Limewash Application
As a general rule, limewash should be applied in thin coats. It should never be used in wet or frosty weather or applied to a surface in direct sunlight on a hot day. IT will pay to do a trial patch, so that the consistency of
the wash can be adjusted if necessary.
Preparation of Surfaces
The surface to be limewashed should be free of all dirt, dust or lichen. If
mould is present, a fungicide should be used. Deep holes should be filled in
advance with lime mortar. The surface should then be dampened with water, so
that the moisture in the limewash will note be immediately sucked out. Porous surfaces need more damping down than hard stones.
THE FIRST COAT:
Dilute 50% lime wash to 50% water brush the limewash onto the dampened area, paying particular attention to the cracks and joints. Do not let it build up into a thick layer at these points.
SUBSEQUENT COATS:
Dilute 65% lime wash to 35% water, allow the previous coats to dry out completely, leave overnight.
Lightly damp down the previous coat before applying the next. At least three coats should be applied in all. After the initial drying out, limewash will continue to strengthen for several weeks.
Types of lime available for use in the making of limewash:
QUICKLIME - Also called lumplime or burnt lime. Quicklime makes a long-lasting and good quality limewash. IT IS HIGHLY CAUSTIC IN THE PRESENCE OF MOSITURE. Do not store in a damp place. IT must be slaked before it can
be used.
PUTTY LIME - is ready-slaked for use. It is the consistency of toothpaste and is quite caustic. It may be stored safely and improves with age. It is the simplest and safest way to make good quality limewash.
HYDRATED LIME - Also known as bag lime. It comes in a powder form, ready-
slaked, and is available from, any builders' merchants. It is an inferior material and tends to cake if stored in a damp place. IT makes a poor
quality limewash with a short life and has a tendency to brush off.
TALLOW
Tallow is a hard clarified animal fat, used in conjunction with quicklime in the slaking process. A small amount will make an external limewash which will shed some rainwater in exposed conditions. It is not necessary for internal limewash.
RAW LINSEED OIL
Used with putty or hydrated lime to improve water-shedding properties instead of tallow.
PIGMENTS
To colour the limewash where desired. Usually supplied in powder form.
Making Limewash- with quicklime
N.B. THE SLAKING PROCESS INVOLVES THE USE OF HIGHLY CAUSTIC MATERIALS PROTECTIVE CLOTHING SHOULD BE WORN AND PROPER PRECAUTIONS TAKEN.
The proportions of tallow to quicklime in traditional mixes vary considerably.
Some typical mixes are:
1: 21 - Tallow : Quicklime down to 1:7 Tallow : Quicklime
1:11 - Linseed oil : Quicklime
Mixing is best done on 50kg batches, since it is difficult to stir in larger quantities. Break the quicklime into small lumps, add to 2-3 buckets of water in a galvanised container (a dustbin is ideal) and allow the lime to
slake. When the reaction is complete add water as required and stir until the liquid is of a thick creamy consistency, free from lumps. Add the tallow, which should have been melting in another container and is now a
transparent liquid. Add the colour pigment at this stage. Alternatively the tallow can be shredded into the water before quick lime is added.
Stir the lime and tallow well and add more water, if required. The mix should be allowed to stand for at least 24 hours; two or three weeks is preferable, if this is possible. During this time the mixture will separate
into a lime putty with lime water on the surface. Keep this liquid, as tit can be used later for thinning. The limewash must be screened through muslin to remove any unslaked lumps of lime. The final mixture should be diluted
until it is a milky consistency.
Using ready- Slaked Lime (Lime Putty)
Place the lime putty in the galvanised container and add water, stirring to a smooth paste with a whisk or similar instrument. Add more water until the mixture is thin and creamy. For hydrated lime, mix water with the lime to
form putty, following the manufacturers instructions, then add more water. Linseed oil can then be added; a mix of 1:11 Linseed oil: mixed lime is typical. Screen the limewash for lumps and add any colour pigment. Dilute
the mixture until it is a milky texture, and screen again. The limewash is now ready to use.
Colour
If coloured limewash is required, it is important to experiment with different pigments. Colour wash dries approximately 50% lighter than the wet colour. Some approximate mixes are:
CREAM: 4-6 lb ochre : 8 galls lime putty.
FAWN: 6-8 lb umber + 2 lb Indian red + 2 lb lamp black : 8 galls lime putty.
BUFF: 6-8 lb raw umber + 3-4 lb lamp black : 8 galls lime putty.
APRICOT: 14 lb raw sienna + 1 lb red ochre : 8 galls lime putty.
