Standard Recipe (all measured by volume) 

2 parts Portland cement 

3 parts peat moss (sieve for finer quality) 

3 parts vermiculite, sand or gravel Water (enough to moisten to a drop or perlite cookie consistency) 

Dividing the mixture into smaller batches makes it easier to mix. You can store the mixture in a closed plastic bag placed in an airtight container such as a garbage can. 

Tougher hypertufa: 

To the regular mix above, add 1 to 2 cups of acrylic bonding agent, such as Acryl 60 or Embond to the water. This agent can also be added to ready-made mortar mix to mend cracks and broken troughs. Also add plastic fibers or fiberglass, such as Hi-Tech Fibers, for reinforcing. Use about a handful (1/10 oz) to a gallon of the mix. You want to put enough in so you see a large number of fibers in the mix. Add them a little at a time while mixing or you’ll get “fur balls.” Once the trough is dry, an open flame such as a soldering torch can burn off the fibers which jut out. 

If your looking for “How many bags of what to buy”; 30 lbs. of Portland cement, 1 cubic foot compressed peat moss, and 1.5 cubic feet of perlite are about right to make one small to medium trough approximately 8x12x12". 

Mixing:

Measure the dry ingredients into a large container such as a wheelbarrow. Mix them thoroughly before adding water. While stirring the mixture with a shovel or concrete trowel, slowly add the water mixture. Use as little water as possible, but make sure the mixture is equally wet. Test the mixture for proper consistency by taking a handful of mix after each addition of water and squeezing it into a ball that will hold together when you open your hand. A little water can drip between your fingers. THE AMOUNT OF WATER USED HAS A GREAT EFFECT ON THE FINAL STRENGTH OF THE TROUGH. 

Building: 

Using one hand on the outside of the mold for support, firmly place handfuls of the mix with your other hand and pat them to the mold or form. Begin at the bottom and work up the sides. Make the bottom of the mold about 2" thick and the sides 1" to 2" thick . . . a 12x24x12" trough will require 2" thick walls. Test the thickness with a nail or wire. You can add drainage holes with your finger or build around dowels or pencils and removing them when the mold is partially dry. 

When using rectangular forms, start inside the mold and work outside, building up the corners a little thicker to allow for strength. Make sure the bottom is perfectly flat or the trough will rock. For an upside down “bowl” form, cover the form with a large garbage bag (eliminate as many wrinkles as possible) and evenly apply the mixture over the plastic-covered form. Be sure to make what will be the bottom when finished thick and flat enough for the trough to sit level. Add embellishments such as shells, sticks, whatever to your trough at this time. Once the trough is the way you want it, cover it with plastic sheets. Periodically mist the trough surface to keep it moist, recovering it after misting. 

Curing: 

The first stage of curing lasts about 2 to 4 days. Total drying time will depend on humidity and temperature. After 24 hours you will want to test the mold. Gently uncover the trough and feel it. If your finger scratches it, cover it and wait another 12-24 hours. If your fingernail doesn’t scratch it, try a screwdriver. If the screwdriver scratches the surface with some difficulty, your trough is ready to be unmolded. DO NOT UNMOLD TOO SOON. Generally, upside-down troughs and small, foam-form troughs are ready after 36-48 hours. Large troughs in foam forms are ready in 24 hours. 

Once unmolded, use a wire brush to remove some of the flaws of construction. You can use an assortment of items to round corners and put scratches in the trough; hammers and chisel, paint scrapers, putty knives, any strong tools you feel will do the job. You can carve designs or your name and date. Use the wire brush to remove loose material and add a final finish. 

Let the trough cure for at least a month at room temperature. During this time keep it moist and wrapped in plastic. BE PATIENT, this will make your trough the strongest possible. Curing will take longer at cooler temperatures. Once the trough is cured, remove it from the plastic and let it dry thoroughly. You will know it is completely dry if it sounds hollow when tapped. 

The cured concrete will be very alkaline. You will need to “age” the trough for a few months to dissolve the free lime from the cement. This can be done by leaving it out in the rain or watering it periodically with a hose. You can speed up the process by soaking the trough in a solution of potassium permanganate, vinegar or dilute acid (a mix of 4 parts water to 1 part muriatic acid) for a day or two. 

You may want to make your troughs in the fall or winter, This will allow enough curing and weathering time before planting. 

The Internet also has several sites on hypertufa. 

OTHER IDEAS: 

Use a small trough as a candle holder. 

When making a container using a “bowl” container, try adding mixture unevenly so it looks more “rocklike.” 

Try embedding a surface layer of sand in the wet hypertufa to give it a “desert” like appearance. 

Use your trough as a water garden container. 

Although originally used for alpine plants, try planting succulents, or a combination of thymes, moneywort, and nasturtiums. 

Add granite grit, sold in feed stores for poultry, to improve drainage in soil mixtures.