Hypertufa is composed of a mixture of portland cement, peat moss and one or more of the following: perlite, vermiculite, or sand. Fiberglass fibers or an acrylic hardener may be added to the mix to improve strength. Dyes are available to add color if desired. Finally, water is added to obtain a workable consistency and to start the hardening process of the cement.
Portland cement is the glue of hypertufa. It is the main ingredient in concrete and is composed of a mixture of limestone and clay. When mixed with water it dries to a hard solid mass. It is commonly available at home centers and hardware stores. When making hypertufa, use only portland cement. The various concrete and mortar mixtures will not provide the same results.
Because of its high lime content, portland cement can be very caustic. Care should be taken when working with it. Always wear waterproof gloves to avoid drying and irritating the skin. Portland cement and other materials used in hypertufa are very dusty. A dust mask will help to keep from inhaling these materials. And although hypertufa containers are relatively lightweight, portland cement itself is very heavy. It is commonly available in 94 pound bags and help may be required to lift and move these bags.
Peat moss is the other material common to most hypertufa recipes. Peat moss is lightweight and absorbs and holds water. In the hypertufa mixture, peat moss provides soft spots where roots can grow. Some people experience an allergic reaction when working with peat moss. Again, gloves and a mask will provide some protection from the dust of the peat moss. Some references indicate that long-fiber sphagnum moss can be substituted for the normally used milled peat moss. Both types are readily available at garden centers.
Perlite, vermiculite or sand can be used as the third main ingredient in hypertufa (Fig. 2). Perlite is commonly used to improve drainage in potting soil. It is a natural material made by heating a form of volcanic lava to high temperatures until it pops like popcorn. The resulting product is very light weight and will add bulk to the hypertufa recipe without adding weight. It provides a coarse finish to the hypertufa. Perlite is readily available in garden centers and home centers.
|Figure 2. Sand, perlite, or vermiculite are mixed
with peat moss and
portland cement to make hypertufa.
Vermiculite is another material used in potting soils. It is derived from the mineral mica, which when heated, expands similar to perlite. It is also very lightweight. Vermiculite absorbs and holds water. The fine grade is usually found in garden centers, although a medium and a coarse grade may also be available. The coarser the grade, the coarser the final finish of the hypertufa.
Sand can be used in place of perlite or vermiculite. Many types are available, ranging from childrens sandbox sand to high quality builders sand used in construction. All types provide good results when used in making hypertufa. Sand on a volume basis is much heavier than either perlite or vermiculite. When used in making hypertufa, the resulting container will be correspondingly heavier. Several types of sand can be found in garden centers and in the construction department of home centers.
Hypertufa objects can be made stronger by adding acrylic hardeners or fiberglass fibers to the mix. Acrylic hardeners, found with cement products in home centers, is a liquid mixed with the hypertufa ingredients. As the hypertufa dries, its strength is increased by the hardener. This will increase the durability of the object.
Strength of hypertufa, especially for larger objects, can also be increased by adding fiberglass fibers to the mixture (Fig. 3). These fibers have a very high tensile strength, which helps hold the hypertufa together. Fibers are an economical alternative to the acrylic hardener. The fibers occasionally can be found in home centers and construction supply stores. If not, they can be made by separating the fibers of fiberglass matting used for auto body repair. The matting is inexpensive and readily found in any auto supply store. Caution should be used when separating and mixing the fibers. They are made from very fine glass fibers which can irritate the skin.
|Figure 3. Fiberglass fibers add strength to the hypertufa.|
Large projects can be reinforced by embedding chicken wire into the hypertufa mix. The chicken wire adds strength and helps prevent cracking. However, it can be difficult to fully embed and conceal in the hypertufa.
Various dyes are available which can be added to the hypertufa mixture to alter the color. Hypertufa without dye dries to a greyish color similar to normal cement. Dyes come in liquid form and are added to the water mixed with the hypertufa. The more dye added, the darker the color. These dyes have the advantage of permeating throughout the hypertufa and will not flake or peel off like paint. However, unlike paint, the dyes are available in a limited supply of colors. Colors normally found at home centers and hardware stores include buff, charcoal, terra cotta, red and brown.
Gardening with Hypertufa
Final Curing and Aging