I've made a lot of rectangular troughs over the last year and have been hungering for something more organic and informal to mix it up. I kept boring my wife with talk of the Guggenheim Museum crossed with a geode or scholar's rock. Some version of this design appears off and on in my sketchbook for the last few months. Above is a drawing from last week, with a note about a book mentioned on GardenRant that I want to read. Since I finally finished all of the troughs that I had orders for and have time to play (I mean do research and development) I freehanded an interior core over the weekend with some 2" rigid insulation board. I used spray adhesive to stick the layers together and shaped them with a large, sharp knife.
I skimmed the exterior of the form with joint compound to cover up the irregular surface of the foam. I trimmed away anything that looked like an undercut. My goal was a smooth core that could be pulled from the top of the final hypertufa piece with little resistance.
On Monday night I wrapped a couple of 1" nylon straps around the form to aid in pulling it out later on. I then mixed up a batch of hypertufa and applied about a 2" layer over the inverted, plastic-wrapped core. I packed the hypertufa mix as tight as I could on the core form. I've found that the more the hypertufa is packed the stronger it is. Casting hypertufa with only an inner core reminds me of turning clay on a potters wheel, only there's no turning and there's no interior (so maybe that's just my brain grasping at straws). It looked pretty boring when I finished up Monday night. I sealed it in plastic and hoped for the best.
On Wednesday, I gently rolled the whole thing over onto some foam scraps and pulled the core out with a flourish. No cursing for a change. I must be getting better.
Last night in a short, intense burst of sweating in a hot garage I rounded the rim edges with a trowel and gave the exterior a good wire-brushing. Using a wire brush helps to remove the cement that has migrated to the exterior, and exposes the perlite and peat moss in the mix. I'm not crazy about the chocolate chip cookie kind of look that it has initially, but I like the way that it dries to a nice weathered gray.
Sprayed with water and wrapped in plastic for a month, the trough will sit patiently (unlike me). The waiting makes me feel like some sort of insane baker with an oven that takes a month to bake. When it's cured I'll use the hammerdrill to put a few drainage holes in it. Planting will have to wait for cooler weather. In the meantime, I can use the core to make more, when and if it cools off.