A potter’s work surface is an important part of their work. Having a strong durable surface to work on can make a huge difference in the type of work they create. For the studio, I recently built 2 six-foot concrete slab tables and one 5-foot table, half concrete and half plaster. Below I’ll detail some of the more important aspects of how these were constructed. There are a lot of benefits when using a concrete work surface in ceramics. Far superior to a canvas table top because it won’t hold in dust, it’s also a stronger, more stable base to wedge and throw. The concrete absorbs moisture out of the clay as you wedge, making it a more durable wedging surface.
I used tables that I already had to pour the concrete onto. This saved a lot of money on extra materials to construct the table base. The only addition I made to the tables was to support the legs with 2×4′s to strengthen the table. For a 6-foot table I was adding about 250lbs of concrete, so it’s important to brace those legs! In the pictures below I show step-by-step how the shorter 5-foot table was made using half concrete/half plaster. We use this as our main wedging table because it gives a nice option between the two materials.
I built the frame to pour into from 1×4′s. This creates the basin to pour the concrete or plaster in. I put a separator down the center to create two basins, one for plaster and one for concrete. For this table I left the perimeter boards attached so the excess length will be cut off later. The concrete was poured to a thickness of 2″. This is plenty thick for a tabletop and not too thin that it will easily crack.
Screw in a wire mesh to the floor of your mold form. This adds extra strength to your table and prevents cracking. Be sure the mesh is fastened below the top level line of the form, but allow space for the concrete to get underneath the mesh. Ideally you want the mesh to be suspended inside the concrete form, not sitting below it.
Pour the concrete. I mixed mine up in a 5 gallon bucket. This section of table is about 1 1/3 bag of concrete. The first 1/3 of the bag I mixed up relatively dry. Once poured in, I adjusted the wire mesh to make sure it was suspended a little above the first layer of mix. Run a 2×4 across the top to check and make sure the wire mesh isn’t sticking up past the mold. Nothing is worse than pouring the concrete and finding out later that there’s a piece of wire sticking out. The next bag was mixed a little wetter, but still stiff; too liquid of a mix will result in a weaker table and a less smooth surface. Troll over smooth and let it begin to set up. While you’re waiting, mix up your plaster for the second half of the table.
With the plaster poured it’s now a waiting game. To get a nice smooth finish on your concrete you need to wait until just the right time before you troll it over with a flat blade. As the concrete is setting up run over it with a float to make sure you settle out the larger stones in the concrete, this will help for the final smoothing. Once it’s set up to the point where it is stiff yet still a little malleable. (I poke it with my finger, if it goes in wait a bit longer, if it leaves a finger print you’re good to go, if it leaves no mark, it’s too late). When you get to the right consistency run your blade troll over it, smoothing it out. If it’s at the right maturity you’ll get a super smooth almost glossy (from the moisture) finish. This is what you’re looking for. Once smoothed over let it set another hour or so.
Your next challenge is to keep the concrete (and plaster) wet for as long as you can. Sponging water over it every 20 minutes or so. The longer you can keep it wet, the stronger and more durable of a table you’ll have. Even a few days after you pour it you’re going to want to keep it saturated. Putting a plastic sheet to cover it over night will help.
Above is a picture of two other tables I poured that were solid concrete. They are 6ft by 30in. The concrete is about 2in thick. These took 3 1/2 bags of 80lb concrete each. The concrete I used was a “quickcrete crack resistant mix.” It was a little bit pricier ($5 per 80lb bag) but well worth the few extra bucks. The crack resistant concrete has small microfibers that help hold the concrete together, a lot like putting fiberglass fibers in your clay. Actually it’s the exact same thing. The plaster I used was “Casting Plaster #1,” you could use Pottery Plaster #1 but the Casting Plaster is a much tougher plaster and won’t chip or scratch as easily.
All in all, I built the 3 tables for under $100 (not including the original price of the table bases), and we now have much better and safer work surfaces for the studio.