Using hypertufa is an inexpensive way to create practical garden art. Hypertufa is a type of artificial stone first used in the mid 19th century to replicate tufa, natural volcanic rock that forms from evaporated lime-rich water, leaving calcite to crystalize alongside iron oxide impurities (rust).

Hypertufa is a mixture of sand, peat, various volcanic aggregates and cement that is lightweight compared to stone or concrete and freeze-proof if properly cured. The basic recipe ingredients are varying combinations of Portland cement, peat moss, sand (sometimes perlite or vermiculite) and water.

STEP-BY-STEP

1. Build a styrofoam mould from 2" polystyrene insulation to create the planter shape. Use a utility knife or handsaw to cut the required form pieces to size. Wear safety gloves when using a utility knife.

2. Assemble the four sides and bottom of the outer mould using 3" deck screws and duct tape. Make sure that the inside corners are relatively square.

3. Assemble the four pieces of the inner mould in the same manner.

4. Place the outer mould on a piece of plywood so that it can be moved prior to the hypertufa setting.

5. Mix the hypertufa material: combine equal portions of Portland cement, peat moss and sand. Sift the peat moss through a piece of hardware cloth over a bucket to remove large particles. Thoroughly mix the dry materials together before adding water. Gradually add water to create a moist paste-like mixture. The mixture is ready when drops of water can be squeezed out by hand.

6. Coat the inside areas of the form with Vaseline or oil for easy removal of the mold. Set two pieces of 2" ABS pipe cut to 2" in length on the base of the form for drainage.

7. Pack the hypertufa mixture onto the floor of the mould to a depth of 2". Pack firmly or air pockets will later cause the form to fall apart.

8. Set the inner mould onto the hypertufa floor, centering it inside the walls of the outer mould. Use small pieces of styrofoam as temporary spacers to help centre the mould. Then fill the side walls, packing the material down as you proceed until you reach the top rims of the moulds.

9. Cover with plastic for 24 hours. When the hypertufa is hard to the touch, the forms may be removed. Be patient - removing them too early will cause the material to fall apart. You may enhance the aged appearance by roughing the surface with a wire brush. The planter will continue to dry and cure for four to six weeks. During the curing process, protect from direct sunlight and freezing temperatures. A daily rinse with water will help to neutralize the chemicals in the hypertufa.

The cedar trim around the planter top is optional. Use 1" cedar to construct.

WHAT YOU'LL NEED

Material
- large pail for mixing 4544-390
- gloves 5526-610
- Vaseline or oil
- duct tape 5540-220, 2611-273
- 2" styrofoam or 2" x 6" rigid insulation (or equivalent)
- 2" diameter ABS pipe, 2 pieces 2" long
- peat moss, 1 cu. ft. 5053-121
- Portland cement, 1 bag 2622-095
- sand mix, 1 bag 2622-567
- 1" x 6" cedar, 8 feet (optional)

Tools
- utility knife 1034-165
- measuring tape 1048-832

Optional tools for cedar trim
- hand saw 1063-823
- jigsaw 1368-489
- mitre saw 1347-046
- table saw 1346-699

PARTS

A end pieces - (2) 12" x 8" high
B side pieces - (2) 28" x 8" high
C floor - (1) 28" x 16"
D drainage pipes - (2) 2" dia. x 2" long
E ends and support - (3) 4" x 6" high
F sides (2) 20" x 6" high
G side trim - (2) 3/4" x 1 3/4" x length (measure to fit)
H side trim - (2) 3/4" x 1 3/4" x length (measure to fit)
I top trim - (2) 3/4" x 3 3/4" x length (measure to fit)
J top trim - (2) 3/4" x 3 5/8" x length (measure to fit)

These two more elaborate projects demonstrate the versatility of hupertufa that can be sculpted, hand moulded, sand cast or formed in a mould.