Hi all-
Very quickly, since Chris and Larry have pretty much answered this
question, but Julie might consider checking with her local/regional
Fire Investigators or Police Forensic unit. If the brick is from a
structure, rather than a refractory or manufactory context, these
people have fairly elaborate data that will help to determine the
temperature of building fires. I am sure they could help you with
this particular question, and you may even consider bringing along
some other types of artifacts, including melted glass and other
non-corroded metals.
Remember as well that a burning building is full of microenvironments
where heat and smoke flow unevenly through the structure based upon
air flow patterns and the surrounding fuel. One burned brick will not
tell you the overall temperature of the entire building fire, it may
mislead you.
I genuinely recommend talking to these people. My older sister is a
fire fighter (as are several readers of this list) and I have found
that firefolk:
1. love nothing more than to sit around with other people and talk
about fires, fighting fires, the heat of burning buildings, and
fighting fires in hot burning buildings. They will likely help you
for free and even become interested in your research.
2. know a great deal more chemistry, physics, and archaeology than
either you or they think they do.
Let us know what you find out!
Cheers,
Tim
----------------------------------
Timothy Scarlett
University of Nevada, Reno
Dissertation Fellow
Archaeometry Division
Missouri Universities Research Reactor
601 South Providence Road #601F
Columbia, Mo 65201
[log in to unmask], [log in to unmask]
----------------------------------
These views are my own and do not represent the views of my employer.
Hold on a moment.
I don't have an employer.
Never mind.
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>From: Chris Salter <[log in to unmask]>
>To: [log in to unmask]
>Subject: Re: - Brick Vitrification
>Date: Thu, Feb 8, 2001, 12:35 PM
>
>Julie,
>
> Yes bricks will vitrify given high enough temperature. The
>temperature
>at which this occurs depends entirely on their composition. Bricks made of
>fireclay will withstand very high temperature, in excess of 1500 C, whereas
>bricks made of clays with high alkali and iron content vitrify relatively
>easily perhaps as low as 800 C.
>
> Another factor that controls the vitrification temperature, is the
>type of heat involved. If bricks were in contact with the fuel then the
>vitrification temperature can be reduced by the fluxing action of the
>chemical
>components of the fuel, particularly the alkali elements.
>
> Mortars are another problem, a pure lime mortar would not vitrify but
>revert to quick lime. However, the lime would have been mixed with some
>form of
>filler so that again the composition will be the controling factor.
>
> Knowing the composition, one can look at the equilibrium phase
>diagram
>that nearest approximates to the composition to get an idea of whether the
>material is likely to be highly refractory or not. There are also various
>formulae which give estimates of the initial melting points of material of
>these sorts of compositions, unfortunately I do not have any of the
>references
>to hand.
>
>Chris Salter
>---------------------------------------------
>Materials Science-Based Archaeology Group,
>Department of Materials,
>Begbroke Business and Science Park,
>Sandy Lane,
>Yarnton,
>Oxford OX5 1PF,
>
>Tel. Office 01865 283722
> Probe 01865 283741
>Fax. 01865 848790
>Mobile. 0777 6031608
>E-mail [log in to unmask]
>
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