Limewashing is an ancient tradition - it’s one of the oldest paints known to man, used in ancient Egypt and Rome thousands of years ago, but also still used to this day. Throughout history, limewashing was a cheap and effective way of painting houses. It’s breathable and long-lasting, and also possesses some antibacterial insecticidal properties.
Limewash was also used so frequently because of its fireproofing properties - after the Great Fire of London in 1212, King John decreed that all houses on the Thames must be covered with lime paint. It was also thought to make stone buildings stronger, filling cracks in rocks and weatherproofing the structure.
Nowadays, limewash is mostly used to paint exteriors, often with a dye added to give it a tint of colour. While its use is uncommon in modern times, it’s making a slight comeback due to its vintage, rustic vibe.
If you’re planning on using limewash in your project, you need to know how to properly make use of it - here’s a short guide on safe application of limewash that should help you out:
Why even use limewash?
While you might think that people nowadays only use limewash for its hipster flair, there’s a little more to it. Some types of wall constructions are built in a way that keeps a certain level of moisture inside of it. If that moisture doesn’t find a way to escape, it might cause decay in the future.
To get rid of that moisture, we must rely on the surface material, such as paint, to be permeable. Some types of modern paint and most available mortars are not permeable, which could lead to structural damage in some walls after a time. To avoid that, a lot of people use limewash.
Limewash is one of the most permeable materials available for finishing walls - tested through thousands of years by people from all over the world. It’s useful and looks great - why not use it?
Why is it difficult working with limewash?
As you can imagine, limewash isn’t an all-around solution to exterior painting - as you can see by how infrequently it’s actually used nowadays. Without additives, limewash is very simple and easy to make - it’s only slaked lime (calcium hydroxide) and water. After applying the mixture, limewash combines with the carbon dioxide in air to form calcium carbonate through a process known as carbonation.
Unfortunately, carbonation is an excruciatingly long process. As the limewash can’t dry too quickly, it’s required to apply one coat per day until the end. What’s more, weather conditions need to be almost perfect for your whitewashing to be successful - strong wind, strong direct sunlight and heavy rain could destroy the whole process.
Thankfully, there are ways to safely and effectively work with limewash in modern times.