Civil Engineering Reference
In-Depth Information
Recipes for lime paint
The following recipes are well tested and recommended. Painting should be carried out in
damp periods, and the painted surface protected from direct sunlight for at least 14 days
after it is complete. The walls to be painted should be moistened beforehand with lime
water - part of all lime paint recipes. Lime water is made as follows:
1.
'Wet' slaked lime is mixed with water in a proportion of 1:5.
2.
The mixture is stirred well until all the lumps have disappeared.
3.
After 24 hours all the lime has sunk to the bottom. The water above the lime is lime
water. The layer of crystals that has formed on the surface must be removed. Lime
water is strongly alkaline, with a pH of about 12.5.
Lime milk is also an important ingredient in the paint. It is quite simply a dispersion of solid
slaked lime and lime water in the form of lime solution. A very fine-grained calcium hydrox-
ide with particles of about 0.002 mm arises through slaking. Lime milk is prepared in the
following way:
1.
Fresh 'wet' slaked lime is mixed with lime-water in a proportion of 1:5.
2.
The mixture is stirred well until all the lumps are removed. After about 10 minutes a
good lime milk is created. It can stand several days before use.
Lime surfaces rub off, but this can be retarded by adding a little sinew glue, see p.259
(Animal glues) to the lime solution. This method is only for use inside a building.
The pigments best suited for lime paint are ferric oxide colours: yellow, brown, red, black
and ultramarine, which tolerate lime. The pigments should be mixed with water and made
into a thick gruel.
Lime paint can best be directly applied onto completely fresh render, and there is seldom
the need for a second coat. Old, decayed render, or lime or cement paint, must be brushed
clean of dust and dirt if the paint is to bind properly. Lime needs several days to become prop-
erly bound to the surface. It is important that the render and the layer of paint do not dry out
during this period. In particularly dry weather, the wall should be watered when it feels dry,
especially if the sun is shining on it.
Recipe 1: White lime
The surface is painted with lime water, followed by two or three coats of lime milk, then
another coat of lime water.
Recipe 2a: Red lime
The earth pigment ferric oxide is soaked in two parts water overnight to become a pigment
pasta. The soaked pigment is then mixed with lime water in a proportion of 1:9, to become
a lime paint. The wall is first given a coat of lime water, then a coat of lime paint, and is
finished off with another coat of lime water.
