement Building, after the capitulation incorporated in the PTT organisation as] Physics Laboratory was located along the edge of the – at that time still completely bare – Waalsdorpervlakte halfway to the left of the sand plain seen from the railway to Scheveningen that is now the route of the Landscheidingsweg. Of three separate buildings in a row, indicated with A-B-C, the actual laboratory was housed in the elongated B-building. The two smaller ones, A and C, were at a short distance from them and had an additional function. Immediately after the occupation of the Netherlands, the specific task of the laboratory was stopped, namely research at the service of military resilience. The German occupiers now decided on the work. A ‘führer’ headed the laboratory in the capacity of a so-called Einsatzleiter. The future became dicey.

The staff of the laboratory (I mention the first name or initials as far as I remember) during the occupation years consisted of:

  • Head of the laboratory: ir. J.L. van Soest, a friendly gentleman, who took his hat off for the staff. He did not get much to the fore. My impression was that he led a somewhat withdrawn life in his room. He actually got in the way of the German occupiers and was later made redundant. He found shelter elsewhere in the PTT. Ir. Gratama was then designated as the head.
  • Staff: ir. Gratama (electrotechnical), Piket (physicist) and Mulders (presumably a chemist).
  • Electronical engineers: Hendriksen, Insje, Koebrugge, Ten Pas and Piet Steunebrink (amplifier specialist).
  • Administration: Willem de Visser (head) and Bart Koppenberg.
  • Drawing office: Berkelaar.
  • Instrumentmaker: master instrument maker Nico de Vries (head), master or journeyman Van den Berg, Elkerbout, Van Gijn, Groot, Saeijs, Tabbernee and the youngsters Wim Cramer, Theo Keizer, Jan Oldenhof, Dirk Osseman, Henk Stap, Bertus Vlaardingerbroek and Ab Zuurmond.
  • Maintenance: carpenter J.C. Riem.

In addition, there were the occupants of the laboratory:

  • Einsatzleiter Sarfer, an SD-officer from Dresden,
  • Workmaster Suster from Linz in Austria,
  • a ‘bread’-NSB member who was “obliged” in service, and
  • a younger colleague of his, a Dutch son of a German father (left later).
Map of the Measurement Building in 1941
Map of the Measurement Building in 1941

Ir. Van Soest had a room to the right hand of the main entrance (left front), Sarfer’s room was left. The administration room lay behind it as well as the drawing office. Subsequently, right-hand access to a fairly spacious corridor with left and right rooms and workspaces of the engineers, the electronic engineers and Suster, with at the back a storage room for parts and the entrance to the central heating cellar. The corridor ended with sliding doors that gave access to the instrument-makers.

Ir. J.L. van Soest
Ir. J.L. van Soest

In addition to the sliding doors to the corridor, the instrument-makers had their own entrance at the rear (dune side) of the building. In fact, it was the new part of the laboratory that had roll-down shutters. The old part had shutters with pens. De Vries and Tabbernee each had a key of the back entrance. Who arrived first in the morning opened the door. Nobody was yet present in the building when the ‘craftsmen’ had to start at 8 o’clock. Sometimes we were waiting in the rain or freezing cold for the key and that sometimes gave rise to harsh words!

Upon entering, there was a rectangular hall, with the sliding doors to the left to the material storage area and to the right the access to the instrument makers. Opposite the outer door was the entrance to the canteen at the front of the building behind the material storage area. In the hall, there were two toilets and washbasins on the right and the door to the room of De Vries. The cloakroom was on the left. The first task of the young people was sweeping the workshop floor every morning (a cleaning service was not available). The working time was 8 hours a day and on Saturday till 13.00.

In my memory, the following machines were installed for used by the instrument-makers:

  • two drills
  • a large lathe and two or three smaller ones
  • a milling machine
  • a carpenters bench
  • a saw bench
  • a hand form bench
  • a large hand cutting scissors with waste bin (good for your own work).

Along the window edges, there were long fixed work tables of, I believe, eight places each. Cabinets with small materials stood against the cross walls. Behind the workplace of Tabbernee – right back from the hallway – was the door to a small smithy. It contained, among other things, a blacksmith fire with an anvil, a device for brazing and a polishing machine. In the canteen, there was also a small nickel bath.

Construction and sabotaging of jammers. After I had worked for Gratama for some time, I had to assist with the construction of jammers intended to make listening to the news of the so-called English channel almost impossible by means of a fluctuating and more or less rasping waving tone, a very unpleasant noise. It was the young people who had to do that work. A jammer consisted of an elongated base made of sheet metal with edges of plus-minus 15 centimetres high folded down at the bottom and provided with two handles on the short sides. The base was estimated to be 2 metres long and ¾ metres wide. There were four large (transmitter) lamps of plus-minus 40 centimetres height, a few large coils, two or four large vertically arranged plate capacitors, a heavy power transformer, and a number of smaller parts. An electric motor with a toothed aluminium disc on the shaft completed the whole.
The disk rotated past two capacitors and thus caused the frequency modulation. The large capacitors were made of sheets of aluminium with a thickness of three millimetres. They each consisted of two plates of plus-minus 20 x 30 centimetres with rounded corners. Between the plates, there was a small space that could be changed with adjusting screws. After the pieces of aluminium were sawn to size, the sides were smoothed with a metal woodcutter (the foot greased). Beautiful shiny curls came from. A coaster made of that material is still used at my home, hence the exactness of the indicated thickness. The jamming station was standing with short sides on workbenches or boxes, so sitting on the ground one could work underneath (good for sabotage). ‘Werkmeister’ Suster supervised the work (De Vries did not interfere) and therefore regularly sized up the situation.

From left to right the Austrian Hr. Suster, Ab Zuurmond, Willem Cramer, Theo Keijser, Henk Stap and Jan Olcdenhof around one of the German jammers.
From left to right the Austrian Hr. Suster, Ab Zuurmond, Willem Cramer, Theo Keijser, Henk Stap and Jan Olcdenhof around one of the German jammers.

‘Werkmeister’ Suster came from the German service station and, as far as we could tell, he was not a Nazi. We had a lot to do with him. He was a pretty cheerful man with humour, you could laugh with and around him. If he had explained something, he would say: ‘Siehste, siehste, so scheisst man in that Wieste‘. When one of the elderly came in after a holiday with a beard, he cheerfully greeted him with: ‘Guten Morgen Herr Petrus‘ (great laughter). He often sat in shorts in the open door of his storage room and was delighted when you said he was ‘already nicely coloured.’ You sometimes got a slice of bread or a piece of sausage from him (and that’s what we actually wanted to do). All in all, it could have been worse. “Freilich,” he would have said. Sarfer, on the other hand, was a real proud Prussian, usually walking uniformly and straight through the building, hands on the back and a glance here and there. Before and after a telephone conversation he said loudly: ‘Heil Hitler‘. He could not be sneered at! As far as I remember I have never seen him laugh.

Nevertheless, a lot of sabotage was made: for example by pulling a pencil line on the (black) winding of a coil so that the wiring burned down during the test run; a lamp that fell or was weakened by first putting it under a considerable tension (Steunebrink); connections were soldered incorrectly; parts could not be found or were lost; allegedly being busy but doing nothing, and so on, and so on, delayed delays. A final check for transport was the exact opposite of what it should have been: nuts were not tightened, screwed connections as loose as possible, soldered points ‘stuck’ and the like. On one occasion a completely dismembered shipment was returned. You had to be inventive and always come up with something else in order not to fall under suspicion. It was done tacitly, but afterwards, we rubbed our hands. However, it remained a dangerous ‘game’.

The test run consisted of connecting the device to the mains voltage (plug in the socket) and converting the main switch. Suster was of course always present and told us to put the left hand in the pocket to prevent accidents due to high voltage (current through the heart region). It was always a thrilling affair: we were there as innocent boys and had inner fun when something again was pounding, sometimes the sparks splashing. Especially the flashing of a large transmitter lamp was nice to see, but also the crackling burning of a coil gave satisfaction. We then struggled to keep our face in the fold and were very surprised by ‘how is that possible?’ Meanwhile, Suster was excited and irritated by our ‘ignorance’, called desperately: ‘Verdammt nochmal‘ or ‘Scheisse‘ and walked away. He probably could not ‘lose’ such a setback to Sharfer (the relationship between the two seemed cool to me).

In building A – the former station of the military weather service – contained, according to me, a huge truck. Suster occasionally warmed up the engine to keep it ready. I had to go with him to building A once to pick up something. He opened the big doors, climbed skilfully into the cab and started the engine. He signalled to wait and walked away. Meanwhile, the speed of the engine began to rise to a huge roar. Alarmed by the noise, he rushed back and set the engine on stationary gas. ‘Macht nichts‘ [does not matter], he said laughing, ‘Der Engel lauft wie ein Teufel‘. I did not know the function of the Colossus. It was possibly a vehicle to escape.

Lantern made of 'waste' (1941)
Lantern made of ‘waste’ (1941)

Odd jobs. A lot of repair work was done: everything that went out of order at home was repaired at the laboratory. In addition, we made anything and everything (a hanging lantern with no less than 116 copper rivets, for example, I still have at home). As much as possible was tried to produce as little work as possible and still be supposedly at work. It was the art of camouflaging that everyone did. In addition to individual odd job work, we also worked on a series of electric clocks for personal use. In order not to arouse suspicion, the work split up into parts and divided between the workforce. Such a beautiful, all-metal table clock has still been used at our home. He ran on (the then) 127 Volts mains.
I also remember that in one way or another a batch of rapeseed was bought by one of the elderly men. In order to get the oil out, a press was made consisting of a kind of worm gear rotating in a cylinder. The whole was fixed on the milling machine and switched on. The rapeseed ended up in the worm wheel via a funnel, which crushed and compressed it. The oil dripped into a container and the pulp came out of the cylinder like a solid sausage mass. It did not work really well.

Bart Koppenberg got his hands on street brine from the municipal warehouse. We dissolved the brine in water and purified it with filter paper. The solution was then brought to a boil on a hot plate so that the water evaporated. The salt remained intended for personal use and extra income. Applied physics! And [a lot] later we made so-called Majo-stoves (also called soviet-stoves) meant to be able to cook (and heat) with very little fuel. A Majo consisted of two iron pipe sections in each other: an open outer surface of approx. 20 centimetres high and 15 centimetres in diameter, and an inner pot with fire grate (of large nails), less high and wide. The device was placed on top of the coal stove after the lid had been lifted. Then there was fired with everything that was flammable. Sometimes there was leftover anthracite. The combustion gases passed the pan with the scarce food on top of it and were transported through the chimney via the outer casing – which was nicely warm. The stove was a miracle of ingenuity and a rescue in the hunger winter. [The Majokachel was invented in 1944 by Johan Bubberman from Rotterdam]

News from overseas. In the instrument-makers part of the building, at Tabbernee’s work table – in the farthest corner from the corridor – was a concealed radio on a cupboard behind several boxes. The radio was tuned to the jammed channel ‘Radio Oranje’ from England. If it was safe, the radio was quickly turned on and the sliding doors to the hallway closed with a ‘guard post’ that looked through a crack. When Sarfer or Suster was approaching the situation was brought back to ‘normal’ in no time and everyone was working ‘well’ again. The Germans sometimes found it strange to see the sliding doors closed because they were usually open. This is why there were thoughts about an electric alarm from an ‘outpost’, but I can not remember if one was realised. We also had to look out for the NSB member, a somewhat colourless person. I remember that once there was a questioning by Sarfer because of something of out of control. He threatened with extradition to the Sicherheitsdienst (SD) or Schutzstaffel (SS). Fortunately, it was over with a sizzler. De Vries once again insisted on us being careful.

Lunch. The young people were appointed to get a hot meal every day at one of the soup kitchens in the city. Presumably, the food came from the Obrechtstraat. A hefty transport bike was available for this, with a square steel carrier on top of the front wheel, on which the messtin could stand. With the empty messtin of the previous working day the trip to the soup kitchen where sweaty men with bare torso were stirring in large steaming kettles with a kind of oars. The fact that there was some perspiration in the food, did not bother anyone. From such a kettle ‘our’ messtin was filled for three-quarters full, after which the lid was clicked onto the rim, the heavy case was put on the transport bike and lashed with some belts. The driving and manoeuvring with the loaded transport bike was no fun, especially not in bad weather. Once ‘the man with the bike’ had been spotted along the windows – you looked forward to it – everyone rushed to the lunchroom for an (enamelled) tray that was scooped on the spot. Wim Cramer was the one who usually took care of the bragging rights and that was done with a half litre shape on a long handle. The food consisted mostly of a kind of thin stew of cabbage, carrots, beets, beans and the like. The soil remains were distributed among the youngsters. Riem did the dishes.

Railway station Waalsdorp
Railway station Waalsdorp

The Atlantikwall. Coming from the railway station on the Oude Waalsdorperweg a wall came in sight, which had been erected as part of the ‘Atlantikwall’. The thick concrete wall had a kind of trapezoidal shape and was about three metres high. In order to reach the laboratory, you had to pass through an opening in the wall that was ‘guarded’ by sentinels. By presenting an ‘Ausweis’, you could continue past the camp of the Grüne Polizei (former camp Waalsdorp of the Grenadiers and Hunters), which was located between the wall and the laboratory area. It was ‘Sperrgebiet’. Hence the Ausweis that all “lab technicians” had in their pocket.

A wall belonging to the Atlantikwall
A wall belonging to the Atlantikwall

I still remember that when we arrived there in the morning, a caterpillar vehicle from the camp (by way of exercise?) was driving upward on planking that had been built against the wall on the campsite. On the outside, there was not (yet) an exit. That caused the vehicle to plunge over the top into the sand and the crew tumbled out. Do not laugh was the motto!
That reminds me of a rather – less pleasant – incident: I walked with a colleague from the railway station towards the wall when a few German officers caught up and pushed us aside. ‘Danke‘ I said when one of them came back and snapped: ‘Wàs danke‘ and then beat me flat with my flat hand. Watch out!

Searching about. We went as young people, at noon and in good weather, to the plain or the dunes in order to ‘browse’. At a distance of 50 metres of the laboratory towards the dunes, there were two transmitter masts 65 metres high. We sometimes climbed up to watch the area or to release homemade aeroplanes made from balsa wood. The masts had a plateau of about 2 x 2 metres at the top, so you could easily stand with a few men. If you held the parapet and rhythmically ‘imparted’ (like with a swing) with two or three men, you saw the mast moving with respect to the foundation. Incidentally, you could, of course, see all sorts of things in the German camp.
Wim Cramer once brought out a real cannon, a front loader of about 20 centimetres long, complete with bullets and powder, all made by himself. We have fired this ‘muzzle’ in the dunes: it worked perfectly! For example, a metal plate was pierced; so it was really a deadly weapon. We also made little bombs from pieces of iron pipe. One side was squeezed in the vise, then homemade powder (Wim Cramer) was shaken and the other side was squeezed. Subsequently, these ‘explosives’ were detonated in the dunes by mixing black powder with something inflammable which was lighted.
You had to stay covered because those were dangerous ‘toys’ (but after all we were working in a laboratory). We did not have to be afraid to be discovered, because the Germans regularly held shooting exercises in the dunes. Therefore, there was no suspicion in the camp or in the laboratory. The ‘elderly’ probably never knew what we were doing.

The Waalsdorp execution site. The Physics Laboratory was on the deserted bare plain, so there was a good view of everything that happened there. Reich commissioner Seyss-Inquart, for example, came along on horseback with a few officers or alone with his daughter for a ride through the dunes. There were also German (punishment) exercises: with the tiger creep through the puddles or in the summer heat a round of the plain, and so on. The most drastic event that regularly occurred: an execution. Then a blinded prison car drove by on the road to the execution site at the end of the plain. Then a firing squad marched past, rifle over the shoulder and carrying a few buckets of lime. Then gunfire was heard after which the car drove back across the plain. A little later the firing squad (sometimes singing) passed again, towards the camp.
Once in a while, we went to the pool at the execution site, a dune behind the first bushes: a frightening place. According to my memory, there was a wooden stake. There were flattened bullets and there was turned sand on which blood traces were visible. All in all a very moving experience which we underwent in silence. We walked around in the sand and quietly returned to the laboratory. It is a mystery to us that it took a long time after the war for this execution site to become (nationally) known.

Memorial place Waalsdorp
Memorial place Waalsdorp
Memorial place Waalsdorp
Memorial place Waalsdorp

Physics Lab housed at the PTT on the Binckhorst. When the Atlantic Wall was completed – probably in late 1943, early 1944 – the laboratory was moved to the PTT complex at the Binckhorstlaan in The Hague. The Central Workshop (CWP) and the Central Warehouse (CM) of the PTT were located there. The lab was housed on the highest floor of the CM. From there we could perfectly see the V2’s taking off (with a lot of noise). Sarfer once stood with us when it happened and gleamed with pride. The reason for the forced move was that all of Scheveningen and the western part of The Hague had to be evacuated and became ‘Sperrgebiet’. The Germans wanted to have a large field of fire in case of an invasion on our coast. The Dutch piers in the dunes also had to go ‘heraus‘.

Under the disguise of a ‘high-frequency heater’ project, work was being done in secret on a radio transmitter ‘Herrijzend Nederland’. This was assembled in a loft on the ground floor of the CWP building. I think that only Insje had the key to that loft. Almost everyone worked on the transmitter, although no one knew exactly what he manufactured and what its purpose was. This was, of course, a safety precaution.
The transmitter was intended to be used after the expected liberation of the Netherlands starting at the beaches of The Netherlands. Because the invasion started in France, the station was only in the air a lot later, built up and operated by Piet Steunebrink and Ten Pas. Hendrikse and Gratama acted as announcers (they were radio amateurs). The studio was housed at the front in the top of the CWP building. An antenna was stretched to one of the two gas tanks on the other side of the Binckhorstlaan, presumably from the CM building.

Transmitter Herrijzend Nederland III which broadcasted from May 1945 to 1946 (gramophone music + news). It was operated by the staff of the laboratory. The transmitter was later used as a retransmitter at Beek airport.
Transmitter Herrijzend Nederland III which broadcasted from May 1945 to 1946 (gramophone music and news). It was operated by the staff of the laboratory. The transmitter was later used as a retransmitter at Beek airport.

Storage of surrendered amateur transmitters. In the course of the German occupation, all amateur amateurs had to hand in their radio equipment. These transmitters were stored in the basement of the CM building. We sometimes dived into the cellar to ‘sniff’. The channels, large and small, were piled up to the ceiling, a huge number. There were very professional-looking specimens in beautifully finished cabinets, but also primitive-looking pieces of equipment. In that basement, there were also some steel cupboards in which materials were stored and what had to be kept out of German hands.

This radio set was secretly made for the Dutch resistance
This radio set was secretly made for the Dutch resistance


Accompanying tapping-key
Accompanying tapping-key

The hunger winter. As far as the soup kitchen is concerned: we now belonged to the PTT CWP / CM staff, so we ate in the basement (due to air alarm) anything that turned up as the meal at around 11 o’clock. It consisted of thin stew as we were used to at Waalsdorp, but much more one-sided and less of ‘quality’, too often beets, if I remember correctly. But you were always hungry. Sometimes food stemming from the PTT was distributed among the staff: some potatoes, some winter carrots, a few sugar beet, a bag of flower bulbs, and the like. At Christmas 1944, there was some butter and cheese. On one occasion I broiled some bulb rings on a hot plate during the break when Sarfer came by and asked what it was: ‘Blumenzwiebel?’. He wanted to taste it, so he took something, drew a bad face and walked quickly.
In the course of the hunger winter, probably in the beginning of 1945, Swedish bread was once distributed among the staff, probably also stemming from the PTT. In my memory that was half a loaf per person, a treat from the top shelf. I started to feast on it, and almost all of them did.

Air alarms. Air alarms were common, sometimes more times a day, especially towards the end of the war. Then there was also a siren in the building via the public address system. Everyone then had to go to the shelter under the building as quickly as possible, where you sat side by side on long benches. People were reading, puzzling, rumoured, and so on. I had a – then-popular – pocket chess game in book form, which was very useful to continue the game at the next air alarm. If the ground was booming, there was an anxious silence. I vaguely remember a test with gas masks in that cellar (in Waalsdorp gas masks were practised in a hut across the plain with a man or ten at the same time and tear gas as test gas).

End of employment and return to the Waalsdorpervlakte. I do not remember much about conditions and work directly after the liberation. On 3 December 1945, I returned to Waalsdorp, but now as a soldier. I had registered as an OVW member of the Communication section located in the Alexanderkazerne in Waalsdorp, an environment that I knew. It was also the end of my laboratory time, an instructive period of friendship and solidarity, which always stayed with me. Recently I learned that the lab returned to Waalsdorp at the end of 1947.


I have put these memories on paper to the best of my knowledge. However, they do not claim any completeness. Because of the time span of more than half a century, many things cannot be ‘retrieved’, especially the work that was done outside of our group of young people. That was not talked about. I believe that, in addition to civil-scientific assignments, I was obliged to work on Lorenz transmitters, of which a single copy seems to have been realised. The delay must have been enormous too for that project. Mainly my own experiences and observations are shown here. It is surprising that so many, in fact, less important, but in my opinion, nice and enlightening details could be noted. Some of those minor occurrences indicate that the period was not always stressful.

I liked to fulfil the request of ir. A.W.M. van der Voort, curator of Museum Waalsdorp, to record my memories about the ups and downs of the laboratory and its employees during the German occupation of the Netherlands. During my visit to the museum, he was able to show me some interesting details by means of documentation and photographs. In consultation with him, I decided to donate the lantern mentioned under ‘own work’ to the museum provided it is included in the displayed collection. The museum agreed with these conditions. I would like to thank Wim Cramer and Piet Steunebrink for some valuable additional information and tips, which they passed on to me after reading the draft text.

Ab Zuurmond (2002)