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another firebrick question

updated fri 28 feb 97

 

Toni Martens on fri 7 feb 97

I have found a source of FREE firebrick.
A crematorium here in Durban burnt down.
Any reason apart from the grizzly aspect of brick from a crematorium
why they should not be used in a kiln?I have had a look at them and
they appear to be in fair condition, nice sharp edges etc.
Toni M in Durban where the humidity is enough to drown in!

sam wainford on sun 9 feb 97

Toni Martens wrote:
>
> ----------------------------Original message----------------------------
> I have found a source of FREE firebrick.
> A crematorium here in Durban burnt down.
> Any reason apart from the grizzly aspect of brick from a crematorium
> why they should not be used in a kiln?I have had a look at them and
> they appear to be in fair condition, nice sharp edges etc.
> Toni M in Durban where the humidity is enough to drown in!
Hi Toni, Sounds like you have a lot of work ahead of you if you intend
to salvage these brick. My 50 cubic foot salt kiln is built entirely of
salvaged hardbrick except for the arch. There are a few major problems
which need to be considered before you undertake such a huge project.
Are the bricks mortored together? If so, a cement mortor instead of a
fireclay mortor has probably been used, which is very difficult and
time consuming to remove. If a fireclay mortor has been used, it will
be somewhat easier to chip off with a brick hammer, but cement in the
morter makes it bond to the brick. If the brick has already had a lot
of the "good" burnt out of it, it's likely to crumble as you try to chip
off the cement. You can see the evidence of heat on the bricks by
looking at the rings of color change moving out from the hot face of the
brick. Should you manage to reclaim these brick, turn the brick around
for your kiln, putting the side exposed to the least amount of heat
facing the inside of your kiln. Don't be tempted to leave any of the
old mortor on the brick unless you know for sure it will withstand the
heat of stoneware temperatures. I don't know how hot a crematory burns,
and what the service temperature of the old mortor is, but I wouldn't
take the chance on letting that old mortor melt, bloat or explode or
compromise the structure of your kiln. Plus, your brick will need to be
level, and this would be easier if you start as close to clean as you
can get. This really is a huge job. If you salvage 1000 brick (about
what you need for a 50 cubic foot kiln) you will be cleaning all 6
sides! Very labor intensive, but like you say, they are FREE. One
other thing about used brick is that they tend to warp and shrink at
different rates depending on their placement in the old structure. I
found almost a quarter inch difference in some of my salvaged brick. So
be sure to that each course is level as you build, and that your corners
are plumb.
I used new brick for my arch. The quality of used brick is
questionable--especially brick salvaged from industrial applications. I
would think twice before using it in an arch. Good luck! Sam