Click on the links below to jump to the appropriate limewash guidelines.
- Limewashing on new lime renders or lime plasters
- Limewashing over old coats of limewash
- Limewashing onto masonry & emulsion paints
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 moisture present to evaporate away rather than be trapped in the wall. Limewash has a matt finish and helps consolidate and improve the surface of both old and new plaster both physically and visually. 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. ACS Mould Wash Concentrate) 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.
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.
Limewashing onto masonry or 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, therefore the benefits of the limewash will be 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.
NB. Please note that even with casein added to limewash it is very unlikely to last very long at all if applied over a masonry paint and subject directly to rain.
Safety
Limewash is caustic. Always wear eye protection and protective gloves and clothing and follow the safety instructions on the labels.
Information are advice 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.