Building with earth - Gernot MINKE (1)

6 kg of tallow (melted suet) is poured into
– rye flour glue (15 litres of rye flour boiled
36 litres of water. This mixture is stirred care-
in 220 litres of water with the addition of
fully (care has to be taken because the lime
some zinc sulphate),
reacts very intensely with water and may
– agave juice,
splash and burn the skin). After adding 6 kg
– boiled banana leaf juice,
of kitchen salt and carefully stirring, this mix
– juice of the cactus opuntia,
should be allowed to stand for 24 hours in
– juice of euphorbia lactea,
a not-too-cold environment. The water layer
– kapok oil
that forms on the top of the mixture is
– raw and double-boiled linseed oil.
decanted. The pasty mix that remains is
then mixed with 3 kg of fine quartz sand
Cellulose glue paint
and applied with a brush in 3 to 5-mm-thick
Since it is very cheap, cellulose glue mixed
layers to the wall (Manandhar, 1983). This
with chalk powder is often used for painting
coating requires several weeks to cure. In
interiors. However, it offers little weather
Nepal, it is said to last for four to six years.
resistance. Its wipe resistance is also low.
A similar recipe was used successfully in
Australia (Department of Housing, 1981).
Tests performed with this mix at the Building
Research Laboratory (BRL) showed that
it bonds well with a rough, lean loam plas-
Bitumen coating
Bituminous emulsions offer good weather
protection for exterior walls. The following
recipe was successfully tested at the Central
Paint
Without
Linseed oil
g/m 2
0
400
kg/m 2 h 0.5
9.5
0.0
ter. But with a rammed earth surface made
Building Research Laboratory (CBRI), Roor-
Lime-casein 1:1
420/350
0.6/1.5
0.6hr/6–24hrs
of clayey loam, parts of the coating became
kee, India: 1 part of bitumen 80 /100 is heated
Lime-Casein 1:8
300/300
0.7
detached over a period of several months
in a container with 2 parts of naphtha. This
Silin-paint (van Baerle)
700/250/310
0.3
due to rain and frost, probably because the
bond between the coating and the ground
was insufficient.
Other stabilised lime washes
Several old text sources claim that in addi-
mix is then applied with a brush to a dry
loam surface. After this coating is dry, a
second layer is applied. In order to protect
the black surface thus formed by the sun, a
final coating of lime is recommended, which
is made of 70 g of animal glue mixed into 1
Hydrophob (Herbol)
Baysoline LD (Bayer)
Syltrit (Metroark)
BS 15 (Wacker)
Steinfestiger H (Wacker)
390/390
400/290
350/320
450/430
290/290
0.0
0.2
0.0
0.1
0.0
tion to mixing hydraulic lime into whey, it
kg of hydraulic lime dissolved in
12.2
can also be mixed into urine. Weiss (1963)
0.5 litres of water (Jain et. al., 1978).
found that using Kaolinite clay, strength
could be increased by adding urea and
Vapour diffusion
ammonium acetate. This practice was also
Coatings can significantly reduce the vapour
common in ancient China, where extremely
diffusion of walls. It should be remembered
thin porcelain was produced by adding
that in cold climates, the vapour barrier
putrefying urine to the mix.
According to Jain et al. (1978), the addition
effect of these coatings should be less on
the outside than on the inside.
12.3
of 70 g of animal glue dissolved in 0.5 litre
The vapour diffusion properties of paints
of boiling water and mixed with 1 kg of
available on the market are not mentioned
hydraulic lime proved good.
in their packaging, so experience is impor-
In Auroville, India, the following coating was
tant in judging their characteristics. Results
used successfully for mud brick domes: the
of tests conducted by the BRL made with
whites of 60 eggs mixed with 2 litres of
several paints, coatings, water-repellent
buttermilk and 5 litres of palm liquor stirred
plasters and water repellents are shown in
and mixed with 40 litres of shell lime and
12.1.
4 litres of cement (Pingel, 1993).
According to various sources, the following
Water penetration
plant matter added to the lime also en-
The capillary water intake (see chapter 2,
hances wipe and weather resistance:
p. 27) of loam surfaces is significantly influ-
100
Weather protection