When I finished my last workshop, a root over rock planting using multiple rocks, David Fukumoto wrote: "so what's next--Hypertufa?" I had never heard of the stuff and this piqued my interest. So I began my investigations into this interesting material. Tufa is a naturally-occurring rock formed by the precipitation of carbonate minerals from bodies of water. The most spectacular examples in the United States are the formations of Mono Lake in California.
"Hypertufa" is a recently invented anthropic (man-made) rock-like substance originally created as a substitute for natural rock in alpine gardens, and for use in English gardens, which used a natural rock which was becoming prohibitively expensive. Like concrete, hypertufa uses Portland cement as one of its ingredients. But the other two are not sand and gravel but peat moss and Perlite (or vermiculite).
Advantages of hypertufa over natural rock include:
1. Light weight
2. Ease of sculpting and uniformity of texture
3. Resistance to unpredictable fracturing
4. Low cost and widely available ingredients
5. Appearance of natural rock
6. Frost-fracture resistance
7. Ability to employ coloring agents
So, a couple weeks ago I made my first batch of hypertufa, using a 1:1:1: mix of portland cement, peat moss, and Perlite (ratios by volume). The dry ingredients were mixed thoroughly (use gloves and a mask), peat clumps broken up, and then water added slowly to make a mix of "mud-pie" consistency (not as wet as concrete), and formed into an amorphous log about 10 inches long by 4 inches wide. No mold was needed. This was wrapped with plastic wrap and allowed to partially cure for 48 hours at room temperature, after which sculpting began, using a cordless drill and masonry bits, an awl, a small stone chisel, and small hobby saw. The base was sawed flat in one minute using a curved wood saw of the type used to trim small branches around the yard. The sculpting went very easily--like drilling through butter-- but became harder after a week or so of curing. Still, it was easy work compared to natural rock. Only one minor fracture occurred which was easily repaired with epoxy. In retrospect, I probably could have started carving after 24 hours. One has a window of perhaps 24- 96 hours to do the easiest work.
I decided to sculpt a columnar structure with a deep saddle high on the right side to use for a planting. First, though, I soaked the "rock" in a vinegar solution to rid it of excess alkalinity and rinsed thoroughly. I then planted the "sumo" schefflera in the saddle.
Traditional Japanese bonsai ("tree in a pot") generally does not use
rocks. The less formal
Natural rocks, while often beautiful, are rarely of perfect size and shape and are often difficult to sculpt. For those who are interested in utilizing rock in their compositions, I believe hypertufa has great potential as a rock substitute, either as a decorative element or for planting.
I plan to experiment further with coloring agents, recipes that use less portland cement to further reduce weight, techniques to replicate the holes crevices etc. in natural tufa rocks, additives like decorative pebbles, etc. Results will presented in a subsequent report.
- - - George McLean, January 16, 2014
|COMMENTS BY DAVID:
I congratulate and thank George for a great preliminary report. Hypertufa has long been on my "to-do" list but I never got around to it! The Journal is fortunate to have George as a contributing writer with a bit of time on his hands and a lot of capabilities that are being wasted if he doesn't have interesting challenges!
When the Fast-Track Study Group began rock sculpturing, George helped with a pioneering effort that inspired those who followed. He struggled a bit but was successful. With his enthusiasm soaring, I introduced him to a much more complex challenge to create a landscape inspired by Chinese Taihu-type rocks. He took the bait and almost regretted that he bit off more than he could handle. But once he got his "second wind" he did a great job!
If you look at the progress being made by those in the Beginner and those who graduated into the Fast-Track Study Group, anyone would be amazed! I'm delighted and proud of each and every member who are willing to accept help to learn, but who reciprocate by sharing their successes, failures, and efforts for all to see and learn. By sharing and trying to teach others, the members of the Study Groups are learning the most and I invite more to join us in creating a Tropical and True Indoor Bonsai community!
By now, you'll recognize that our community is very different from the traditional Japanese temperate climate outdoor oriented bonsai community! Learning that type of bonsai can be painfully slow and most classes tend to create a dependency. There is a low success rate. Only a very small percentage stay on and become active members because of the very low success rate. In contrast, the success rate for True Indoor Bonsai is extremely high!