Most home interiors these days are constructed with commercially made drywall. The days when plastering was a dignified occupation of skilled workers who passed down their art from master to apprentice have long since passed. Drywall, aside from being rather simple and unattractive, can also be filled with enormous amounts of dangerous chemicals. Natural plasters are a way to create a beautiful home interior that won’t leach chemicals into the air you breathe.
The Lost Art of Plastering
Before the days of 2×4 and plywood timber framing construction, homes might have been built out of adobe, brick, or even stone. While these materials can make beautiful exteriors, they aren’t the ideal interior for a bedroom or kitchen. Plastering was what helped embellish a home interior by covering up the inside walls with a smooth textured material that helped to create warmth, color, and attractiveness to the room.
Different plastering techniques have been used over the course of history. The natural materials that were used for plastering a wall were usually locally sourced and depended on what was locally available. In certain countries of Central Africa, for example, log and palm frond homes have traditionally been plastered by mixing together local clay with fresh cow dung known as litema. The enzymes in fresh cow dung react with the minerals in local clay to help harden the mixture and prevent cracking.
In the northern Sahara Desert, cows and clay are hard to come by. In Morocco, local plasterers came up with “tadelakt”, an ancient plastering technique that uses lime and some sort of sandy aggregate. Since sand was in plentiful abundance and lime quarries could be found, this traditional plaster option created beautiful, rock-hard, and waterproof plasters from all local materials.
The Dangers of Drywall and Commercial Paints
Unfortunately, our modern day world is more focused on efficiency and cost-effectiveness that quality and beauty. Natural plasters such as litema and tadelakt have been replaced by commercially made drywall and latex paints that can be put up and painted in half a day.
Most drywall today is made from gypsum which is encased by paper or cardboard. While gypsum is a natural material, there have been several documented cases of drywall that has contained aggregate material that is known to be carcinogenic. Recently, large amounts of Chinese-made drywall was recalled from North American markets because it was discovered that it contained phosphogypsum, uranium, and radium, all of which are known carcinogens.
Furthermore, most commercial latex-based paints have been shown to contain volatile organic compounds, or VOCs. These VOCs are breathed into our bodies while the paint is wet on the walls and are believed to contain several substances that are harmful to the human body, potentially causing cancer, liver damage, asthma, and other negative health effects. Even after the paint dries and the smell of fresh paint has disappeared, these VOCs can continue to leech off the wall and into the air in your home creating a long-term health hazard for you and your family.
How to Make an Earthen Plaster
One of the main attractions and benefits of natural plasters is that they lend themselves to creativity. Whereas drywall comes in straight boards, natural plasters can be applied to curved walls, can be made into relief sculptures, or can be utilized in any artistic practice you can think of. While there are a number of different natural plaster techniques, most natural plasters are divided into two categories: lime based natural plasters and earthen natural plasters.
Earthen plasters use earth or dirt as the main ingredient. Depending on the percentage of clay in your soil, you may also have to add sand to your mix in order to prevent cracking. For most all earthen based plasters, you want to shoot for 80% sandy soil and 20% clay soil. To find these proportions, an easy technique is to place your soil (or your soil mix with clay and sand) into a clear mason jar. Add water and shake the jar until it is one muddy and cloudy mix.
As the mixture settles, the grains of sand, which are heavier, will settle first, and then the clay will settle on top of the sand. After an hour or two, you should be able to see clearly defined lines where the sand ends and the clay begins. This simple process of separating the sand and clay present in soil will help you determine whether you need to add more sand or more clay to your mix.
To make your earthen plaster you will need to sift all of your ingredients through a fine screen such as a window screen. You can either let the soil you are going to use dry out and crush it into a powder, or mix it with a paint mixer until it is the consistency of a runny milkshake and then pass it through the screen in its wet form.
If you are going to be mixing sand and clay, you can sift these ingredients apart before mixing them together either in a wheelbarrow or on top of a tarp. Once your sand and clay are well mixed together, you need to add some sort of fine fiber material. This could be cattail fluff or finely sifted horse manure. The small fibers help to hold the plaster together and prevent cracking.
Finally, you need to add a glue. One of the easiest “glues” that you can add to an earthen plaster is a wheat paste that you can make by boiling water and simple, white flour until it is the consistency of a runny milkshake. Add this glue mixture to your plaster mix until it is wet enough to be workable (again, you are shooting for a milkshake consistency).
To apply an earthen plaster to a wall, you will have to wet the wall enough to make sure that the earthen plaster can stick to the substrate below it. You may have to do several coats of plaster, each one with finer materials until you get the look that you like.
How to Make a Lime Plaster
Lime plasters are somewhat easier to make than earthen plasters. Since almost every hardware store or agricultural supply store sells bags of hydrated lime, all you will need to do is add water to the lime dust and mix it up in order to make a lime putty. This can be done in five gallon plastic buckets. The longer you let the putty sit, the stronger it will become.
To make your lime plaster, simply finely sift the sand and mix it in a one to one proportion with the lime putty. You may need to add some water to make it the same consistency as an earthen plaster.
Lime plasters can be applied to any wall substrate that has been previously wetted. One of the interesting aspects of lime plasters is that as they dry with exposure to the surrounding air, the lime will reabsorb carbon dioxide from the air to harden back into a form of limestone. This makes lime plasters carbon neutral and also assures that your walls will effectively be caked in limestone.
Natural Plasters for a Healthier and More Beautiful Life
Natural plasters, whether they be earthen or lime based plasters, are a fantastic option to do away with the carcinogenic materials coating the walls in your home. With the earth beneath your feet and a few bags of lime, you can create beautiful interior and exterior plasters that will beautify your home and leave you and your family breathing pure, uncontaminated air.