Season 1: Project #20 Pot and bothered - Anything I Can Do

Hypertufa is a mixture of cement, peat moss, and sand designed to imitate volcanic stone which was once used in England as watering troughs for livestock. The troughs were later used as planters by English gardeners, but eventually the supply ran out.

Hypertufa was invented as a substitute material for planters and can be shaped in almost any way. It has the appearance of stone, but is also lightweight enough to be moved around the patio. Once cured, it's freeze- and thaw-proof so it can be left outside year-round.

With hypertufa, you can build pots, benches, birdbaths, stepping stones, troughs, planters, fountains, faux rocks, garden sculptures and even (if you don't trust the aesthetic judgment of your loved ones) your own tombstone monument.

You can either work free-hand (for sculptures or faux rocks) or work with a mold that is similar to the shape and size of the pot you want to make. The hypertufa material can be packed onto the inside or the outside of a mold. Packing it on the outside of the mold gives you a more rustic, natural stone look, while packing on the inside of a mold will give you a smooth outer surface.

Open the bags containing the ingredients being careful not to raise dust from the Portland cement bag. Portland cement is very caustic because of its high alkalinity, and can dry and burn your hands eyes and lung tissue. Therefore, be careful not to raise cement dust.

If you can't restrain yourself, wear a dust mask. Always wear gloves and eye protection. Should you get some on your skin, rinse it off with water and vinegar to neutralize the alkalinity of the lime in the cement .

Basic mixtures:
The Classic - 1 part Portland cement, 1 part sand, 2 parts peat moss
The Smoothie - 1 part Portland cement, 1.5 parts sand, 1.5 parts peat moss
The Lightweight - 1 part Portland cement, 1 part peat moss, 1 part perlite, 1 part fibermesh (little pieces of fiberglass to add strength)
The Sparkly - 1 part Portland cement, 1 part peat moss, 1 part vermiculite

Optional additives:
Acrylic fortifying admixture (used to strengthen and add flexibility to concrete products)
Concrete or grout dyes and pigments to add colour
Earth pigments
Iron fertilizer (makes the hypertufa go a rust colour).

Use a container to measure the ingredients into the wheelbarrow. Put the cement on the bottom (to control dust) and the other ingredients over it. Add some water and mix with a hoe or shovel. Continue adding water until the mixture is a good mudpie consistency. It should stick together without being so gooey as to slump or so dry as to crack.

It is easy to add too much water too fast. Mix the water in thoroughly and let it sit for ten minutes and mix again. The peat moss tends to absorb more water over time and if it is a hot day the mixture will dry out. It is easier to add water to a dry mixture than adding more dry ingredients to an overly wet mixture.

NOTE: If you're using a recipe that's loaded with peat, remember that the peat is very absorbent. It leaches water from the mixture, drying it out horribly! Then your pot falls apart and so does your composure.

Cover the mold you've chosen with thin plastic. The mixture won't adhere to the plastic so it will release easily from the mold. Tuck in the folds of the plastic sheeting so that it doesn't get embedded in the hypertufa.

Start patting the hypertufa mixture on to the bottom and work up. The thickness depends on the size and style of the pot you intend to make. It should be at least 3/4" thick for a very small pot and roughly 2" thick for a large pot. Make a solid bond where the sides of the pot join the bottom, and don't skimp on thickness. Pack the material well in this area so that the pot doesn't crack along the outside edge.

Flatten the bottom while it is still wet using a trowel or piece of lumber. Then make a drainage hole with a stick or pencil.

Leave it 24 hours to set.

After 24 hours, carefully pull the pot away from the mold. The pot will still be very fragile because it takes about 20 - 40 days for the cement to cure completely. At this point the material is still soft enough to shape the bottom of the pot and make it more stable if necessary. Use a trowel to scrape off some of the hypertufa until the pot is stable while sitting. Wire brushing the surface (especially where the hypertufa was pressed against the plastic sheeting) will give your piece a roughened weathered appearance.

Let the pot cure for a further four to six weeks.

Once it's fully cured, rinse the pot with lots of white vinegar to remove the alkalinity, thus preventing damage to tender plant roots.

Fun finishing touches:
Paint the finished pot with beer to encourage lichen and mold to grow, adding surface texture and apparent age.
Plant moss in any cracks and crevices on the outside of the pot; its roots will take hold in the peat.
Put moss together with yogurt (or buttermilk) in a blender and whirl it around. Paint the resulting mixture on the outside of the pot to start moss growing all over it.

Gerri Binks

Sean Casey