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LIMEWASHING
on new lime renders or lime plasters
Limewash is the preferred finish on traditional buildings as it allows
the structure to "breathe", allowing any damp present to evaporate away
rather than be trapped in the wall. It has a matt finish and helps consolidate
and improve the surface of both old and new plaster physically and visually.
We supply a range of colours as well as white. Because limewashes are
porous paints they shade in depth of colour to reflect the dampness of
the background material.
Generally limewash should be applied thinly and be allowed to dry out
slowly. Our limewash is prepared from the finest quality lime putty slaked
from Buxton quicklime. It will develop a fine finish over several coats,
we recommend a minimum of four on new render and plaster. Our limewash
has a small quantity of linseed oil added to reduce "dusting" and improve
external water shedding. Historically, many ingredients were added to
limewashes to modify their performance such as common salt, casein, tallow
and linseed oil.
Preparation
The surface to be limewashed should be brushed and washed free of
any loose particles, dust, dirt, lichen etc. If there is mould growth
the surface should be treated with a fungicide ( e.g. a weak bleach solution)
which should be rinsed off before limewashing.
Damping
It is very important for dry surfaces but may not be necessary if
limewashing new lime render or lime plaster which has yet to totally dry
out. Spray the area before limewashing with water as this prevents the
water in the limewash from being sucked out too quickly on application.
This must be allowed to soak in from the surface or failure can occur
due to lack of suction.
First Coat
Please whisk the limewash thoroughly before use as the putty will settle
out. Brush the limewash onto the dampened area with a large emulsion
brush. Work it well into any cracks or joints but don't let it build up
too thickly as it can craze on drying out. Remember it's a wash and will
look transparent on application but will dry opaque. Coloured limewashes
dry to a much lighter shade than the wet limewash.
Subsequent Coats
Four coats ( five for white ) are recommended on new external lime
render, three coats on new internal lime plaster. Ideally leave each coat
to cure for a minimum of 24 hours. For each further coat, follow the same
procedure of misting well before limewashing and allowing to dry out slowly,
with light spraying if necessary. Protect external limewash from the weather
if necessary. A thin coat curing slowly in the presence of moisture will
form a more crystalline, hardwearing surface compared to a chalky finish
if a thick coat dries out too quickly. After the initial carbonation and
curing limewash will continue to strengthen for several weeks.
Frost
As limewash is a water-based paint, it shouldn't be applied in low temperatures
of less than 5ºC or if there's a risk of frost.
Quantities
A litre of limewash will cover 3 - 6 square metres for one coat, depending
on the smoothness and porosity of the surface being limewashed.
Safety
Limewash is caustic. Always wear eye protection and protective gloves
and clothing and follow the safety instructions on the labels.
Our advice and information are given in good faith. It's important
that users satisfy themselves that they've chosen an appropriate product
and have a suitably skilled workforce.
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LIMEWASHING
over old coats of limewash
Further to the general guidance above,"Using Limewash on new lime renders",
we would suggest the following points are noted
1. Remove flaking limewash with a stiff brush e.g. a churn brush to get
rid of loose material. As it is possible that chalkiness/dust on the original
limewash is reducing the quality of key of the new limewash its important
to make sure that the original surface is well wetted. Generally it easier
to ensure that the walls are adequately wetted with a spray rather than
a brush.
2. This may involve two or three sprayings, some ½-1 hour prior to limewashing
to soak well into the surface.
3. For the same reason of improving the key for the first coat, apply
this coat thinly. As we make a relatively thick limewash you can dilute
this first coat with a little clean water if necessary and ensure that
it dries out slowly. This may involve light spraying if necessary to slow
down the drying process where the background is especially "thirsty" or
the weather windy or hot.
4. It may be prudent to test how well this first coat has bonded on a
trial panel before proceeding to additional coats.
5. Ideally leave each coat to cure for a minimum of 24 hours. For any
further coats, follow the same procedure of misting well before limewashing
and allowing to dry out slowly, with light spraying if necessary. Protect
external limewash from the weather if necessary. A thin coat curing slowly
in the presence of moisture will form a more crystalline, hardwearing
surface compared to a chalky finish if a thick coat dries out too quickly.
After the initial carbonation and curing a limewash will continue to strengthen
for several weeks.
If adding casein into a limewash, mix the casein with some warm water
first. Always add water to powder and slowly whisk to form a paste and
leave to stand for 30 minutes. Slowly whisk in more water until a similar
consistency as the limewash is achieved. Leave to stand for a further
15 minutes and then whisk well into the limewash.
Poor bonding of a new limewash onto an existing limewash can result from:
1. Additives in the original limewash such as tallow or raw linseed oil,
which reduce the porosity and hence the key for the new limewash.
2. Surface dusting or chalking, which may detract from a sufficiently
consolidated surface for the new paint to key onto.
3. Applying the new limewash too thickly. Our limewash is already relatively
thick and easy to apply with or without added casein and must be applied
thinly.
4. Over rapid drying caused by insufficient damping down prior to limewashing
or insufficient slowing down of the drying process e.g. by spraying or
physical protection.
5. Applying in low temperatures or when there's a risk of frost.
6. Over enthusiastic application of water before application of lime or
application of lime too soon after damping down as this stops the suction.
Safety
Limes are caustic. Always wear eye protection and protective gloves and
clothing and follow the safety instructions on the labels. Our advice
and information are given in good faith. It's important that users satisfy
themselves that they've chosen an appropriate product and have a suitably
skilled workforce.
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LIMEWASHING
onto Masonry & Emulsion paints
Further to the general guidance above "Using Limewash on new lime renders",
we would suggest the following points are noted.
Please note the safety precautions on the tubs and protect eyes and skin
.
It is difficult to limewash onto surfaces painted with masonry or vinyl
emulsion paint and is always best remove other types of paint before limewashing.
There are a number of factors to be considered.
1. The previous paint system may not be very porous, and the benefits
of the limewash are therefore aesthetic rather than letting the building
"breathe". Because the background material isn't necessarily porous the
limewash, isn't able to soak into the pores of the material. Instead it
will tend to sit on the surface. This will make it prone to flaking or
weathering at a faster rate than usual. This can be very rapid in some
cases.
2. A sample area should be tested to judge adhesion of the limewash, the
ease of painting and the degree of coverage achievable with two or three
coats.
3. It may be necessary to add ingredients to the limewash to improve its
adhesion and durability. Traditionally both casein (from skimmed milk)
and common salt have been added. There are also a number of old recipes
using various sources of albumin, such as egg white, milk, blood and plant
seeds. Albumin is a simple protein that combines with slaked lime to produce
hardening properties. We have used and supplied a casein paint as an additive
at the rate of 0.5-1kg of casein paint to 20 litres of limewash and this
has improved adhesion in several cases. It is also possible to gauge in
some natural, breathable emulsion.
If adding casein into a limewash, mix the casein with some warm water
first. Always add water to powder and slowly whisk to form a paste and
leave to stand for 30 minutes. Slowly whisk in more water until a similar
consistency as the limewash is achieved. Leave to stand for a further
15 minutes and then whisk well into the limewash.
4. Preparation is very important; the surface to be limewashed
should be brushed and washed free of any loose particles, dust, dirt,
lichen etc. If there is mould growth the surface should be treated with
a fungicide (e.g. a weak bleach solution) which should be rinsed off before
limewashing.
5. Alternatives
For painting onto emulsions or gypsum plasters we supply casein paint,
clay paint, interior silicate paint and natural emulsions which will adhere
well to these less porous surfaces. Casein has a deep matt and very slightly
chalky finish and is best suited where the background is dry and there's
low condensation. All the paints can be supplied pre-coloured or can be
mixed with a wide range of pigments to give a wonderful range of colours.
For external use we supply a silicate masonry paint to which a wide range
of pigments can be added to make a fabulous range of colours.
Safety
Limewash is caustic. Always wear eye protection and protective gloves
and clothing and follow the safety instructions on the labels.
Our advice and information are given in good faith. It's important that
users satisfy themselves that they've chosen an appropriate product and
have a suitably skilled workforce.
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