| 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. BACK
TO THE TOP 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.
BACK
TO THE TOP 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. BACK
TO THE TOP |
