Clay soil must be able to show several properties to be used for brickmaking.
Clay soils are compounds of silica and alumina. Calcareous clays have calcium carbonate and will burn to a yellow or cream color. Non-calcareous typically contain feldspar and iron oxides, and will burn to a brown, pink or red, depending on the amount of iron oxide.
The silica in the clay, when fired at 900-1200 degrees C, will turn to a glassy phase. This process, called vitrification, will turn the clay to a crystalline structure. Therefore, temperature is important. If under-fired, the bonding between the clay particles will be poor and the brick will be weak. If the temperature is too high, the bricks will melt or slump.
Vitrification does not have to be complete, and does not actually occur in many of the small traditional brickmaking plants around the world. However, the vitrification does occur enough to give sufficient strength to the brick.
It takes approximately 3 m3 of clay soil to make 1000 bricks.
There will need to be enough water for the clay, a source of water must be available during brick production. Therefore, a source that is not present the entire year (for example, only during rainy season) will limit the brick production.
Also, the brickmaking production should not be in competition for water with other users. If a water source is a communal source, the water needed for brick production can take away from the other uses of water, such as drinking and cooking, washing, livestock watering and other domestic uses. It takes approximately 600L of water to produce 1000 bricks. A convenient method of storage is to use 3-200L drums.
Sand can be used to make minor adjustments to the quality of soil-it can be added to soil when drying to prevent the soil from becoming too brittle. Sand is also be used as a stabilizer in a mixture. An important use of sand is in the brickmaking process, where it is used to keep the bricks from sticking to the molds.
If no sand is available in a location where brickmaking is going to start up, sawdust, ash and fine dry soil can also be used to keep the clay from sticking to the mold.
Firewood and coal are the most common fuel sources used for firing bricks.
Coal waste from a power plant is the easiest coal source to use, if available in the area. For 1000 bricks, it takes 1 and 1/8 sacks of coal and 1/2 sack of cinder.
Approximately 3 m3 of firewood is needed to fire 1000 bricks. Since so much firewood is needed, there is a risk of denuding a natural forest and depleting a family's supply. On average, only 2 to 8 m3 of firewood per hectare per year is available in a natural forest. In a well managed woodlot, 25 to 60 m3 of firewood can be produced annually in the same area. There are also other advantages to woodlots, such as another food source, use as a wind break and erosion protection.
It is recommended that a brick production of 1000 bricks per day will require 600-1000 m3 of space.
Brick production requires transport for supplies and the finished bricks. Depending on the rate of production, frequent transportation will be required so there will need to be reliable tractors or trucks, etc. Also, access must be good for where the completed bricks will be transported.
The following is a sample list of tools and equipment recommended for a 15 person crew, working to produce 1000 bricks per day, taken from Village Level Brickmaking.
Brickmaking is labor intensive- it will be tedious and tiring. Workers, therefore, must be motivated to produce good quality bricks. Benefits may be in the form of fair salaries from the sale of bricks or benefit to the community. This may be in the form of better quality bricks that can be used to construct schools and clinics.
Although brickmaking may be considered a simple or low technology, good management is important for successful brick production. This includes providing an adequate supply of raw materials for the workers, keeping the equipment maintained and providing suitable facilities for the workers. It also involves checking the quality of the product regularly, setting up smooth flow of production and having adequate financial arrangements for purchases and salaries. Also, it is important to make sure there are skilled personnel, and that the workers have all the tools and information needed.
Assistance may be financial, technical or managerial. Financial assistance is needed at startup, as it may take 3-6 months of no earned income. Technical assistance can be used to improve clay preparation and molding, as well as firing the bricks. The local public works department can sometimes help with this. Finally, it is good to have a resource for questions about small business activities, such as development banks, government ministries or development organizations, as well as churches, schools and chambers of commerce.