Sealers for Plaster, Tadelakt and Lime Wash:

Lime-based mineral finishes are amazing for their anti-microbial, anti-static, hygroscopic and humidity controlling characteristics; not to mention their inherent beauty and the movement that these finishes create in a space. So what's their weakness, it all sounds too good to be true, doesn't it. Well nothing is perfect even if we are celebrating the hand-made nature of these finishes they still have one draw back. They can stain. Uhhh! There I said it, these finishes are naturally porous, it's part of what gives them their depth and beauty. However this also leads them to being suseptible to staining or showing wear marks. So what are we to do? What are the options?

Well there are two basic options, leave them as they are and let them patina naturally based on the type of wear they are going to see, or put a sealer over them to make them some version of more wipable, stain-resistant and less likely to patina. Let's go over the do nothing option first before we dive into the different types of sealers.

Leaving lime based mineral finishes to patina naturally is a perfectly acceptable and even desireable route to take when living with these finishes. Why leave them unsealed? All of the awesome properties that lime finishes possess are diminished or completely absolved when we put a sealer over them. Depending on the sealer used, there may be mild affects or even a complete dissappearance of the finishes previous benefit, e.g. using an acrylic sealer will completely remove the limes ability to absorb and release humidity, negate its anti static nature and it's no longer an anti-micorbial surface. Leaving lime-based surfaces unsealed will leave them open to staining from, your body oils, (think of a surface you always touch like near a light switch) pet wear, especially rubbing around corners, water spotting etc. Even Tadelakt, the most water, stain, oil, resistant lime finish is susecptible to staining, especially from shampoo bottles setting on it.

When making the decision to seal or not seal, the things to consider are:

1. Are you okay with patina. Are you okay with a surface that slowly changes over time showing use?

2. How hard is your family going to be on the surfaces? Is this an adults bedroom? or is

this the mud room where you wash the dog?

3. How important are the natural attributes of lime to you? Are looking forward to less

scrubbing of showers walls because its anti-microbial? Do you live somewhere dry and

dusty and are looking forward to the anti-static nature of the walls? Maybe you have

allergies and are looking forward to taking advantage of walls that don't support

microbial growth.

A lime washed wall with no sealer in a residential bedroom.

Not sealing lime plasters and lime wash lets you take advantage of limes amazing properties, but you have to be open to the idea of patina, or living with that one-off -accidental-stain. If that doesn't sound like you or your expectations, let's talk about sealer options.

Acrylic Sealers: Think of acrylic sealers as applying a clear coat of paint over lime washed or plaster walls. The advantages are many. Your walls will perform more like what you are traditionally used to. Most food stains are easily wiped up. Dirt and body oil wipe away easily as well leaving your wall looking closer to what it looked like the day it was finished. Acrylic sealers also give you the option to add color depth or not, sheen or not. You can get matte sealers that have a minimal impact on color. You can get "wet look" sealers that are shiner and make the color darker, similar to the wet look of a concrete sidewalk after it rains.

Unfortunately the draw backs of using acrylic sealers are many as well. Acrylic is essentially a sheet of plastic over the entire surface. It will hold a static charge, and thus dust and pollen will stick to it. It can harbor mold, and it deminishes or completely takes away all the wonderful natural traits of the lime finish.  They are not breathable. Many acrylics have an inherent toxicity in and of themselves, though there is a wide range out there, and there are situations to use them. This is the sealer to use for that aforementioned mud room where you wash your Saint Bernard.

"Mineral Sealer": Penetrating sealers come with many different formulas, they may be acrylic based, silicon based or even oil-based but they all behave in a similar way. These sealers soak into the plaster or limewash finish and fill the porous surface with usually some type of hydrophobic substance. It may be a saponified oil, it may be a drying oil, it may be a plastic, but essentially these sealers sit in the pores of the surface and prevent stain causing compounds from getting into the surface. They are usually wipeable, water repellant, but suseptible to oils or grease. The nice thing about this type of sealer is they tend to leave the look and feel of the plaster mostly intact with minimal change. (though on darker colors it can have more of an impact) Penetrating sealers are great for areas of the home that are higher traffic, or someplace like a kids room where you expect you may need to wipe the walls occasionally.

Wax Sealer: Wax is a great sealer for plaster or lime wash walls because its creates such depth and lustre, it is hard not to fall even harder for your walls. Wax provides great protection against all types of liquids and oils. Wax is also anti-static, though it is considerably less breathable and can support microbes. The three biggest things to consider when you wax a wall however are: one the sheen (do you want shiny walls), two a waxed wall will eventually show wear and need to be spot waxed or maintained. Finally, once you wax a wall that is it, there is no changing it without sanding the wax off first. I have not met a primer yet that can stick to wax.

Soap as Sealer: Lastly there is the soap option. Soap? You say. Yes soap. When we employ the Tadelakt technique while plastering the final step is soaping the wall while the lime plaster is still actively curing. This creates a naturally hydrophobic layer. Well that same soap can be applied to dry plaster or lime wash and creates a beautiful sealer that is something like a cross between a penetrating sealer and wax. The soap sits in the pores of the wall occupying space that could be occupied by dirt or oil. It can also build slightly on the surface giving a low luster sheen and added depth. If you ever have to really scrubb a wall with water and soap, you will have to re-apply soap sealer but it tends to blend well. You can also have fewer coats applied to control how much the sealer "shows" on the surface, its very customizable to achieve not only function but aesthetic as well.

A soap sealer adds depth, sheen and protection to this powder room lime washed wall.

These are the most common sealers I use on walls. They all have their place, I think, and I take the time to discuss and recommend what I think will be suit a clients needs and expectations. That said, I do love the look of an aged plaster wall, patina and all.