#### JohnJones

##### Member

Harrit et al. report finding red/gray chips with a thickness of 10-100 microns in WTC debris. They conjecture that these are some form of thermite. Jim Hoffman (http://911research.wtc7.net/essays/thermite/explosive_residues.html) supposes that this material was painted onto the steel supports of the WTC towers and contributed to their collapse.

The same publication by Hoffman quotes a figure of about 4 MJ/kg for the energy density of thermite, and assumes a density of 4,400 kg/m^3.

The thickness of the steel in the core columns of the WTC buildings tapers as they go up (http://911research.wtc7.net/wtc/arch/core.html). At the mid-section of the building it is thought to have been about two inches thick (about 5 cm).

From these data, it is straightforward to calculate the maximum increase in temperature of the columns that could result from ignition of the thermite layer. What follows is a best-case analysis: it is assumed that the thermite remains in good thermal contact with the steel throughout its reaction; all the heat from the thermite is deposited in the steel, and that there is no cooling of the steel by convection, radiation, or conduction along the column. We assume that the thickness of the nanothermite layer is the maximum thickness of the chips reported by Harrit.

Consider one square meter of column surface. The thermite layer is assumed to be 100 microns thick, so its total volume is 0.0001 m^3 and its mass is 0.44 kg. It will therefore release 1.76 MJ of energy. The same area of column corresponds to 0.05 m^3 of steel, with a mass of 400 kg. The specific heat of steel is about 500 J/kg.K. So the expected temperature increase is

Delta T = 1,760,000/(400*500) = 8.8 C

This shows that Hoffman's paint theory cannot be true.

The same publication by Hoffman quotes a figure of about 4 MJ/kg for the energy density of thermite, and assumes a density of 4,400 kg/m^3.

The thickness of the steel in the core columns of the WTC buildings tapers as they go up (http://911research.wtc7.net/wtc/arch/core.html). At the mid-section of the building it is thought to have been about two inches thick (about 5 cm).

From these data, it is straightforward to calculate the maximum increase in temperature of the columns that could result from ignition of the thermite layer. What follows is a best-case analysis: it is assumed that the thermite remains in good thermal contact with the steel throughout its reaction; all the heat from the thermite is deposited in the steel, and that there is no cooling of the steel by convection, radiation, or conduction along the column. We assume that the thickness of the nanothermite layer is the maximum thickness of the chips reported by Harrit.

Consider one square meter of column surface. The thermite layer is assumed to be 100 microns thick, so its total volume is 0.0001 m^3 and its mass is 0.44 kg. It will therefore release 1.76 MJ of energy. The same area of column corresponds to 0.05 m^3 of steel, with a mass of 400 kg. The specific heat of steel is about 500 J/kg.K. So the expected temperature increase is

Delta T = 1,760,000/(400*500) = 8.8 C

This shows that Hoffman's paint theory cannot be true.

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