Applying
limewash to new lime renders or lime plasters
Generally limewash should be applied thinly and be allowed to dry out slowly.
Mike Wye 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. Mike Wye 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.
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 are recommended on new external lime render, three coats
on new internal lime plaster. Ideally leave each coat to cure
for a minimum of a couple of days. 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.
Advice and information is given in good faith. It's important
that users satisfy themselves that they've chosen an appropriate
product and have a suitably skilled workforce.
Applying limewash 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
- 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.
- This may involve two or three sprayings, some ½-1
hour prior to limewashing to soak well into the surface and
a top up a few minutes prior to limewashing.
- 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.
- It may be prudent to test how well this first coat has bonded
on a trial panel before proceeding to additional coats.
- Ideally leave each coat to cure for a minimum of a couple
of days 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:
- Additives in the original limewash such as tallow or raw
linseed oil, which reduce the porosity and hence the key for the
new limewash.
- Surface dusting or chalking, which may detract from a sufficiently
consolidated surface for the new paint to key onto.
- 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.
- 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.
- Applying in low temperatures or when there's a risk of frost.
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