[Steppes] Roman Standards

[uilliacc]

a concrete mixed with pumice, or fired bricks made with pumice would 
form a type of refractory.  in either case or with stone the mold would 
have to start out warm-- stone would require hot to prevent rapid heat 
transfer in the initial contact.  Pumice and refractory actually prevent 
heat transfer in that while their surface heats up, the conduction 
through the material is very limited... pumice or concrete/refractory 
would be very superior to concrete or sandstone in this regard...the 
surface of the mold wouldn't have to be real smooth to produce glass 
that was-- the glass isn't that fluid


AlKudsi at aol.com wrote:
> I believe that the molds were actually carved sandstone, although very 
> logically, they could have been carved pumice (although you wouldn't 
> get as smooth a finish with pumice). They very well might have been 
> concrete, though...it has been years. I do remember our guide telling 
> us that quite a bit of the aqueduct system was made of concrete, so, 
> yes, concrete or a concrete aggregate would be a strong possibility 
> for a mold as well. Either would have a slower rate of heat exchange 
> which would naturally anneal glass.
>  
> Glass buried for a long length of time tends to go cloudy, I would 
> presume due to long-term interactions with minerals in the ground, and 
> moisture. Changes due to acidity or the alkaline nature can do that. 
> We saw an archeological dig in Pompeii that was bringing up quite a 
> bit of what probably should have been clear glass but that was foggy 
> in places.
>  
> Wow, this is an exciting discussion on a topic we don't often see in 
> the SCA!
>  
> Saqra