Remembering a Veteran: Wing Commander Frank Brock, OBE, RNAS, RAF

By James Patton

Wing Cmdr. F.A. Brock

Frank A. Brock OBE (1884–1918) was the son and heir to the manufacturing firm headed by Arthur Brock, known as "the Fireworks King." Employing at its peak over 2,000 people, the C.T. Brock & Co. fireworks factory at Cheam, (then in) Surrey, was Britain’s largest of its kind and also produced a variety of devices for the military during the war, including over 30 million Mills bomb fuses.

Being experienced with explosives, in October 1914 Frank Brock volunteered for the artillery. A month later he was transferred to the navy, then became a flight lieutenant in the Royal Naval Air Service (RNAS) in January 1915. Although he was a civilian pilot, he never flew for the RNAS; instead he founded and headed up the Royal Navy Experimental Station at Stratford, located in London’s East End. On 1 April 1918, the RNAS and the Royal Flying Corps (RFC) were combined to form the Royal Air Force, and Brock was appointed to the newly created rank of wing commander. 

During the First World War he is known for the invention of several devices and processes. Among these are:

The Dover or Deck flare, which was a one-million-candle-power incendiary device. These were used to protect cross-Channel steamers from U-boat attack by washing out a periscope’s field of vision. 

Colored glass filters, which improved clarity in cameras, binoculars, periscopes, and optical signaling devices by removing less useful colors. These were a sort of simple precursor to modern infrared devices. 

The Brock bullet, a standard SMLE .303 round-tipped with the contact explosive potassium chlorate, was developed by Brock at his family’s factory and at his own expense. In September 1916, the zeppelin SL11 was destroyed by RFC Lt. William Robinson (1895–1918), flying in a BE2c with Brock bullets in his Lewis gun, for which feat he was awarded the Victoria Cross. Later there were developed two alternative designs of anti-zeppelin ammunition, which were called the Buckingham bullet and the Pomeroy bullet, and the machine gun feeds thereafter contained a sequence of all three types.  

Brock is probably best known for his work in developing artificial smoke and fog. This research resulted in two different products. On the small scale he developed chlorosulfonic acid bombs, a substance which when discharged into the air, fuses with atmospheric water to form a dense, opaque, and highly acidic fog. Brock used this technology in the E-float device which could help a merchant ship screen itself from a following U-boat. Modern smoke grenades have also used Brock’s technology. 

Brock also developed a process for large-scale production of artificial fog for use by ships. A generator tube was attached to the exhaust of the ship’s engines or boilers. This device was partly filled with water, which was heated by surface contact with the exhaust pipe or stack. Into this water was discharged a steady flow of calcium phosphate, which the heat converted to phosphoric acid. This was injected into the exhaust plume where it combined with atmospheric water to produce a dense and highly corrosive fog. Like all forms of gas release, the atmospheric conditions had to be right to prevent the fog from enveloping the ship itself. 

Marines & Sailors Storm the Zeebrugge Mole from HMS Vindictive

This system was employed by the Navy at the raid on Zeebrugge, Belgium on 22–23 April 1918. Brock was present on the cruiser HMS Vindictive to supervise the fog production. Likely bored, he decided to go and find a German fire direction station so he could study their technology. Like one of Henry Morgan’s pirates, Brock went ashore armed with a Webley revolver (some say two) and a cutlass. He was never seen again.