Please note that nothing at all in what follows proves, or even hints at, either the presence, or the absence of explosives, or ammunition in the church.
The purpose of this investigation is to show two things, firstly that there was enough potential fuel already present at ground level within the church to melt the bells and secondly, that this fuel could easily have reached a high enough temperature to melt the bronze from which the bells were cast without having to invoke the presence of any additional substances, such as hidden explosives. This is a very cold-blooded examination of the known facts of a horrible event.
I spent a day in the reference section of my local library and with the assistance of one of the librarians dug out various books and British Standards (BS) on fires, fire fighting and compositions of various materials. I say now that much of what follows is a bit on the approximate side, due to the difficulty in estimating the exact mass of combustible materials involved. However, I do not think that there can be much doubt as to the main conclusion, even if the total quantity of fuel was much less than my estimate.
1) That there were at least 400 persons in the church, made up of 200 adult women, the remainder being children of both sexes under the age of 15 (the exact numbers have proven difficult to establish exactly due to the state of the remains and the fact that some women and children were killed in the barns with the menfolk).
2) Adults had a mass of 50 Kg (Kilograms) each, children, 25 Kg each.
3) Body fat has been taken as 15% of total mass of all bodies, this is probably a low a figure (especially for children) and comes from biological textbooks and previous knowledge.
4) The church was built to seat 350 persons (this is a fact, not an assumption) and had wooden seats for this number.
5) The seating was in the form of conventional wooden pews or chairs, probably made of oak.
6) There was very little other combustible material in the construction of the church at ground level. The roof joists and steeple framework were of wood. All exterior roof surface areas were of non-combustible tiles, as was that of the steeple.
7) The soldiers piled brushwood, straw and other combustible materials on the bodies near to the entrance door after their being shot (this from the eyewitness of Mme Rouffanche and surviving soldiers at the Bordeaux trial in 1953).
8) The fire was started by the use of phosphorous according to Mme Rouffanche.
It has been pointed out by some people that the soldiers of the Der Führer (DF) regiment would not normally have access to phosphorous, being a Panzer Grenadier unit and not a pioneer group. The Das Reich Division, of which DF was a part, did have a pioneer unit, although I do not know their geographical location during the 9th and 10th of June.
Mme Rouffanche was in no position to make calm rational observations on the day and it must be admitted that she could have been wrong. It is even possible that she was reacting to suggestions made to her after the event as to what was used to start the fire.
In Bordeaux, during the trial in 1953 of the 21 men from Das Reich, the presiding judge suggested that they had used flame-thrower fuel to ignite the church and feed the flames. Perhaps they did, but none of the men confirmed it.
In any event, by whatever means, the fire started near to the entrance and under the steeple.
1) Total fuel available at ground level was made up of: 200 x 50 x 15% to give total fat content of adult women present, plus 200 x 25 x 15% to give total fat content of children present. This gives a total of 1500 Kg for the women and 750 Kg for the children, making a sum total of 2250 Kg of combustible fat (i.e. 2¼ tonnes, a significant quantity).
2) Seating of (probably oak) for 350 persons gives a total of 2450 Kg for the wood, based on an average figure of 7 Kg per seating position. This estimate is based on existing church pews that I have examined.
3) No allowance has been made for other items such as, clothing, kneelers, hymnbooks, or the additional material the soldiers are known to have piled on top of the bodies near the main entrance door.
4) An ignition source is assumed.
5) Total fuel available for combustion was thus 4700 Kg. Note this is a minimum figure for fuel at ground level.
6) It is well known that not all the bodies were entirely consumed and that a total of about 30 were identifiable as human remains, even if their actual identity could not be determined due to the state of burning (a few people, mostly children were positively identified by their relatives), so a correction of 30 x 50 x 15% gives a deduction of 225 Kg for unburned fat (assuming all unburned bodies were adult).
7) Total fuel consumed at ground level is thus 4475 Kg.
8) An average figure of 16,000 kJ / kg (kilojoules per kilogram) is assumed for heat output (data from BS 4422 and 'Underdowns Practical Fire Precautions' 3rd edition). Total thermal energy available from combustion was thus, 4475 x 16,000 = 71,600,000 kJ.
Note 1) 'Underdowns' mentioned above does quote specific figures of thermal output for all common materials, but also states that an average value of 16,000 kJ / kg can be used for most purposes without introducing serious error and so this figure has been used for all combustible material in the church.
Note 2) I have examined the partially melted bells which are on display in the church and from these remains have estimated that the total mass prior to the fire would have been about 100 Kg. In order to allow for the possibility of the church being equipped with more bells than are on show (ones which were more thoroughly melted) I am going to assume that the total mass of bells on the 10th of June was 300 Kg.
Note 3) It is taken, a) that the Specific Heat Capacity of Bronze is 360 joules per kilogram per degree Kelvin, b) that the total mass of the bells in the church was 300 kilograms and c) that the temperature increase needed to melt the bells was 1400 degrees Kelvin (same intervals between degrees Kelvin as between degrees centigrade). Thus the total energy in Joules needed to melt the bells was: 360 x 300 x 1400 = 151,200 kJ. From the above it can be seen that there was about 470 times more thermal energy available to melt the bells than was required. Even if the mass of the bells was much greater than the 300 Kg assumed, there was vastly more potential energy available than needed.
Note 4) Irrespective of the quantity of energy available, if the flames could not reach the necessary temperature and for the necessary time, the bells would not melt.
9) It is assumed that the fire was in progress for about 1 hour before the roof fell in ('Underdowns Practical Fire Precautions' 3rd edition). Over this time period there was sufficient fuel available at a rate of delivery high enough to cause the partial melting of the bells. Most fires of this type go through the phases of a slow start, a rapid build-up to a peak and then a slow decay. My guess is that the bells melted before the roof fell in and at around the peak of the fire's intensity.
10) The main fabric of the church was of non-combustible stone (Granite) and a good thermal insulator.
11)) As has been claimed in, Tulle and Oradour, the German point of view, "The bronze bell of the church melted. Fire is not sufficient for this. Wood burns at 200-400 degrees centigrade, while bronze will not melt at less than 1250 degrees."
However this statement is only partly true, in that wood on its own in the open air can burn at about 350 degrees centigrade. However in Roman times (and even before then) the dead were normally cremated on an outdoor wood fuelled open framework, which normally had oil added and this certainly reached temperatures sufficiently high enough to consume bone (between 800 to 1000+ degrees centigrade).
Bronze is a generic name for an alloy, which has a wide range of constituents in addition to the main one of copper. For example the addition of about 10% tin lowers the melting point and increases hardness. Nevertheless, taking a figure of 1250 degrees C as the melting point of the bells it can be demonstrated that this temperature can easily be achieved with just a wax candle flame. 'Underdowns' quotes that a simple candle burning in open air has a temperature 'envelope' within the flame ranging from 800 to 1400 degrees centigrade when measured with a thermocouple.
12) The weather was fine and sunny. There had been overnight rain, but the day itself was dry.
Running the model:
1) The fire started and the wood of the pews / chairs / brushwood began to burn.
2) The bodies began to char / burn and fat began to burn using the clothing as a wick, at this point the temperature of combustion would have risen from that of the wood only at about 350 degrees centigrade to that of wood + fat at about 800-850 degrees centigrade. It is worth realising that in the normal process of cremation of human remains following a funeral, that a large part of the energy required to burn the body comes from the body's own fat.
Note that an absolute minimum temperature at ground level must have been in the region of 800 degrees centigrade; as this is the minimum temperature required to consume bone (Underdowns). It is known that very few bones were found after the fire in the main body of the church, the majority of the remains being in the form of ash and fragments.
3) A wax / tallow candle flame burns between 800 and 1400 degrees centigrade when measured with a thermocouple and the actual peak temperature is about 200 degrees centigrade higher than the measured value ('Manual of Firemanship' and 'Underdowns Practical Fire Precautions' 3rd edition).
4) The fire would have continued for some time, fed by air through the broken windows, with the heat rising into the roof and steeple areas. The granite construction of the church would have prevented any major loss of heat, or combustion products to the outside environment.
5) Eventually a, 'flashover' would have occurred, when flame would have been present in the smoke within the body of the church. At this point the inside of the church would have been an inferno, contained by the roof. The roof timbers would have started to burn, but it would have taken another half to three-quarters of an hour for it to collapse.
Note that at this time the temperature at roof level would have been considerably higher than at ground level.
6) The main conduit for the rising smoke, flames and products of combustion would have been up through the well-ventilated steeple. Looking up from within the church beneath the steeple, the view today is through a hole about 1 metre in diameter in the stonework and this is the route through which the bell ropes reached the bells.
7) After the flashover the flames from the fire would have been funnelled up through the hole like the flame of a blowtorch or Bunsen burner. Remember that at this time the flames were fed by a combined wood / fat fire and would easily have reached or exceeded that of a candle flame in temperature i.e. over 1400 degrees centigrade. This high temperature, backed up by over 71,600,000 kJ of heat supply, could have melted the bells (which were directly above the hole) several times over.
Note that a force fed flame can reach even higher temperatures than a simple diffusion flame. This is the principle of the blast furnace, blow in lots of additional air (oxygen) and the potential temperature increases, given a sufficient supply of fuel, so the above temperature estimate is somewhat conservative.
8) When rescuers reached the church on the 11th June they remarked on the layer of ash that covered the floor to a depth of several feet in places. They also noted that the wooden confessional box was unburned. The confessional box was to one side of the main body of the church and would have been protected by the draft from the windows flowing past it.
1) The phenomenon known as, 'spontaneous human combustion', is simply that of a human body burning slowly, but with great localised heat due to the 'wick effect' of fat soaked clothing. Bones in the affected area are reduced to ash, which implies a local temperature of over 800 degrees centigrade. It is a characteristic of this process that the surrounding material in a room may be unburned.
2) Large volumes of air were available to feed the fire through broken windows (Mme Rouffanche broke one in order to escape); the only exit at high level was through the steeple (until the roof collapsed).
3) My efforts above are those of a non-fire expert. Any attempts at refining them will be welcomed.
4) I have not used any figures in the above for either the floor area or internal volume of the church as in my opinion they were not limiting factors.
5) Nothing in the above proves that explosives were not present in the church, it only shows that the bells could have melted without any other materials being present other than the stated fuel in the church at the time (the fat of the bodies and the wood from the seating).
© Michael Williams: revised January 2006