Adobe is an ancient building technique dating back to 8300 BC. The bricks are fireproof, durable, biodegradable, and provide excellent thermal mass to a building. In the fall of 2012, I gained experience building with bricks, including making the mortar and constructing walls; however, the adobe bricks were already made at the time. Luckily, I was able to participate in making the adobe bricks during an afternoon in preparation for an earthen oven. Our mix ratio was 2.5 parts sand to 1 part clay with a few handfuls of straw as the fiber. We mixed using tarps and good ol’ man power. Water is added to taste, although we found out that a wetter mix made for nicer, more uniform bricks. You want it to be firm, able to hold its shape, and not too watery. Definitely wetter than cob. A clean, dry place is necessary for proper drying. The drying time depends on your weather conditions. In Oregon, it can take three weeks or more during the spring months. It is best to rotate the bricks every week for even drying.
The brick form can be made using a range of materials. including wood, metal, or plastic. Ours was made using wood for the base and branches for handles. Adobe brick sizes vary from small to large, but are typically 4 by 10 by 14 inches. To begin, wet the forms to minimize sticking. When pushing the mix into the form, start with the corners to make sure the the edges are well defined. When the form is filled, carefully lift it off. A few taps on the corners or shake may be necessary.