Since it is summertime, I thought I would share this great summer project from the latest issue of Pottery Making Illustrated! In this project, Sumi von Dassow demonstrates how to make an olla watering system out of clay. What’s an olla watering system, you wonder? It is an unglazed porous bottle form that is buried in the garden amongst your plants. When it is filled with water, it slowly releases the water into the soil to be drawn up by your plants roots when they need it. Read on to find out how to make your very own! – Jennifer Poellot Harnetty, editor.
As pottery and cooking go hand-in-hand, so too do cooking and gardening. Potters know the pleasure of cooking and serving from hand-made dishes designed especially for homemade recipes; and every cook knows the sweetest peas and corn are those that are harvested fresh from the garden moments before they are to be eaten. To complete the triangle and bring pottery into the garden, you can make ollas to keep your thirstiest vegetable plants healthy and productive through the hottest summer weather.
An olla (pronounced oya) is an unglazed bottle made from porous clay. Filled with water and buried next to a garden plant, the olla allows water to seep slowly into the soil to be drawn up by the roots as needed. Tomatoes growing with an olla suffer less from cultural problems such as blossom-end-rot as they receive a steady supply of water. Cucumbers are less likely to grow bitter in hot weather. Pumpkins and squash can grow big and plump without splitting their skins. Ollas keep the soil from drying out but never contribute to overwatering—if the soil is moist enough, water doesn’t seep out of the porous clay. As long as you keep the olla full, the plants always have exactly as much water as they want.
For most purposes, a fairly large olla is desirable so you don’t have to fill it too often. You want a nice round bottle with a long, narrow neck so you can bury it fairly deep and leave the neck sticking out of the ground for easy filling. You can throw a bottle from 6 or so pounds of clay, trimming the excess from the foot as needed. Or, you can make a bigger bottle with less clay if you throw it in two sections.
Start with 3 or 4 pounds of clay and throw a sturdy bowl on a bat. This will be the bottom section of the bottle, so don’t make it too delicate. When you cut the rim, bevel it so it angles down toward the inside of the bowl, then measure the outside of the rim with calipers (1).
With an equal amount of clay, throw a second bowl (this will be the top section), but open it all the way down to the bat, making an opening big enough to get a few fingers inside and leaving a generous amount of clay at the base. Measure the rim with calipers to make sure it matches the rim diameter of the first bowl, and bevel it in the opposite direction. This means it needs to angle down toward the outside of the rim. With the two cuts angled in opposite directions, they will fit together perfectly and make a more secure joint than two flat cuts. Don’t wire under either piece.
Allow the base bowl to stiffen slightly, so it can support the weight of the second section. Put the bat with the bottom bowl back on the wheel and pick up the bat with the second section. Flip it upside down, holding it by the bat so it stays perfectly round, and set it on the first section rim to rim, matching them up exactly (2). Use your fingers and then a stiff rib to smooth the two pieces together. Cut the top section free from the bat by running your needle tool under the edge as far as it will go, then cut it the rest of the way with a wire. Remove the bat.
There will be a thick collar of clay where the pot was stuck to the bat. Use this clay to form a tall, narrow neck. First you need to make the opening large enough to get your hand inside to smooth the area where you joined the two sections (3). Next, pull up the neck and collar it in until it’s about three inches tall and the opening is 1½ inches or so in diameter (4).
You shouldn’t have a lot of clay to trim from around the foot, but if you feel it’s heavier than it needs to be, trim it with a trimming knife (5) or turn it over in a chuck to trim. You don’t need a foot on the bottom—in fact the bottom doesn’t even need to be flat—but you shouldn’t leave it too heavy. Water will pass through it more quickly if it’s not too thick. Bisque fire the pot.
Ollas are forms commonly made by the famous Mata Ortiz potters in Mexico. See this Mata Ortiz pottery project in the PMI archives!