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I'm reading the airship pilot manual for the Goodyear K-Type blimps and in the table of "Empty Weight", at page 18 under the heading "Pyrotechnics", there are listed "24 Bronze Powder Markers" for a total weight of 48 lb.

Googlin' I just found references to makeup stuff and artists' colors, but those applications don't fit under the heading "Pyrotechnics"...

Can anyone shed light?

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  • $\begingroup$ Curiously - both bronze/brass and aluminium were scarce resources in WW2, but more-so for the central powers and Japanese. $\endgroup$
    – Criggie
    Commented Apr 29 at 22:29
  • $\begingroup$ Although the Japanese captured the major supplier of tin at the time (Malaysia), they did not have a domestic copper supply. However, the US and allies had to deal with (re)finding tin supplies. My grandfather, a mining engineer, spent WW2 in the Andes evaluating all the old mines for reopening to supply tin (and copper). $\endgroup$
    – Jon Custer
    Commented Apr 30 at 16:16

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Bronze powder drift signals could be dropped on the ocean surface as a marker.

It seems most likely that there was not any pyrotechnic element to the powder - that is, it didn't burn on the surface in any way. The patent for the Surface Marking Signal (1944) - basically a bomb-shaped object to be dropped from an aircraft - provides the best description of how bronze powder was used as a marker. The powder

provides for the marking of a continuous, homogeneous, and visible spot on the surface below... to provide a marking on the surface such as open water... to mark the location of a previous seen object.

The invention consists of a a powder contained in a streamlined shell. The shell is such that on striking water... it will break and release the powder... The powder is of a composition which will spread into a single homogeneous visible spot when it is released on the surface... suitable materials are pale gold bronze powder and sodium fluorescein salt.

Surface Marking Signal source

In the United States Official History of the Sea Search Attack Group (1942 - 1944) there is a description the crew of a Douglas B-18 Bolo carrying out an anti-submarine attack:

As there were oil slicks astern of the submarine to approximately mark its position, no bronze powder signal smoke or smoke flare was dropped.

It's a bit ambiguous: I imagine it would work quite well sitting on the surface of the water and glittering if the conditions were right. However, if we take "bronze powder signal smoke" to be a single phrase, then it indicates that there was some airborne element to the bronze powder, rather than just being a passive marker.

Another WW2 document entitled INSTRUCTIONS FOR COORDINATED EFFORT OF DESTROYERS AND PLANES AGAINST ENEMY SUBMARINES says:

Planes of the Inner Air Patrol may drop aluminum or bronze powder bombs to mark suspected contacts, for their own benefit in making further investigation.

while Naval Aviation News of October 1943 warns:

bronze powder spilled from a drift signal container caused serious corrosion to the bottom of a seaplane due to galvanic action with aluminum and salt water... extreme care should be exercised in handling bronze powder drift signals.

Aluminium Bronze Powder was also used as to add to the coating of aircraft, but this is not what it was for in your manual.

Aircraft quality Aluminium Bronze Powder source

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  • $\begingroup$ "I imagine it would work quite well sitting on the surface of the water and glittering if the conditions were right. " I imagined the same before posting my question, I figured a sort of rocket that blasts the bronze powder on the sea surface, but mine it's just imagination… $\endgroup$
    – gboffi
    Commented Apr 29 at 13:17
  • $\begingroup$ "Aluminum Bronze Powder". Make up my mind, is it aluminum or bronze??? $\endgroup$
    – FreeMan
    Commented Apr 29 at 17:55
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    $\begingroup$ @FreeMan Aluminum Bronze - it's a bronze (copper alloy) made with aluminum instead of tin. $\endgroup$
    – R.M.
    Commented Apr 29 at 19:51
  • $\begingroup$ thanks, @R.M. Confusing just on the face of it... $\endgroup$
    – FreeMan
    Commented Apr 30 at 12:35
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    $\begingroup$ @gboffi I don't see an issue with those dates - the patent is for something that uses "Bronze Powder" so we should expect the powder to have been invented some time earlier. $\endgroup$
    – MikeB
    Commented Apr 30 at 16:02
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In addition, WWII practice bombs were filled with metal powder to produce an easily-visible splash mark when they struck the ground, so the bombardier could see how close he got to the intended target.

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