Re: Cullet

Russ Strodtz <railfreightcars@...>

My vote is with Mr Thompson. That is why the cullet was sent back to
the plant that the bottles were made at. One would think that they would
almost always have batches of brown glass stewing since beer bottles
were one of their biggest products.

Another thing comes to mind. I'm sure most of us are familiar with the
heavy, sort of waxy, cardboard cartons that refillable beer was/is sold in.
That was what the new bottles were shipped in. I'm sure their thinking was
that even though they had to be taken out to be filled those cartons had
to be bought at some time in the process and their use would cut down on

The purchasing and delivery of packaging materials may have been the
reason that there were so many CP and CN cars to be found around the
glass plants.


----- Original Message -----
From: Anthony Thompson
To: STMFC@...
Sent: Tuesday, 30 October, 2007 01:07
Subject: Re: [STMFC] Cullet

John C. La Rue, Jr. wrote:
> I suspect that any coloring agents would have been removed when the
> cullet was melted in the furnaces, much as carbon and trace additives
> are removed when scrap iron and steel are melted...the additives unite
> with the limestone to form slag, which is removed, thus leaving pure
> iron.

Different process, John. In fact, colored glass is QUITE hard
to re-clarify. You can mix brown and green glass, but not put either
one into clear glass. And blue glass is a serious contaminant for any
other glass color.
There are several reasons, but an important one is that glass
melting is a very slow process, mostly due to the viscosity and
resulting slow circulation and mixing of the glass--24-hour melts are
common, whereas steelmaking can be accomplished in 90 minutes or less.
(That's the reason that glass recycling really saves little energy; the
process takes about as long, and about as much energy, whether you use
raw materials or cullet. But you DO take all those bottle-size voids
out of landfills.) Another difference from iron refining is that there
is no slag equivalent in glassmaking.

Anthony Thompson
Dept. of Materials Science & Engineering
University of California, Berkeley

Join to automatically receive all group messages.