Shikkui (Japanese plaster) and Diatomaceous earth: Natural alternatives to zero or low-VOC paint

Human bodies are very slow to evolve. It takes long, long time – thousands or tens of thousands of years – for them to adapt to the changes in the environment. Naturally, they don’t really know how to react to a variety of chemical compounds that have been invented and/or released in the environment over the past couple of centuries. As it turns out, we have been finding, ex-post, that many of them were actually toxic or harmful. Some caused serious pollutions. On the contrary, traditional natural materials are proven to be compatible with our body, as they have been through ultra-long term feasibility studies. Not only are they safe, they often exhibit better adaptability to the environment compared to synthetic materials that are strong but inflexible.

However, despite the risks, modern society has been favoring synthetic/chemical products because they were far more efficient than natural materials, which were often more expensive to produce, lacked needed specifications, or were too time/energy consuming to use. But that is going to change. Today, many traditional material manufacturers offer substantially more efficient, user-friendly products, in addition to improve aesthetic effects.

Natural alternatives to zero or low-VOC paint

Take a look at wall paint products. Many popular brands have been known to contain certain level of volatile organic compounds (VOCs), such as toluene, xylene, acetone, formaldehyde or benzene, which are released as harmful gas (paint fume) when the paint is applied on the walls. By painting your walls, you could potentially be exposing your family to multitudes of health risks, not only short-term symptoms such as irritation of the eyes, headaches but also long-term impacts on your nervous system. Although brands like Behr offers low or zero-VOC products today, it’s worthwhile to check out their natural counterparts, which are not really paint but finish.

There are two traditional Japanese natural materials: 漆喰 (shikkui) and 珪藻土 (keiso-do.) Both are made from 100% natural ingredients, hence zero-VOC and free from any toxic compounds. They exhibit relatively coarse, rustic texture/feel with earthy colors: you can enjoy how natural light changes the expressions of artistically uneven surfaces in different times and seasons. As the unique surface finish is the key, plastering has traditionally been performed by experienced plasterers in Japan, who were called 左官 (sakan.) Although the number of sakan plasterers have decreased because of modernization and the economic environment that prioritizes cost efficiency over craftsmanship, there still are master sakan, whose work is art.

Works by Shuhei Hasado, one of the most prominent sakan (master plasterer) in Japan. (Note: he used clay in the video, rather than slaked lime (shikkui).

漆喰 (Shikkui)

漆喰 (shikkui) is made of slaked lime (calcium hydroxide) of high calcium purity. Just like stucco/plaster used elsewhere in the world, lime is blended with water, aggregates/binders such as seaweed extracts, natural plant fiber and other natural ingredients to make shikkui. When it’s applied wet on the surface, it starts curing time. Because of the way it hardens, shikkui requires more skills to apply, but once it’s set, it provides aesthetically pleasing texture and starts absorbing CO2 very slowly – until it turns back to calcium carbonate after 100 years. This “breathing” by slaked lime has the ability to regulate humidity and keep indoor environment comfortable.

If you are also for environment and sustainability, you may inquire Tagawa Sangyo (introduced in the video above), a Japanese company that offers shikkui products that are C2C certified. C2C means “cradle to cradle,” which is the concept spearhead by renowned architect William McDonough and chemist Dr. Michael Braungart in order to promote product design that takes a holistic sustainable approach from material extraction to reuse/recycle/upcycle so that the products become not only harmless throughout manufacturing – use phase, but also can be the feedstock, not waste, when they reach their end of life. Their shikkui can also be used toward LEED (green building standard in the US) credits.

Whereas shikkui is typically applied using trowels by skilled plasterers, the line-up offered by Tagawa Sangyo includes some user-friendly airless and texture sprayers, or products that can be applied with rollers and spatulas. In terms of upcycling, they also offer products that contain up to 50% in weight of fine aggregate of made from reprocessed chicken eggshells (which contain 95-97% calcium carbonate crystals, which are stabilized by a protein matrix to produce characteristics close to marble) that come from a Japanese mayonnaise manufacturer.

Here is how shikkui is applied and looks like.

珪藻土(diatomaceous earth)

珪藻土 (keiso-do) uses diatomaceous earth as its main ingredients instead of lime, and blends aggregates and binders such as clay, sand or charcoals. Although the process is similar to shikkui (slaked lime), diatomaceous earth is different in that it doesn’t harden on its own. Keiso-do, therefore, relies on other additives to stabilize as wall finish. It may be easier to apply keiso-do compared to shikkui because of the differences in curing process. Keiso-do has more distinct coarse surface, and usually offers more color variations.  

In the US, you may contact Shikoku International Corp, the Shikoku Chemicals’ US subsidy based in Orange County, CA that offers keiso-do wall finishing under the SATORI brand. According to Shikoku Chemicals, diatomaceous earth can absorb about 90% of formaldehyde, reduce unpleasant smells by 50-99% in 24 hours and regulate humidity. Indeed, diatomaceous earth can either absorb or release moisture depending on the ambient humidity: it absorbs when it’s humid, and lets out when it’s dry.