About the SFMGA

Wednesday, April 29, 2009

HYPERTUFA PLANTERS – Stone look alikes you can make yourself

Materials:

  • Plastic sheeting or trash bags
  • Molds – plastic or ceramic bowls/tubs, foam coolers or nested cardboard boxes lined with plastic. Stainless steel is not easy to unmold.
  • Rubber gloves and dust mask
  • Large mixing tub or pail and trowel
  • Measuring container
  • Sifted peat moss
  • Vermiculite or perlite
  • Portland cement (must be Portland, not a quickcrete product)
  • Fibermesh reinforcing material (optional)
  • Cement coloring agent (optional: add ½ cup per quart of cement; add more if desired)
  • Water
  • Wire brush
  • Wood dowels, ½ to 1" or drill for drainage holes

Directions:

Determine if you want to use the inside or outside of mold to shape your piece. For beginners, using the inside is easiest; your planter will have smooth sides. (See notes below.) You can line the inside of the mold with plastic if desired to facilitate release. Finished planter should be 5-6" deep for best results.


Cover work area with plastic; work out of direct sunlight in a place you can leave your planter for a week or more to cure undisturbed. Do not allow planter to freeze during curing time. Large planters will be heavy, so you may wish to make them where they will be placed in your garden.


Put on your mask and gloves and mix one part vermiculite or perlite with one part peat in your tub. Blend in one part cement. Mix well. Add a handful of fibermesh, if using. Reserve a cup or so of the mixture. Begin to add water slowly, blending well. Add enough water to create a damp mixture that sticks together when you squeeze it. It should hold its shape. If mixture is too wet, you will need to quickly add some of your reserve dry mixture. It is much better to get your mixture right the first time as your planter will be stronger.


Beginning at the bottom, press handfuls of the tufa mixture into the mold so it's at least 1" thick. The larger the mold, the thicker the tufa should be. 2" is best for large molds. Too thick is better than too thin. Pat and tamp well to remove air bubbles and bond the tufa. Work your way up the sides of the mold, keeping consistent thickness on the sides. You can make the top edge smooth or textured. At this point, press a piece of dowel into the bottom to create drainage hole(s); leave in place as planter cures. You can also drill drainage holes once trough is dry.


Loosely wrap the mold in plastic for drying. Periodically uncover and mist the mold with water so it cures slowly. After 2-7 days, the tufa will be firm enough to remove it from the mold. Keep the planter covered loosely with plastic and allow it to cure another 1-3 weeks until completely dry. The longer the cure, the stronger the piece.


When the planter is dry, use the wire brush to do any additional shaping or texturing you desire. Any visible fibermesh fibers can be burned off with a small torch at this point. Because concrete is highly alkaline, it is best to let the planter weather a few more weeks, uncovered, before planting. Rinse it frequently with water to allow the lime to leach out.


To plant your planter, cover drainage holes with landscape fabric or plastic screening to prevent soil from blocking holes and leaking out. Fill with soil and plants as desired. Your planter should last for many years outside.


Notes:

  • You can choose to form your planter on the outside of your mold. With this technique you can create a textured outside surface. It is important with this method to make the top surface (which will be the bottom of your planter) level so your planter is stable on a hard surface.

  • Other molds to use for larger containers include nested cardboard boxes lined with plastic, or a Styrofoam cooler with a smaller box inside. These large molds will take a long time to cure.