I’ve decided to sign up for another week at Art Camp Claudia McGill. So we’ll see what we do there this week. Hard to say, because the counselor doesn’t tell me, the lone camper, what we will be doing until I arrive. Each day is a surprise.
Today’s session involved concrete. Or, to be more correct, mortar mix.
As background, after last week’s stone carving session, I couldn’t get concrete carving out of my mind. What pushed me into it, though, was the half-used bag of mortar mix we had on hand after doing some re-grouting of the bricks on our house.
Mortar mix is a pre-mixed version of concrete specially formulated for non-load-bearing purposes, usually to bond together or fill surfaces such as in brick walls. It behaves in the same manner as concrete as far as carving. Maybe even better, since it is very fine and contains no irregularities.
I decided to keep things simple. I would create small shapes in free-form concrete, let them set up, and carve them into a herd of stone-age-art animals. This way I didn’t need forms or molds, which I hadn’t stockpiled. Each animal would be small, so that if it went wrong from a technical standpoint, such as breaking in half or large parts falling off during carving – well, the whole project wouldn’t be a disaster. I felt it important to work this way because it’s been a long time since I did any concrete carving and I questioned my skills.
OK. I assembled my tools. We had stopped at the thrift shop on the weekend to buy some basics – serrated knives, a table knife, and some pointy spoons, spending about $4. (A grapefruit spoon is even better, with its toothed end, but hard to find). And what I had on hand – A rasp (an old one, as concrete is ruinous to a nice rasp). Latex gloves (concrete eats skin, leaving little sores that really hurt). A bucket of water. A trowel. Rags. A couple of cardboard boxes. A large mixing container, one that I have used in the past. I also brought the hose around to the work area.
I took all these things outside. I then put some mortar mix into the mixing container. I didn’t measure it, as all I was adding was water, and I would decide on the proportions by eye and feel. Mortar mix is very powdery and should not be breathed in. So I used a small plastic container to transfer it from the bag, rather than pouring. If I were doing a large project, I would wear a mask for this stage.
I then added water, slowly, from the bucket, and mixed it with the trowel. I wanted it to be quite stiff, so that it would hold a shape. I was satisfied when things looked like this:
I let it sit about 15 minutes, then I began shaping it into forms. The technique is to grab up a handful and pat it together, with some force. Concrete cannot be pressed as clay can – it needs to settle into itself. If I were putting concrete into a form, for example, I would then vigorously tap the sides of the form to get the concrete to settle and compress.
I created a crowd of shapes and set them in the cardboard to set up. Concrete does not “dry” – it “cures”. It’s a chemical bonding that continues through the life of the object – concrete just continues to harden. Forever.
I cleaned the mixing container with the hose and went away and left things for four hours. When I came back, I could mark the concrete with my fingernail, but the shape itself did not budge. Knowing when to start carving is a judgement call and takes practice. The shape has to hold up to pressure but also needs to be soft enough to work with. Additionally, time passes as carving goes on, and the shape gets harder, so that needs to be taken into account. I had a lot of animals to carve and I would need to work fast.
My first step was always to rasp or carve away the “skin” on the outside of the shape.
After that, I looked over each shape and tried to find an animal in it. I guess it took me about 2 or 2 1/2 hours of work to assemble a herd.
I used the knives, rasp, and spoons about equally. They each have their strengths. Knowing how the tools work is also something gained through practice. I worked tentatively at first but it came back to me and I worked more fluidly as time went on.
A fair amount of debris is created. After each animal I cleared my board by tossing the leftovers into a paper bag to be thrown out later.
Once I was done, I thoroughly washed each item in the bucket (I had also used the water here to wash my hands at intervals). It is essential to get every bit of concrete off the tools. It will set and cannot be removed later. I also rinsed all work surfaces with the hose and later came out and rinsed off my clothes and the rags I used before putting them in the washer. Under no circumstances can anything be washed in a sink inside – concrete will flow down the pipes and, as it can set underwater, will block them. So, if you do concrete, remember this fact, if you remember nothing else!
I then left the animals outside overnight. The next morning, I came out and rinsed them with the hose.
If I were making larger items, or ones prone to cracking, such as stepping-stones, I would wrap each item in a wet towel and cover it in plastic, so that it would go through the initial stages of curing very slowly. I’d leave them in this state for about a week. With these little animals, though, it’s not as likely they will have those problems, so I will just come out and rinse them several times a day for a couple of days. I also have them set in the shade – the sun is not good for curing concrete.
OK! Stone age animals made. I’ll take some better pictures in a week or so, when they are ready to join the world.