From: Louis Boyd <boyd@apt2.sao.arizona.edu>
Subject: Re: firebrick
Date: 27 Dec 1997
Newsgroups: rec.crafts.metalworking

mlightner wrote:

>I live next to a place that makes and refurbishes drill bits for drilling
>wells. They've been where they're at for quite a while, judging by the
>size of the refuse-heap that is spilling down the hill in back of the
>place. Amongst the debris is a bunch of primitive looking rusted out
>ovens and there are two different kinds of bricks, that were lining them.
>The bricks vary in color from yellowish-tan to a light beige color. Some
>are real light, weightwise, and seem rather fragile, but the majority of
>them are heavy with the name EMPIRE impressed on one side. Can anyone
>tell me how to determine if these are indeed firebrick? Would sitting out
>side for years do them any harm, if that's what they are?

They are undoubtedly refractory "firebricks".  The lighweight delicate
ones have excellent insulating characteristics.  They are made by mixing
sawdust with the clay. When the bricks are fired the sawdust burns away
totally and leaves the spongelike material.  The insulating property
comes mainly from the trapped air. The heavy ones are much more rugged
and will probably take slightly higher temperatures but don't insulate
nearly as well.  Commonly furnaces have the heavy bricks inside the
insulating bricks for mechanical strength.

If they are still mechanically sound they should be fine to reuse.  If
they are wet, dry them slowly in an oven before trying to use them in
a furnace.  They don't "wear out", but the surface can be damaged from
wear or spalling, or the bricks could be contaminated.  From you're
description the steel furnace jackets are what was bad and they junked
the whole thing.  I worked a couple of summers during my college years
doing QC work in the lab of a company which made similar bricks.

Lou Boyd