Lime-Based Paint: Add Color to your Home While Capturing Excess CO2

Thanks to its CO2-absorbing properties, lime-based paint might be the healthiest and most ecological paint option for your home. We've written in the past about how lime mortar and related products have been shown to result in negative-zero (-2%) carbon emissions, making them an excellent alternative to portland cement.

In this article, we'll discuss how to use lime paint, the pros and cons, and what makes it so healthy and sustainable.

For thousands of years, people worldwide have been using lime wash to paint the exteriors and interiors of their homes. Lime wash is slaked lime (usually in powdered form) combined with water to make a simple paint. Through a natural process, the lime is able to re-absorb carbon dioxide from the surrounding air during its carbonation process.

A lime wash can be used as the final coat of a wall or on heavily porous surfaces where you want the lime wash to absorb into the substrate. Unfortunately, lime wash is not very durable and will wash away with time. Because it tends to erode due to exposure to the elements, a simple lime wash will require a renewal coating every five to seven years. Furthermore, it is also important to only apply lime wash on overcast days to keep it from drying too quickly, which could cause cracking. When fully dry, lime wash may also rub off on your clothing.

On the other hand, lime-based paint offers the same environmental benefits as lime wash but with added durability. Lime paint is a full-bodied paint that is highly versatile. Unlike lime wash, lime-based paint has a higher viscosity or thickness of the paint. This is achieved by using authentic slaked lime, which is obtained by the action of water on lime, usually by soaking the lime in water for years on end. Other companies add other elements to the slaked lime to improve the viscosity and durability of the lime-based paint.

Graphenstone is one such company that has improved traditional lime paint by adding graphene fibers, which optimize its properties and give it durability. Graphene is made up of a hexagonal lattice of carbon atoms that is just one atom thick, which provides the paint with its extreme durability.

Lime-based paints tend to be completely free from VOCs, carcinogens, and toxic substances, especially if they use mineral pigments for the color. As we mentioned above, when the lime is carbonating, it absorbs CO2 from the ambient air and cleans the air that you breathe. Lime-based paint, then, is a great alternative for people who want a healthy and environmentally friendly paint that purifies the air while also extracting excess CO2 from the atmosphere.

Hydrated lime, or the quick lime used for construction purposes, is formed by burning sources of calcium carbonate (CaCO3), also known as limestone (or occasionally magnesian limestone). The burning process requires high temperatures between 850°C and 1200°C, which forces carbon dioxide out of the limestone (and into the atmosphere) to create calcium oxide (CaO, or quicklime). The calcium oxide is then slaked with water to produce calcium hydroxide eventually (Ca(OH)2) used for construction. While lime also requires burning in ovens at high temperatures, lime requires less energy to produce than cement due to lower temperature requirements.

While building lime does release carbon dioxide into the air during the burning process, lime products can absorb the carbon dioxide in the atmosphere through a process known as the lime cycle. The lime cycle begins when limestone is burned and releases CO2 into the atmosphere. The slaking process eventually creates calcium di-hydroxide, sold as a bagged lime powder. This can be mixed with sand or other coarse aggregate and water and used as a more natural mortar (and plaster) alternative. As the mortar hardens, it reabsorbs the carbon dioxide in the atmosphere and eventually re-hardens into limestone. Through this cycle, lime is widely considered a carbon-neutral building material, as it reabsorbs the carbon dioxide released during manufacturing.

According to Graphenstone, three 15-liter buckets of their lime-based paint can absorb more than 14.7 kg of CO2. Thus, one square meter of Graphenstone paint equals one tree's carbon sequestering capabilities.

Lime-based paint can be applied to both exterior and interior walls. Like any paint, lime-based paints can come in dozens of colors. Graphenstone paints currently offer over 1,000 colors to choose from. With other lime-based paints on the market, you might be able to find products that come in different thicknesses. Because lime paint is full-bodied with a full viscosity, it can even be troweled onto the wall for thicker applications. You can also choose to dilute the lime-based paint to the level of wash you desire. Given the thickness you decide on, you can then choose to either roll, brush, or spray the paint onto your wall surface.

The paint will gradually erode with a basic lime wash, especially with exterior applications and when exposed to the elements. Though this slow erosion can produce a gorgeous weathered look, homeowners wanting to maintain the original opaque coverage will need to reapply the lime wash every five to seven years.

Lime-based paints offer a simple and straightforward way to create a gorgeous look for your home without the noxious VOC fumes and other toxic chemicals that have been lurking inside our paint products for too long. As an added benefit, lime-based paints will also help you reduce your carbon footprint by capturing excess CO2 from the atmosphere.

Article by:

Tobias Roberts

Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.