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

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