Biochar Gypsum Plaster

A while back I spoke with my friend Uncle Mud about plasters. Somehow gypsum plaster came up. I enjoy using natural materials and know that the environmental impact is much lower when I take a shovel out to harvest my own materials from the land. Sometimes, a project really just needs to get done. So I began to test myself to discover what my building values were at the time. The curious monkey with a limited timeline won out.

I went out and bought some gypsum plaster (joint compound). The ingredients are still pretty natural, however I'm sure the processing has a higher impact. My other best option for this project was biochar lime plaster.  

Because I buy the sand from a local quarry and mix the plaster myself this cuts down on impact for lime plaster manufacture, but also requires a lot more time on my part. I am still unsure what the differences in impact are for processing of the hydrated lime versus the gypsum plaster are, but I haven't yet marked on my calendar some time to look into this ;)

The short story is, I feel I'm cheating a bit, compromising, but I'm also thankful to save some time and curious about the finished product. 

Biochar gypsum plaster instead of biochar lime plaster

If you have never worked with lime plaster before, then you should know it requires a little babying. The gypsum plaster really does not require babying, it is very user-friendly. 

I took my biochar and ground it in the blender until it was very fine, then mixed it with the gypsum plaster. It was easy and quick. After troweling it on I went back over to play with the texture and check out the thickness. 

In my first attempt I tried my friend's suggestion to add temepra paint for a beautiful color.  I added 2 cups to a small bucket. The color turned out a baby blue when dry. I decided it looked a little too artificial for me and went back over with one more time with just the plaster mixed with biochar.  Of course I love the tint that biochar gives. When damp the plaster is bluish, and it is speckled with larger black pieces if not ground too uniformly. 

Biochar is said to reduce humidity.  From my experience so far it does make a big impact.  Our house is in-ground. We have had to be careful of mold during certain seasons. So far, the rooms with biochar plaster on the walls have not had a problem with mold this year, though on a particularly rainy week we did find some mold in rooms that have previously been much less humid.  Now I want to plaster every wall with biochar.  Biochar can block certain waves and frequencies, though, so I am being selective to not block my wifi signal. 

On tinting with tempra:

I have seen some beautiful plaster tinted with tempra. From what I have read, a richer color may be reached by starting with a coat of plaster, then watering the plaster down to a paint consistency and adding the paint to this. The color then is painted on over, almost fresco style. I have yet to try this, and may soon do this with natural pigments. 

This is two coats over cinderblock. The lighting is a little strange in this picture, but the color of the plaster is uniform. I went for a bit of a scratched rugged texture, because I like my walls to make me feel like I am in a cave. The picture does not show a lot of detail, perhaps I will add a better one later. 

Lime plaster is much more durable, but definitely something I would recommend learning hands-on from someone who knows what they are doing. If you live in a warm, humid climate however lime plater becomes much easier. I found with my lime plaster that it is very important to keep it moist for a period of time, and ensure it is kept warm, with limited temperature changes to make sure it does not crack.  With the gypsum plaster, however, very cold temperatures will still cause cracking. 

This pre-made joint compound is a no brainer. Adding the biochar gives great benefits to air quality and humidity regulation, as well as adding a bit of carbon sequestering you can feel good about a small step to help with climate change. 

I like this mix. It was easy and I personally like the look. The biochar helped reduce humidity in the bathroom. When I want to work quickly I will use it again.  Still, I prefer the stone-like quality of lime plaster when I have the energy and time. 

Next time I may try a top coat of painted-on natural pigments mixed with plaster.