Stephani Stephenson on thu 21 sep 06
The architectural ceramics workshop is underway here at the studio
and a fine, motivated, fabulous group of folks here.
Sharon from Iowa raised a question today about making brick..
We talked about differences and similarities in claybodies suitable
for architectural ceramics and tile
(typically used as a cladding or hollow built forms) and fired brick,
Her interest is in solid brick suitable for exterior use in northern
climates.
Traditionally common brickmaking occurred at the site of a clay deposit
The most desireable and economical practical clays were those
suitable for use , as is , without need for additives,
Unless a specialty facing, paving , or engineering brick was made, it
was not economical to
add grog or sand, etc. to the clay..
Smaller operations would be able to sometimes mix clays. etc to produce
a higher quality brick, etc.
but typically the operation would simply relocate when a clay seam
was exhausted
So brickmaking clays varied,from location to location.
.Prior to the industrial revolution, in the European tradition, I know
that handmade bricks were formed quite wet, and allowed for 15%
shrinkage. They were knocked into a clot them slammed into a wooden
mold, the preferred wood being Beech, and the clay coated with sand to
assist in release. With handmade brick, the clay was often dug in the
fall, stones removed and clay possibly pugged, then left to lean over
winter. In spring it might be worked in with additives such as sand,
but also could be mixed with coal dust or ash.
one of my sources, David Hamilton's "Architectural Ceramics" notes the
following
"All bricks which are to be fired must be made of a clay which
includes some fluxing material and the most common of these is calcium.
Many alluvial clays include calcium of a very fine particle size...the
calcium acts upon the alumina and silica in the clay to produce a
strong and dense brick at an economic temperatiure of about 1830
F(1000C).........
Common bricks are not vitrified and normally not fired above 1000
degrees C..............
Bricks which are to be used as facing bricks are more carefully made
and quality of clay is more rigorously controlled, sometimes fired
beyond 1000 C for greater strength and improved
color....................
Engineering and paving bricks are fired to point of vitrification or
to a temp approaching vitrification in a reducing atmosphere, achieving
maximum strength without deformation ............(my note: iron acting
as flux in reduction) .. also discusses long soak during firing to
improve strength and allow for outgassing
,etc. Hamilton also notes that engineering brick has porosity of less
than 2%, and used in Europe to pave roads...often half the thickness of
common brick...doesn't mention porosity of common or other brick....
my question: does anyone have a good claybody suitable for making solid
brick?
I'd say any temp up to cone 5.( much of the architectural terra cotta
is fired at cone 3, though some much higher. )
If I were making one my first instinct would be to make an
architectural or sculpture body with at least 35 % grog. The only
commercial body I know which could handle the thickness is
Aardvarks' Dixon Red or for a white, their Fullerton White... and some
of the architectural bodies could handle the thickness as well
BUT I am not sure these are quite in the same 'family' as the old
brick clays ! I don't want to presume anything about them, such as
quantity and size of grog
I know I have seen some bricks which appear to be rather smooth
bodied...
so how can those thick as a brick bodies be smooth without cracking,
etc?
so anyone out there have some tantalizing info on how to make a brick
clay which they would like to share?
Stephani Stephenson
steph@revivaltileworks.com
http://www.revivaltileworks.com
Elizabeth Priddy on fri 22 sep 06
If you break a few bricks and look at the surfaces
compared to the inner tooth, they are frequently
different.
So one thing I would say is that the process of making
the brick makes the surface information different from
the compositional information.
OR:
The surface may be "glazed" or burnished, so don't go
by that to glean information.
Not much help, but very interested,
E
Elizabeth Priddy
Beaufort, NC - USA
http://www.elizabethpriddy.com
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Stephani Stephenson on fri 22 sep 06
Yes , some differ from inside to out, some don't.that's the wonderful
thing about brick as well as pots and tile, a record of the gorgeous
array of clays from the earth and the methods of forming and firing as
well.
different firing methods, different bricks for different purposes...
some are smoother inside to out, some with a variety and size of
'inclusions' for lack of a better description
Firing method, fuel used , as well as the composition determines the
surface, the core, the color,the strength etc. how consistent in
appearance it is, on the surface and throughout
clay composition and processing , additives, what fuel was locally
available, firing cycle and the heat work in the cycle, whether brick
fired in a clamp or a kiln, and the 'work' the brick eventually
needed to do and the conditions it would be subject to ....
since common brick didn't increase the value of clay very much,as
little time and effort as possible was put into the brickmaking
process. hauling the clay any distance would be enough to increase the
price beyond what brick could bring. less $ per weight of almost any
'burned' clay product.
surface shine on them was not burnished so much as interaction of clay
surface to heatwork/atmosphere, ie. fluxing iron, ash,calcium and
other body fluxes, some soluble and carried to surface perhaps in
drying. perhaps surface temp showing shine as clay reached
vitrification...
I've lately done some things with a thixotropic red clay with so
many soluble salts it produces
a chocolate 'glaze' on every outer surface, any surface exposed to air
on drying
looks very much like a salt glazed surface, other surfaces a dry
'brick' red
you see this type of surface on many bricks
also a family of glazed brick, which would have been much more
expensive and which blur the 'line' between brick and tile! ....
still hoping to find out more
Stephani
ELizabeth wrote
If you break a few bricks and look at the surfaces
compared to the inner tooth, they are frequently
different.
So one thing I would say is that the process of making
the brick makes the surface information different from
the compositional information.
OR:
The surface may be "glazed" or burnished, so don't go
by that to glean information.
Not much help, but very interested,
E
Stephani Stephenson
steph@revivaltileworks.com
http://www.revivaltileworks.com
Vince Pitelka on fri 22 sep 06
Okay darling Clayarters, gather around and I'll tell you a story about
bricks. This really is fascinating. Back in the days of the Industrial
Revolution, bricks were fired in large kilns called "clamps." The bricks
were stacked almost solid inside the kiln, with channels through the stack
to conduct the heat from the fireboxes to the flue. The bricks closest to
the channels and especially closest to the firebox would be overfired and
often melted. Those a little farther away would be fired a dark brown. As
the bricks were farther from the heat source the color would lighten through
shades of red-brown and brick-red, to a soft orange-red, until finally there
would be a measure of bricks that weren't fired at all and would be reserved
for the next firing when the clamp was unstacked.
At that time, for common use like factory and utilty buildings, bricks would
be sold as "mill-run" without any sorting, and the common appearance would
be a brick wall with a variety of colors in the brick, depending on how hot
they were fired. For fancy construction - stores, public buildings, and
private homes, the bricks would be graded as they left the factory, so the
customer could purchase bricks of uniform color - that was the "status" look
at the time.
Now, most building bricks (not fire bricks) are extruded from giant
pugmills, and special equipment is available to skim a varying coat of
slurry on the surface of the brick, so that the color changes from
brick-to-brick through the run. These bricks are more expensive - you pay
extra for a load of bricks that has variegated color through the batch - for
what was once "mill-run" - the cheapest available. That's great marketing on
someone's part.
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
Jim Kasper on sat 23 sep 06
Hi Stephani,
My last trip to Crete, Il. I dug up about 1000 pounds of clay
from my folks back yard. "Chicago brick clay" The entire area has great
clay about 6 inches down.
It was my last visit to my childhood home before new owners took
possesion. I did not have much time, but i conditioned a few pounds of clay,
made a few pinch pots, and animal figurines and pit fired them. I now have a
little piece from that home that, "I can't go back to" staring at me from
next to my computer.
I am starting to realize that with proper conditioning this clay
could have quite different properties. I am guessing that i could increase
the maturation temp by doing several washes to remove solubles.
Depending on what kind of project, i would think that a field
trip to a brick making region would be an ideal place to get "brick clay".
Here is a fascinating site about bricks:
http://www.ricks-bricks.com/
Looking forward to hearing more about your brick quest.
Regards,
Jim
Zafka Studios
Jensen Beach, FL
http://zafka.com
772-334-3070
Snail Scott on sat 23 sep 06
On Sep 21, 2006, at 11:15 PM, Stephani Stephenson wrote:
> ...so anyone out there have some tantalizing info on how to make a
> brick
> clay which they would like to share?
>
The town where I live now has an old brick factory
still in operation - the last in this region which used
to have many. I begged a tour from them last year.
They have great huge piles of material behind the
factory building - one of a local clay, and one of shale,
all sitting out and overgrown with weeds. They dump
the stuff into the mixer in equal parts (it seemed),
where it got pulverized, mixed with water, and pugged
out directly as extruded bricks, all in a continuous
process. As the brick pugs came out of the pugmill,
they ran between rollers (selected from among several)
for various 'rustic' textures, then were sprinkled with
sawdust and what looked like white clay dust (again
for rustic effect). A multi-wire harp then sliced each
pug into a dozen bricks. Very stiff dense clay with no
evident temper; almost no moisture content. Helluva
pugmill!
The bricks then moved down a conveyor belt and
were loaded by hand onto the kiln cars. These then
rolled directly into the drying kiln and straight on
into the firing kiln and out the other end, in a VERY
short firing cycle. I don't want to mis-state the exact
number of hours, as I may have forgotten, but it
was less than a day from mixing the clay through
to the finished fired brick.
The finished brick was palletized by six guys who
each loaded just one row of a stack, working at a
sort of merry-go-round that moved each stack past
their station and on to the next stacker. After each
stack was complete, a mechanical arm shoved the
stack onto a pallet, then the next stack on beside it,
until the pallet was full. Each guy worked a 1000
brick shift, then went home, however long it took.
They were really cranking, though, and usually
figured on an early quitting time.
I was surprised at the amount of manual labor
being used, but the foreman told me that adding
new mechanized equipment was difficult, since it
had to be synched up with the existing older
machinery. It was nearly impossible to make it
match up, so it was more efficient to keep hiring
hand labor.
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