On Tue, 6 Apr 2004 12:06:19 -0700, Eleanor Breen <[log in to unmask]> wrote:

>Hello Histarchers: I have a question about
>heat-altered or fire-reddening of subsoil.  At a site
>where the floor level is know, in your experience,
>what is the distance between heat source (hearth,
>etc.) and the discolored soil?  In other words, how
>far above grade can the heat source/floor level be and
>still have fire reddening of the soil?  Does the
>presence of brick lining the heat source transmit heat
>better, thereby causing more extensive soil reddening?
> We are interested in both the depth and horizontal
>extent of the heat alteration.  We are trying to
>figure out if distance between floor surface and
>heat-altered subsoil can be inferred by the extent of
>soil reddening.
>
>Thanks, Eleanor Breen
>
>Assistant Archaeologist
>Historic Mount Vernon

Dear Eleanor,

At the SAA meeting in Montreal this past weekend, I heard a paper preented
by researchers who may have fairly detailed ethnoarchaeology data they can
give you about color changes due to thermal exposure. They applied their
experiment to sandstone samples, but did so by covering the samples with
different layers of matrix, over which hot coals were place, so they may
have analogous data that would interest you. You can probably find the
authors' addresses through the SAA member directory:

Daniel Winkler and Dustin Blodgett: The Thermal Alteration of Silicified
Sandstones from Western Wisconsin.

Best wishes,
Chris