Cover Image
close this book Village-Level Brickmaking
close this folder Appendices
View the document Appendix 1 - Clay Testing
View the document Appendix 2 - Making A Hinge Mould And Moulding Table
View the document Appendix 3 - The 3: 4: 5 Method
View the document Appendix 4 - Pyrometric Cones
View the document Appendix 5 - Woodlots
View the document Appendix 6 - References

Appendices

Appendix 1 - Clay Testing

Before beginning to make bricks for the first time, it is essential to know if the clay which you intend to use is the right type for making good quality bricks. Although brickmaking clays are abundant in many countries, not all villages have a supply of good quality brickmaking clay nearby. Before beginning to organize a brick production site, check very carefully that your clay is the correct type.


Figure

There are two ways you can check the quality of your clay. The first is to contact a soil technician who can have your soil tested in a laboratory (check with the local public works office for the location of the nearest laboratory). The results of the test are usually quite accurate and can be very informative if they are interpreted well.

The second method is to test the soil yourself, using simple field tests that require no special equipment. These tests are usually quite satisfactory but occasionally the results of these field tests can be misleading if you have no experience in brickmaking or soil testing since some interpretation is required.

The basic information which you must get from any set of tests should answer the following questions:

1. Can the clay be prepared easily and moulded into the shape you want?

2. Can the moulded clay brick dry without cracking or breaking?

3. Can the clay brick be fired to a very high temperature without cracking, breaking or distorting?

4. Will the fired brick be strong and suitable for use in construction?

5. What is the total shrinkage of the clay after firing? What should the size of the mould be?

Collecting Samples for Testing

In order to do any soil testing, whether it is done in a laboratory or in the field, you will have to collect samples of the soil which you wish to test. Before digging, clean an area of about one square metre, removing all leaves twigs, grass, and stones. Start digging through the first 300 to 500 mm of soil which contains roots and dead leaves. This layer is called top soil and is never used for brickmaking. Remove this layer completely. The soil sample is taken from the layer underneath.


Figure

If the soil is to be analyzed in a soil laboratory or if it is to be transported to another village for an experienced brick maker to test, you will need to provide them with at least 50 kg of each soil sample. Put each soil sample into a separate strong sack. Do not mix them together. Each sack should be identified with a tag with the following information:

1. Your name,

2. The address where you can be contacted,

3. A description of the location of the clay giving as much detail as possible. For example: clay was dug 20 metres from the banks of the N'komati River in a maize field 2 kilometers west of the village of Nanrapa The sample was taken from a hole one metre deep, 50 metres from a large mango tree. A description like this is very important if you have more than one sample and it may be necessary to draw a map of the area showing all your test sites. (If you have many samples, it is a good idea to identify both the sample and the pit with numbers.)

Be sure to put a copy of the identification card inside the sack with all the information in case the outside tag is lost or destroyed. Keep a detailed record for yourself of where you dug each sample.

Good brickmaking clays are made of a certain combination of clay and sand. If the clay content is too high (as in the clay used for pottery), the brick will crack and break while drying. If the sand content is too high, the brick will be weak and break easily.

Important: Soils can change completely over a small area. If you find a suitable clay, be sure that it is not an isolated pocket and that there is sufficient clay to continue to make bricks for many years.

Simple Field Testing of Clay Samples

Simple, basic field testing can be done on site to test a clay's suitability for brickmaking. The simple tests listed here will give you only a very general idea about the suitability of your soil. They are not as accurate as laboratory tests and should not be used as a substitute. However, they can help you to quickly rule out poor brickmaking clays and to identify clays with brickmaking potential.

Test 1: Moulding

Take a handful of dry clay soil and begin mixing it with a small amount of water until it becomes soft and malleable. Do not add too much water as this will make it too soft and wet. Try making different shapes with the clay.

The objective of this test is simply to see if the soil can be moulded easily and to get an indication of how difficult it may be to prepare the soil for brickmaking.


Figure

If it is difficult to make any shape with the soil or if it keeps falling apart, the soil can not be used to make bricks because it probably contains too much sand. If the soil holds its shape and can be moulded easily, continue with the following tests.

Test 2: Forming and Drying Clay "Eggs"

With the moist soil, mould it into a form about the size and shape of a chicken's egg. Make 20 to 30 of these "eggs" and leave them in the sun to dry. After about a day or two, check the "eggs" to see if they have cracked or broken apart.

If they have large cracks, the soil probably has too much clay and is not suitable for making bricks. This particular soil may need to have sand added to it in order to stop the cracking. It will be necessary to experiment with different proportions of sand and soil to determine the correct ratio.

If they did not crack apart or if they have only very small cracks, try crumbling or breaking them in your hands. If they crumble easily, it probably means that the soil has too little clay in it and is unsuitable for making bricks. If they do not break or crumble easily, the soil has a potential for brickmaking.


Figure

Test 3: Firing Clay "Eggs"

Take a number of the "eggs" that are very dry and have no cracks and put them into a small fire. Keep the fire small for the first thirty minutes and then make a large hot fire. Try to keep the fire hot for at least two hours or longer if possible. At the end of the firing, the "eggs" should be well covered with hot ashes and left to cool until the next day. When cool, examine the clay "eggs" and try crushing them with your hands. If they crumble easily, the soil is probably not suitable for fired bricks. If they do not crumble easily, the soil has potential for brickmaking.

Place a few of the fired clay "eggs" in a bucket of water and leave them overnight. By the next day, if they have dissolved or feel soft, they were either underfired or the soil is not suitable for brickmaking. (This is a problem with field tests like this; without controls you do not know if the clay "eggs" or bricks were fired correctly or not.) Try crushing a few of the clay "eggs" that were left underwater. If it is difficult, the soil is probably suitable for brickmaking but further testing should be done.


Figure

Test 4: Making a Brick

If the previous three tests indicate that the soil might be suitable for brickmaking, continue and make a full size brick. If you do not already have a mould, make an experimental hinge mould with internal dimensions approximately 7% larger than the desired size of the finished fired brick. (See Appendix 2 for detailed information on making a hinge mould.) With the soil which has shown the most potential for brickmaking, make 50 or more bricks using the hinge mould. Follow the directions given in the manual for moulding and drying the bricks.

When dry, build a small kiln with the bricks and fire it over a 24 hour period, trying to follow the same procedures as described for a large scale kiln. After cooling, examine the bricks carefully and note if the bricks are cracked, broken, or if they appear to be weak or strong.

(See the section on Problem Bricks, page 80-81.) If you are satisfied with the results, continue to use the same clay on a slightly larger experimental scale and produce enough bricks for a 1,000 brick kiln. Fire this kiln and once more note the results.


Figure

Appendix 2 - Making A Hinge Mould And Moulding Table

Before beginning to make the hinge mould you must determine two things. First, what will be the final fired brick size and second, how much does the soil shrink from its moulded to its fired brick state.

Read the chapter on Standardization for information on the best sizes for bricks. Once the fired brick size has been decided, the interior dimensions of the mould can be calculated.

Remember that all brick clays shrink between 5% and 11% when dried and fired. Therefore to arrive at the correct size of brick, the moulds must be 5% to 11% larger than the final size of the brick.

The best way to determine the shrinkage rate for a particular clay is to have a soils laboratory do the testing. This is important especially if the bricks must be produced to a specific dimension. If the final size is not that critical and an error of 5 to 10mm in overall length is not a problem, then the following method can be used to determine the shrinkage rate for a particular brick clay.

1. Make an experimental hinge mould and follow test 4 in Appendix 1. Make 50 or more bricks and fire them in a small kiln.

2. Once fired, randomly select 10 unbroken bricks.

3. Lay the 10 bricks butted up tight against each other, end to end, on a smooth level floor.

4. Measure the overall length of the bricks in millimetres and divide that length by ten. This will give the average length of the bricks.


Figure

5. Measure exactly in millimetres the inside length of the mould used to make the bricks.


Figure

6. Use the following formula to determine shrinkage rate.

% of Shrinkage =((length of mould in mm) - (average length of bricks)) x 100/(length of the mould in mm)

For example: length of the mould = 258mm average length of bricks = 240mm

% of Shrinkage =(258 mm-240 mm)x100/258mm= 18x100/258= 1800/258=7

Shrinkage = 7%

The following table shows, the interior mould sizes for various shrinkage rates to make four different sizes of fired bricks. For example, a village would like to produce a fired brick 240mm x 115mm x 73mm in size and knows that their clay has a shrinkage rate of 8%. In order to obtain that final size, the interior of the mould must be 261 mm x 125 mm x 80 mm.

Table For Interior Mould Sizes

Fired Brick Size: 240 mm x 115 mm x 73 mm

Interior Mould Size

Shrinkage

length

width

height

5%

253 mm

121 mm

77 mm

6%

256 mm

122 mm

78 mm

7%

258 mm

123 mm

79 mm

8%

261 mm

125 mm

80 mm

9%

264 mm

126 mm

81 mm

10%

267 mm

128 mm

81 mm

11%

270 mm

129 mm

82 mm

12%

273 mm

131 mm

83 mm

Fired Brick Size: 230 mm x 110 mm x 70 mm

Interior Mould Size

Shrinkage

length

width

height

5%

242 mm

116 mm

74 mm

6%

244 mm

117 mm

75 mm

7%

247 mm

118 mm

76 mm

8%

249 mm

120 mm

77 mm

9%

252 mm

121 mm

78 mm

10%

255 mm

122 mm

78 mm

11%

259 mm

124 mm

79 mm

12%

262 mm

125 mm

80 mm

Fired Brick Size: 220 mm x 105 mm x 66 mm

Interior Mould Size

Shrinkage

length

width

height

5%

232 mm

110 mm

69 mm

6%

234 mm

112 mm

70 mm

7%

236 mm

113 mm

71 mm

8%

239 mm

114 mm

72 mm

9%

242 mm

115 mm

73 mm

10%

244 mm

117 mm

73 mm

11%

247 mm

118 mm

74 mm

12%

250 mm

119 mm

75 mm

Fired Brick Size: 210 mm x 100 mm x 63 mm

Interior Mould Size

Shrinkage

length

width

height

5%

221 mm

106 mm

66 mm

6%

223 mm

107 mm

67 mm

7%

225 mm

108 mm

68 mm

8%

228 mm

109 mm

69 mm

9%

231 mm

110 mm

69 mm

10%

233 mm

111 mm

70 mm

11%

236 mm

113 mm

71 mm

12%

239 mm

114 mm

72 mm


Figure


Figure


Figure

Appendix 3 - The 3: 4: 5 Method

The 3:4:5 method is a simple way to ensure that corners are right angles or 90 and can be used when laying out a building or field kiln.

The 3:4:5 rule states that when a triangle has one side (AB) 3 units long, another side (BC) 4 units long, and the hypotenuse (AC) is 5 units long, the angle ABC will be 90 or a right angle.


Figure

This method requires that you use some unit of measurement. This unit could be the length of your foot, the distance between two knots tied in a string, or a length of one metre as measured on a tape measure. The length of the unit can be anything you choose but you will find that a unit measurement of one metre is ideal for marking the corners of a field kiln.

For example, if a triangle has one side 3 metres long, another 4 metres long and a hypotenuse 5 metres long, the angle ABC will be 90 or a right angle. This rule also holds true if the measurements are multiples of 3:4:5, such as 6 metres: 8 metres: 10 metres or 9:12:15.

Example: Laying out a corner of the field kiln

1. Select your unit of measurement which should be one metre or more in length. The most accurate method is to use a 5 metre tape measure. Note: If you do not have a tape measure, make one with a long piece of cord or string. First tie a knot close to one end of the cord and holding the knot in one hand, stretch your other arm out as far as possible as shown in the diagram. Tie a second knot at that point on the cord. For most people this distance is about one metre. Hold the second knot and measure that same distance again and tie a third knot. Continue until you have six knots with equal spaces between them. The distance between the first and last knot will be 5 units or approximately 5 metres.

2. Mark the first side of the kiln. Drive a large nail or spike into the ground where the comer of the kiln will be. Tie a string to the spike and stretch the string in the same direction as the length of the kiln (the side with the tunnel openings). Fix the string in this position. Using a tape measure (or the cord that was made to measure units), measure four metres from the comer along the string and drive another spike into the ground at that point.


Figure

3. Mark the second side of the kiln. Tie another string to the first spike (where the corner will be) and stretch it out in the direction of the kiln width (the side without tunnel openings). Using a tape measure or measuring cord, measure 3 metres from the corner along the string and tie a knot in the string at that point.


Figure

4. Mark the hypotenuse. Attach another string to the spike that marks the 4 metre point on the first side. Measure 5 metres on this third string and tie a knot. This string will form the hypotenuse of the triangle.

Stretch the knot on the 5 metre string towards the knot on the 3 metre string. Move both strings until the 5 metre knot and the 3 mete e knot are exactly on top of each other. Both strings should be taut.


Figure

5. Fix the 3 metre string in this position and the 5 metre string can be removed.

If you have followed all the steps and measured accurately, the angle or corner formed by the 4 metre string and the 3 metre string should be 90 or a right angle.

Appendix 4 - Pyrometric Cones

A pyrometric cone is a cone made of a ceramic material that will deform or bend when a predetermined temperature is reached. It is used to measure the temperature in a back kiln. Each numbered cone corresponds to a known temperature at which it will deform. The two most common names or manufacturers of pyrometric cones are Orton and Seger. They both use a similar numbering system but the temperatures that correspond to those numbers vary slightly. The table on pyrometric cones listed here gives only some of the available cone numbers and corresponding temperatures.


Figure

PYROMETRIC CONES

CONE NUMBER

TEMPERATURE DEFORMS

 

SEGER

ORTON

014

815C

830C

013

835C

860C

012

855C

875C

011

880C

895C

010

900C

905C

09

920C

930C

08

940C

950C

07

960C

990C

06

980C

1015C

05

1000C

1040C

04

1020C

1060C

03

1040C

1080C

02

1060C

1125C

01

1080C

1145C

1

1100C

1160C

When building the field kiln, spaces (called spy holes or peep holes) are left, about 1 metre in length, 80 mm wide and 120 mm high. The cones are placed at the end of these holes and a brick "plug" covers the outside. The brick plug can then be removed during the kiln firing for observing the cones and estimating the temperature of the kiln at that particular place.

Normally three different cones are placed in each of the spy holes. These cones are usually embedded in a fireclay base to prevent them from falling over and then the whole unit is placed at the end of the spy hole. One of the cones is a number that will deform when the correct temperature (usually 950C) is reached. Another cone is a number that will deform at a slightly lower temperature; this will warn you that the firing is almost complete. The third cone is a number that will deform at a temperature higher than 950C; this will inform you that the kiln has been heated beyond the desired temperature and the bricks are likely to be overfired.

For example, using Orton Cones, cones N 010 08 and 06 are placed together inside the spy holes of the field kiln (each spy hole will get one set of these cones). Cone N 010 will deform at a temperature of 905 C. Cone N 08 will deform at 950 C (usually the correct temperature for firing bricks) and cone N 06 will deform at a temperature of 1015 C.


Figure

The cones are set at a slight angle in a special clay base. When the temperature of the kiln in the area of this set of cones reaches approximately 900C, the first cone (no. 010) will begin to deform. When the second cone (no. 08) begins to deform, the kiln in that area has reached the correct temperature for firing bricks and this temperature should then be maintained for 12 to 24 hours. If the third cone (no. 06) begins to deform, the kiln has passed the desired temperature and there is a risk of overfiring the bricks.


Figure

Pyrometric cones come in two sizes; either 30 mm or 50 mm tall and are sold in boxes of 50. When buying the cones, always specify the type of cone (Segar or Orton), the size (30 or 50 mm) and the number of the cone with its corresponding temperature.


Figure

Pyrometric cones are ideal, especially when firing a field kiln for the first time. They provide valuable accurate information and do not require the brickmaker to have experience in estimating the temperature of the kiln by observing the colours of the bricks inside the fire tunnels. They are also excellent training tools because the fret-time brickmaker can learn by relating the colours seen in the kiln to the information gained from the cones and then use this experience in the next kiln firing.

Appendix 5 - Woodlots

Wood should only be used for firing bricks if your area has a plentiful supply of firewood and no coal or alternative fuel. Brickmaking uses such large quantities of firewood that its use could mean less firewood for cooking in the village, or even lead to deforestation. Because there are few areas with forests that can supply industry as well as for domestic use, every brickmaking unit should establish a woodlot to supply their needs and not depend on the existing forests.

One major advantage of firewood over coal or oil is that it is renewable. Using firewood for brickmaking does not have to lead to deforestation if the producer takes care to either match production to the capacity of the forest to supply fuel, or if the brick producer establishes woodlots to supply their own fuel.

If you own or are a member of a brick production unit, you have a responsibility to the community not to deplete the supply of firewood which is used for domestic use or to cause deforestation. An average family of four uses at least one cubic metre of firewood per year. If a brickmaking unit was established that produced even 20,000 bricks per year, the amount of firewood needed would be equivalent to the firewood used by 60 new families moving into the village.

Because there are so few areas with forests that can supply firewood for domestic use as well as brickmaking, it will be essential for you to establish a woodlot. There are certain trees such as eucalyptus that are very fast growing and can produce more than 20 times the annual growth of a natural forest. Well managed woodlots can yield from 25 to 60 m3 of firewood per hectare per year. (one hectare = 10,000 m2 or 2.471 acres.) In comparison, a natural forest may yield only 2 to 8 m3 of firewood per hectare. However, there will be a delay, from 4 to 8 years, between planting the trees and harvesting them.

The amount of land required for the woodlot will depend on the amount of fuel needed to fire the kilns. If you were to fire 20,000 bricks per year, requiring 60 m3 of firewood per year, you would need a woodlot of approximately 2 hectares with an annual yield of 30m3 per hectare to supply your needs.

The following is a list of issues to consider and steps that a village brickmaking unit will have to go through to establish a woodlot.

Purpose of the Woodlot

The first and most important decision that must be made by the management of a brick unit or the membership of a brick cooperative is: What is the purpose of the woodlot?

- is it to supply only the needs of the brick unit?

- or should it also produce enough to supply cooking fuel for the village?

- if the brick unit will grow trees for fuel, will it also grow trees for food (e.g. fruit trees) or for windbreaks and erosion control?

If this fundamental decision is made, it will simplify the rest of the decision making that must be done and will help those who will advise the brickmaking unit. Once this decision is made, a small group of people should be appointed to investigate and obtain information on how to establish a woodlot.

Contact Local Officials and Government Departments

The next step is to start to contact local officials and government departments to discuss your decision to establish a woodlot. They will be able to give you most of the essential information and advice that you will need.

Local officials might include village presidents, head men, chiefs, district administrators and district development officers. Government departments that should be approached are agriculture, the department responsible for assigning land and most importantly, the local forestry department. They will all be able to advise and support the project in a number of ways.

Choosing a Site

There are many factors to consider when deciding where to place the woodlot. Most importantly,

- it should be as near as possible to the brick site to decrease the expense of transport.

- if the woodlot is also to produce fuel for the village, it should be situated relatively near to the village.

- it is also very advantageous if it can be located in an area where the forestry department is active and involved in afforestation.

- the site should not be located in an area that is used for grazing or other agricultural purposes.

- it is also best if the site is relatively flat with good soil;

- has a sufficient supply of water all year; and

- has good road access to and within it.

- if you are to also start a nursery, there should be an adequate and continuous supply of water to water the seedlings; and

- there should be protection against extremes of climate such as heat, frost, hail, and wind.

- also check the ownership of the land early in the planning stage.

The size of the site will depend on:

- the amount of firewood needed each year,

- the yield of the woodlot per hectare,

- the number of trees that will be planted each year and

- how long it will take before harvesting can begin.

The organization of the site should take into consideration how the trees will be cut and moved and how the timber (if any) will be sold.

Cooperation with the Forestry Department

Cooperating with the local forestry department will greatly benefit any brick making unit that plans to establish a woodlot. They are experts in the field and will be able to supply invaluable information and advice. Often forestry departments have special projects that work exclusively with groups establishing village woodlots.

The forestry department will be able to give you information on:

- the types of trees to plant given the soil and rainfall in your area,

- nurseries in the area,

- the costs involved in starting and running a woodlot,

- how much labour is needed

- how to organize your labour,

- how to protect the trees from animals,

- the equipment needed,

- the number of trees to plant,

- where to place and clear the site,

- how to establish a nursery (if necessary),

- when to sow the seeds since seedlings must be of the right size by the start of the planting season,

- how to plant the seeds (in seedbeds, in individual containers, in planter flat trays or in empty beer or soft drink cans cut in half),

- when to plant the seedlings,

- how to care for the trees, and

- how to harvest.

- they will likely also be able to assist in any staff training.

Appendix 6 - References

Bawa, N.S., Manufacture of Burnt Clay-bricks In Wood-Fired Clamps, Technical Paper No.

6, Building and Road Research Institute, Kumasi, Ghana, 25p.

Beamish, A. and W. Donovan, Fabricacao de Tijolos, Technical Manual, Direccao Provincial De Construcao e Aguas, Cabo Delgado, Mocambique, October 1985, 68p.

, Forno de Empilhamento, Como Construir e Queimar, Technical Manual, Direccao Provincial de Construcao e Aguas, Cabo Delgado, Mocambique, May 1985, 55 pp.

, Ensaios de Barro, pare a Fabricacao de Tijolos Queimados, Technical Manual, Direccao Provincial de Construcao e Aguas, Cabo Delgado, Mocambique, January 1986, 54 pp.

Donovan, W., Brickmaking Field Notes - Abyei Sudan, unpublished field notes for The Harvard Institute for international Development, Cambridge, Mass., April 1981.

Gulick, S., Brick and Kiln Notes, unpublished field report for Harvard Institute for international Development, Cambridge, Mass., April 1979.

International Labour Office, Small-Scale Brickmaking, Technical Memorandum No. 6, 1984, 210 pp.

Lay, M. C. D. and A. Reis, Utilizacao de Tijolos, Technical Manual, Direccao Provincial de Construcao e Aguas, Cabo Delgado, Mocambique October 1984, 100 pp;

Parikh, J.K., "Planning of Rural Energy Systems: Issues and Perspectives", Appropriate Industrial Technology For Energy For Rural Requirements. United Nations Industrial Development Organization,pp. 119-140.

Parry, J.P.M., Brickmaking in Developing Countries, Garston, Watford, British Research Institute, 1979, 88pp.

Smith, R.C., "Improved Moulding Devices for Hand-made Bricks", in Appropriate Technology, London, Intermediate Technology Publications, 1981 Vol 7, No. 4.

Svare, T.I., Better Burnt Bricks, Technical Pamphlet No. 1, Dar-es-Salaam, National Housing and Building Research Unit, 1971.

Thomas, D.W., Small-scale Manufacture of Burned Building Brick, Arlington, Virginia, Volunteers in Technical Assistance, 1977.

Turner, T., "Appropriate Technology For Rural Energy Supply In Developing Countries", Appropriate Industrial Technology For Energy For Rural Requirements, United Nations Industrial Development Organization, pp. 27-101.

Technical information for the chapter on how to build and fire a brick kiln with coal was provided by Michael Parks and John Spiropoulos of Intermediate Technology Development Group, Rugby, U.K.