[PW] Re: Esoteric Name

[Kay Lancaster]

On Mon, 18 Dec 2006, david meadows wrote:

> There's no formal name; a guy named fiorelli did the first ones a century
> ago (using plaster) and in the 1980s they tried doing it with epoxy resin.
> The cast itself is usually referred to as a 'cast'
> 
> dm

Mumble years ago, one of my physical anthropology profs always 
termed these "positive casts" -- but he was a man given to very 
precise speech.  The ash was the "mold".

If these were considered classical fossils, like fossil fish in 
limestone, the shapes in the ash bed would be called "impression 
fossils" or molds.  If you fill an impression with material like 
plaster, the resulting plaster is a "positive cast" (it looks 
like the thing that made the impression).  If you think of biting 
into a piece of wax, you'll get a mold or impression of your 
teeth.  Fill the holes in the wax with plaster, and the plaster 
forms a positive cast of your teeth. Take those plaster teeth and 
press them into clay, and you'll have a negative cast of your 
teeth, just like the initial wax mold you made.

Kay, who's a whole lot more familiar with plant fossils.