Earth Based Finishes for Walls

Kurt demos proper hawk and trowel technique.

I just spent a blissful weekend in the California desert learning earth based finish techniques from adobe master Kurt Gardella. Some observations:

  • Earth plastering is not something you can learn from a book. It takes practice and hands-on experience. In this excellent workshop we got three full days of learning the techniques both for indoor and outdoor surfaces.
Clay, sand, wheat paste and prickly pear juice as an exterior plaster.
  • There’s no simple recipe for earth based finishes since clay and sand have different properties depending on where they come from. You figure out the right proportions of clay/sand/straw by doing test patches. Too much clay and the surface will crack. Too much sand and it wont stick to the wall when you try to trowel it on. Straw can be used to strike a balance. We did a second scratch coat on the first day that ended up cracking badly. We tried to add more sand but that made the plaster too hard to trowel on. The solution was to add more straw, which allowed us to keep a higher clay content in the mix, while preventing the coat from cracking when it dried.
Kurt shows how to work over the final mud plaster coat.
  • Earth based walls have an indescribable, almost metaphysical presence. I had been in the small desert cabin we plastered when it had wood paneling. Once the walls were filled with cob and the plaster coats applied it had a weightiness that’s difficult to describe in words. Some other advantages: it absorbs sound, regulates humidity and is a good insulator. Drywall seems flimsy in comparison. There’s something about traditional plastering techniques (even the lath and plaster of our 1920s house) that give a room a comforting feeling. Of course, plastering with a hawk, trowel and darby take a lot of skill and time which is why they are seldom done anymore. It’s a pity.
Image from japanesetrowels.com
  • The Japanese make the best trowels. And, yes, there is a japanesetrowels.com. The flexible ones are especially nice for finish coats. But they ain’t cheap.
Fermenting prickly pear.
  • Rotted prickly pear cactus juice, combined with some wheat paste, makes an amazing stabilizer when mixed with adobe. The mucilaginous texture of prickly pear gives adobe a stability that helps it resist water penetration. To extract the cactus juice you chop up prickly pear, put it in a bucket with some water, and let it ferment for a few weeks. We used a prickly pear stabilizer in a mix that covered the top of a cob oven.

If you’re interested in learning adobe techniques Kurt Gardella will be coming to LA to teach a class on oven building. More info here. Some plastering will be done in the course of the oven class.  There’s also a nice book on the subject: Using Natural Finishes: A Step-by-Step Guide.

One last thought: Working earth plaster by day and sleeping in a cozy desert cabin with a copy of the Odyssey is just about as perfect a life as I could hope for. Thank you Meredith and Doug for your hospitality!

Insect Hotel

This is old news, but we thought it worth repeating in light of last week’s review of Attracting Native Pollinators.

Above is a picture of the winning design of a native pollinator habitat built by Arup Associates in response to the Beyond the Hive competition put on by the City of London.  The Core77 post we’re linking to has more views and also some pics of the runners up. It might give you some ideas for building your own habitats at home.

How to Make a Mosaic Stepping Stone

Not liking the pre-fab stepping stone options out there, I decided to take matters into my own hands and make one with glass mosaic tile. It’s easy to do using what’s called the “indirect method” in which you press the tiles onto a piece of contact paper. You then use that sheet of tile to cast your new, custom stepping stone.

The first step is to come up with a design, either hand drawn or printed out from the computer. Since you’ll be working in reverse, you flip your design left-right. I chose the mercury, the symbol of transformation (it seemed like a good metaphor for a garden). No need to flip this particular image, of course. When sizing the design I like to keep in mind the size of the tiles I’ll be using so that any lines are about one tile wide.

I transferred the design to a piece of clear contact paper. Next, I taped the contact paper, with the sticky side up. to a piece of melamine coated fiberboard. Melamine is a good material to use because it helps it has a very smooth, even surface and is unlikely to warp. In addition, using melamine for the sides of the mold helps it release more easily. I built this mold out a piece of a discarded Ikea bookshelf.

While I was cutting the bottom piece, I cut four additional small pieces of the bookshelf to form the sides of the mold.The dimensions of these pieces determine the size of your stepping stone. I made a simple box by joining the pieces with screws at the corners. If you wish, you can spray the sides of the mold with WD-40 to help release the mold later. I forgot to do this, but it released fine anyway

For the mosaic itself, I used glass mosaic tile leftover from an old project. The glass picks up reflections and shimmers on a sunny day. The drawback is that it’s pretty expensive. The brand we’ve used in the past is Bisazza. You can also, of course, use broken plates, pebbles, pieces of metal or tile left over from other jobs.

To cut glass tile I use a pair of tile nippers. I like to break the square tiles into four small pieces to simulate the irregular look of ancient mosaics. I wear a pair of safety glasses and do the cutting in a box to keep shards of glass from flying around. I also do this outside or in the garage so little shards of glass don’t end up in our house. Once cut, I press the little tile pieces against the sticky side of the contact paper–face down, or “good side” down.  The sticky paper holds them in place.

When you’re finished sticking all the tiles down, it’s time to mix up some concrete. I used one part Portland cement to three parts builder’s sand. I poured my concrete into the mold and used some chicken wire as reinforcement. I just cut the wire into a rough square that would fit in the mold, poured half the concrete, placed the wire in the mold, then finished the pour. 

Once cast, I put the stepping stone in a garbage bag to slow down the curing process. After a couple of days I carefully removed the mold. One advantage of this technique is that it’s “self-grouting”: the concrete should flow between the tiles during the pour. It worked well, but I will have to do a small amount of grouting to fix a few spots the concrete did not reach.  

You could also use this same reverse method to make designs that could be pressed into a mortar bed when tiling, say, a kitchen or bathroom.

For more garden mosaic ideas see a previous post we did on the subject that includes a link to the stunning pebble mosaic work of Jeffery Bale.

Easy To Make Furniture: Sunset DIY Manual From the 1970s

PVC pipe and an avocado colored cushion? Instant outdoor furniture, or so this campy 1970s furniture manual, Easy-to-Make Furniture,from the editors of Sunset Magazine, would have you believe.

While I think DIY furniture books from this period are somewhat horrifying, I have a respect for their can-do attitude in the face of the era’s declining wood shop skills. Then, WHAM, the global economy and Ikea came along and wiped out the last remaining economic reasons to try to make your own furniture.

That being said, I think some clever folks with time on their hands and an eye for discarded materials could make use of some of the concepts in this book.

So start dumpster diving! Let’s take those scavenged materials and revisit the bean bag. Easy-to-Make furniture has its own unique twist on the concept. Say hello to the “Multiposition Tube Seat”:


And yes you can have a particle board chair:

With a built-in magazine rack:

Scope out this book in its entirety here.