The Joy of Lime Plaster

For the next month, HempStone will be in Goshen, MA for exterior and interior lime plaster over hempcrete. Of all natural building materials, lime, specifically lime plaster, is the favorite for Catalyst.

Lime plaster is simple to make and straightforward to apply, yet requires a careful and attentive approach to preparing and maintaining for the first 3-10 days after being put on a wall. In exchange, lime plaster will last for decades/centuries as a robust, durable, clean and hygenic finish.

Lime plaster is a joy to teach novice builders, as anyone can learn, and the basics can be understood in the span of a day. As a heavy wet finish, it’s great for enhancing your core strength and building muscles. As a natural material, it’s fun and easy to be around, with a bit of forethought and preparation.

Lime is high on the pH scale, and is thus caustic, so it’s important to have a few protections for your body. Here’s the basics:

Eye, skin, and respiratory protection:

We recommend respirators when mixing dry ingredients, as lime dust mixed with moist air in your lungs turns to limestone. Once that happens, you are forever carrying that in your lungs, which is not good. Once the lime has been mixed with water thoroughly, this stops being an issue. Once the lime plaster cures, it becomes limestone, which is stable and inert. In fact, lime plaster is anti-microbial and anti-fungal, ad is a joy to experience. Cured lime plaster offers a healthy, pleasant, natural wall surface that endures.

Goggles for mixing and applying, especially when applying material overhead. Lime plaster in the eye is the most imminently dangerous concern, so proper eye protection keeps you safe and supports a joyful experience. Have an eye rinse station, and preferably, a hose with a solid psi water flow for rinsing your eyes if needed.

Chemical-resistant gloves, either mid-arm or elbow length, are essential tools for plastering. Best practice is to put a second pair of tight gloves on underneath, in case some plaster or wet lime slurry gets in the first set of gloves. Hands in gloves tend to sweat, so if you get wet plaster inside, you’ll likely not notice for hours. Meanwhile, the lime will slowly dissolve your skin. It’s nothing to worry about, so long as you respect the power of lime and are meticulous with your skin care and protection solution.

Skin protection in the form of long sleeves, pants, and closed shoes is also highly recommended - especially for beginners and professionals who will be working with it all day. If you do get some on your skin, a rinse in vinegar water will immediately neutralize the lime. If you choose to wear short sleeves, keep a bucket of vinegar water handy to dash on.

Catalyst always keeps an extra set of clothes on-hand just in case a mixed batch gets dumped out. Saturated cloth is a vector for lime burns on the skin. If your clothes feel wet to the touch and you’re working with lime plaster, chances are, the lime is causing irritation to your skin.

That’s it! Once you are set with Personal Protective Equipment (PPE), the fun can begin! Join us next week for an introduction to putting lime plaster on a wall. Until then, happy lime week!

Photo Credit: Alex Sparrow of UK Hempcrete