Limewash is a traditional paint which has been used for thousands of years. You can use it inside and out to finish the lime work on your home. Limewash can be used over your lime plaster or render, or on any brick or masonry pointed with lime mortar. It is a breathable paint so it lets water vapour out of the walls and it’s free of VOCs, which lots of other paints are chock full of. VOCs can be quite harmful, especially to younger or older people, so it’s best to avoid having too many floating around in the air.
What does limewash look like?
Limewash has a natural, matt finish and has a depth which lots of modern paints lack. Because limewash contains very small crystals, it even looks to glow in the sun because it reflects the light. When it’s wet, limewash gets darker. This is fun to watch in the rain, but also it can help you spot any leaks as the darker patches of limewash show up problem areas.
Limewash can either come in its natural white shade, or it can be coloured using a natural pigment. The pigment needs to be added to the mix before the paint is put on the walls, at a ratio of around 20:1 for most jobs.
How to make limewash
There are a couple of ways of making limewash. You can either mix up some hydraulic lime (this comes in powder form) with water to form your own putty to paint with, or you can use ready-set putty diluted 50:50 with water.
Which option is best?
What you’ll need to consider is the cost as well as the safety of both methods.
Mixing powdered hydraulic lime with water sets off a chemical reaction which produces heat. Using this method, you need to be very careful not to touch the mixture or let it splash onto your skin and you must use a container which will not melt or be otherwise damaged by the heat. This option is the cheaper of the two at roughly £12 per 25kg bag, but is a little more difficult to perfect and can be dangerous.
Diluting ready-made lime putty with water avoids any chemical reactions as these have already taken place. You will still want to avoid any contact between your skin and the caustic limewash, but there won’t be any need to worry about heat burns. This option is slightly more expensive at roughly £10 per 20kg tub, but is the easier of the two.
How much do I need?
Limewash is very economical, and will cover a lot of wall for your money. With 20 litres you should manage to paint 60-80sqm per coat depending on the wall type.
Painting with limewash
Painting with limewash takes some care. Limewash is caustic, so to avoid any burns or irritations make sure you’re well-covered with gloves and a pair of goggles as well as clothes you don’t mind splashing. If you do get any paint on your skin, wash it off quickly.
Use a good paintbrush to apply the limewash, as using a paint roller can create a rough, uneven surface.
Paint with limewash when the weather isn’t too dry or too wet. Too dry will mean getting dust in your mix, and too wet is no good either. However, you do want a little dampness on the wall before painting so use a hand-spray to spritz the wall as you go.
For limewash to stick, it relies on suction between itself and the wall’s surface. It copes very well with natural materials like lime renders and plasters, stone, or brick, but it won’t work so well with modern materials and finishes.
You might have to give limewash a hand with binding in very exposed places. Use additives such as casein, tallow, or linseed oil if needs be, but bear in mind that this will lower the breathability of the paint a little.