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Showing posts from August 5, 2012

Brick Shelves

Part of the infrastructure required for brick-making is a place to dry the formed bricks before they are fired. Since this brick-making operation is being built from the ground up (literally) I had to design and construct a shelving system. It is composed of simple wooden frames with slats for shelves, to allow for the maximum flow of air.

At first I was worried that the slats were making lines on the bricks. I was thinking that I would have to let them dry longer on the sand rows, or touch up each brick, or make different shelves, but then I found a very simple solution: a shim to angle the slats to almost the same slope as the brick.

Working with Second Mold

There's something about the friction between the clay and the mold that seems to require an impact to loosen it. The pieces of Second Mold do not come off the brick as easily as I had hoped. I also have a hard time getting very clean edges, as the clay sticks to the lip of the mold. I thought that my mixture was too wet, but even with a drier one the problem remained.

Second Mold

I wanted to make a mold in parts, with the thought that I could minimize the distortion of the brick by setting it down on the sand instead of having to drop it. I like the corners on this mold better- the CNC machined corners on First Mold have a radius due to the drill bit. This one is more tedious to work with, however, because of the separate pieces.

Kiln Stacking

Oval kiln with rectangular bricks, Castel Viscardo, Italy

Hoffman kiln, near Radzymin, Poland

Stacking a kiln with bricks to allow for ventilation and even firing is quite an art. As well, the places where they are touching during firing often get 'kiss marks', lighter patches of colour, so the stacking influences the final appearance of the brick.

One thing about having a non-rectangular brick, though, is that it is very easy to stack them in a way that allows the passage of air.

I ended up just laying them directly on top of each other, in two layers of three courses. This allows me to fire 105 bricks per kiln
Now, I just have to hope for the best...

Creases and other Clues

The woman who gave us a tour of the H.G. Matthews factory pointed to a sample wall. "This is our handmade line", she explained. "You can tell, of course, by the beautiful creases in the bricks". 

In fact, creases are one of multiple clues that indicate the molding process of a brick. If you ever get a chance to see all sides of a brick, it's quite easy to tell. 

Creases show that the original mixture was stiff, not liquid; their direction indicates the force applied, and their unevenness reflects the imprecision of hand-thrown clay.

Check the location and nature of the stamp, if there is one, for further clues. Any brick with a 'frog' and a stamp on its largest face (see here for an example) probably means that a five-sided mold was used.

Bricks made by extrusion are obvious; their extruded sides are smooth and uniform, and most of the time you can see subtle lines from the die. The other faces are rougher, having been cut off. The ones in the photo below a…