I just came across this unanswered question while researching the thread archives.
In his book, THE LONGEST NIGHT, 10 - 11 May 1942 Voices from the London Blitz, Gavin Mortimer wrote about the use of thermite in incendiaries.
“A solitary incendiary bomb was a straightforward piece of ordnance. In size and shape it resembled the truncheon of a London policeman, and its 1 kg weight was also similar. A British Government handbook at the start of the Blitz described an incendiary bomb as ‘designed to give an intensive combustion at a high temperature by burning the body of an electron which is ignited by the ‘thermite’. To the average slum dweller in Stepney or Southwark, it was all gobbledgook. All they knew was that for a few moments an incendiary bomb burned very brightly and with a strange ‘psss-psss-psss’ sound.” pg.110
“And as the [German] crews of KGr100 prepared for take off shortly after 10 p.m. most of their aircraft carried in each of their eight bomb chutes four ‘breadbaskets’. Four breadbaskets in one chute equalled 144 single incendiary bombs. Multiplied by eight, each Heinkel that taxied down the grassy L-shaped runway at Vannes was carrying 1,152 incendiary bombs.” pg.111
“But what the handbook hadn’t described in any great depth was the incinerating qualities of just one incendiary bomb. For approximately fifty seconds it burned at 2,500C as the thermite priming produced its own oxygen. When this fantastic heat had melted and ignited the main magnesium component of the bomb it continued to burn for twenty minutes at temperatures of 1,300C.”
pg.146-147
Consider your question answered Dave!