For the manufacturing of lime milk, the well-matured, wet-slaked Rødvig slaked lime is mixed with lime water in a strongly attenuated solution, approx. 1 part lime putty : 5 parts lime water for a lime solution of approx. 15%, which should not be exceeded. The lime putty is stirred thoroughly with the limewater in a tub by using e.g. a drilling machine with a whisk attached. The lime milk should be prepared at least 24 hours before use and stored in plastic buckets with hermetic lids. The purpose of the lid is to stop the passage of the air and thereby a quick hardening on the surface in form of a layer of lime crystals CaCO3.
Mixing the lime milk with pigment
Pigment powders for lime milk should be lime-proof and fast. They are soaked in limewater, approx. 1 part pigment powder for 1 part limewater, at least 24 hours before use. By using e.g. lids, you stop the passage of air. The soaked pigment pasta must be blended before it is measured, and mixed with the stored stirred lime milk. The mixed whitewash (lime milk) is known to be able to carry up to 10% pigment powder without any significant smudging. There is no space for more pigment grains between the lime crystals. Therefore, coloured lime will never have a very dark pigment. It may be a good idea to glaze with coloured lime water with the same colour pigmentation as the desired coloured lime milk. The glazing also serves as a constant base colour, and when the base colour is the same as the coloured lime milk, the colour of the base will not appear grey and boring, even after wear and tear. Before the coloured lime milk is mixed, you should always do test-mixing and test-coating. After the surface has dried, it can be determined whether the pigments are right or if they should be changed. Always remember to note down the mixing ratio. As mentioned earlier, you must never put more than 10% pigment powder in the lime milk. It is therefore recommended that you dose less than 10%. Experiences show that approx. 7% is usually sufficient. You can begin with 3 different dosings:
100 cl. applicable lime milk: 10 cl. pigment pasta (10%)
100 cl. applicable lime milk: 7 cl. pigment pasta (7%)
100 cl. applicable lime milk: 3 cl. pigment pasta (3%)
Once you have chosen your dosing, the large amount is mixed after the same principle. You should always mix enough for the mixture to be able to cover the entire wall, i.e. from corner to corner, all the way up and down.