Valetta Aircraft Spraying the BW Simulant - Zinc Cadmium Sulphide

This declassified Porton Down film, which is Crown Copyright, shows a Valetta aircraft making a number of passes in front of the camera - all the time spraying the Biological Warfare simulant - Zinc Cadmium sulphide. These experiments shown in this film were conducted during March 1958, and were conducted to determine the characteristics of an aircraft mounted Zinc Cadmium sulphide dispenser. The resulting information was then used in Porton Down's later public area BW experiments, some of which (the Large Area Coverage or LAC) contaminated vast swathes of the UK. A BW simulant is a supposedly harmless substance which mimics the physical properties of a real BW agent, in this case, size (between 1-5 microns). BW simulants are used in BW experiments in which, for safety reasons, a real BW agent could not be used.

A similar procedure was adopted for the 1963/64 Norwich Trials. An aircraft, this time a Devon, sprayed the BW simulant Zinc Cadmium sulphide, at a rate of 2-3 lbs per mile, as it flew along a 62 nm track across Norfolk - at a distance of 24 miles upwind of the city of Norwich. When the massive aerosol cloud reached its target area, Porton Down scientists conducted clandestine sampling of the air at a large number of locations, across the city and surrounding countryside.

MoD test of aerial spraying over Norwich

The Penetration of built-up areas by Aerosols at night - Porton Down Public Area Biological Warfare Experiments on Norwich

MoD test of germ warfare aerial spraying over Norwich

This was a Ministry of defence test carried out on the city of Norwich on January 13th, February 10th, March 16th and April 14th 1964.

These are PDF documents which claim to have been declassified in 2000 and describe an experiment by the ministry of defence where the city of Norwich was sprayed by aircraft with a substance known as "Silicon treated FP", which is claimed to be "innocuous in the concentration which were expected to occur on the ground".

These documents outline the nature of the experiment and the involvement of the local police in it.

Background to Porton Down experiments

During May 1963, the War Office Chief Scientist sent a memo to the Secretary of State explaining the type of public area experiments that were being conducted in the UK by Porton Down. As can be seen in the covering letter, the experiments were conducted in a high level of secrecy because "knowledge of them by unauthorised persons could be politically embarrassing."

PDF Download:

Porton Note No 188 18 August 1959 - here

Porton Field Report No 515 13 Nov 1957 - here

Porton Note No 74 Extract 13 November 1957 - here

DOC Porton Field Trial Report No 610 The Penetration Of Built Up areas at night - 1963 experiment - here

CDEE Porton Programme Report 2 64 The Penetration of Built Up Areas By Aerosols At Night PDF file - here

MOD Internal Review re Zinc Cadmium Sulphide FP public area experiments - here

DOC Porton Note No 188 The Long Distance Travel of Particulate C - here

DOC Secretary of State Briefing Memo Public Area CW BW Experiments May 1963 - here

See also Biological Warfare Experiments in Dorset 1963-75