Hypertufa 101: Mixing, Molding, and Making Your ContainerBy Jill M. Nicolaus (critterologist)
August 30, 2012
You've made up your dry mix, chosen your mold, and set up your workspace. Now, it's time to get your hands into it and start creating!
For a list of materials and instructions on setting up your project, see Hypertufa 101, Part 1.
When we returned from our party break, we put on our gloves and dust masks and poured our dry mix into shallow mixing troughs and a couple of dollar store kitty litter pans. The buckets were then used to add water, a little at a time, while mixing with gloved hands. The texture should be pasty but not soggy, like a good mud pie. You can test the consistency just as you would for nicely moistened potting mix. When you squeeze a ball of it together, it should stay together and not crumble when you open your hand. If it crumbles, add more water. If water dribbles out, add more dry mix.
Start at the bottom and work your way up. You want it to be at least an inch and a half thick for strength, two inches for larger pots. Strengthen large projects by embedding chicken wire or fiber mesh in the layer of 'tufa and adding fiber or acrylic concrete fortifiers to the mix. Pack the mix tightly, like you're making a snowman and you don't want it to melt in the sun that afternoon. It's almost impossible to over-compress the mix, but you don't want to be too gentle and end up with a crumbly pot.
Build up the sides of the container with handfuls of ‘tufa, like packing snowballs together to make a solid snow fort. As you go along, you can check the depth of the ‘tufa by sticking a bamboo skewer into it. If you're making an "innie," the surface you're packing doesn't need to be especially even because it'll be hidden when you plant in your pot. If you're making an "outie," the surface will show, but one of the beauties of hypertufa is that lopsided containers or uneven textures often make the most interesting pots. Don't forget to poke a drainage hole or two through the bottom!
Seal your pot inside a big plastic bag and let it cure for the standard 24 to 48 hours. Although I'd heard all sorts of concerns about trying to transport pots several hours after making them (we had dinner together after our workshop), this didn't seem to be a problem. However, the pot will be quite fragile at this point, so use a light touch and be careful not to drop it. If you lose a corner or crumble the rim a bit during the process, no worries, it will just add to the authentic "aged" look of your finished pot.
Those who un-molded their pots the next day seemed to have less trouble with the molds sticking than those who waited two days. Plastic bags (sprayed or not) and oil-sprayed cardboard seemed easiest to remove; some other containers had to be cut and peeled away from the ‘tufa surface. A cheap serrated knife works well for cutting through most molds without cutting too much into the ‘tufa. You can go over the surface with a wire brush to roughen up the texture if you like.
Now the pots need to be kept moist while they cure for 4 weeks, yes, 28 days! You can accomplish this several ways, but the easiest is to submerge it in a bucket or tub of water. I used an old, watertight trash can. Lower the pot in carefully and support it from the bottom; if you grab it by its rim, it's too easy to break off a piece. Before you plant your container, you'll also need to soak it in several changes of water to leach out the lime, or simply leave it outside for a season and let nature do the work.
If you do this as a group project, be sure to post follow-up discussion and photos as you all un-mold and later plant up your creations! All the ideas we generated together gave us confidence as well as inspiration for about a hundred more hypertufa projects we wanted to try at home, on our own.
Whether you host a workshop or dive in on your own, try your hand at hypertufa. It's both easier and more fun than you may think to end up with some great looking containers!
Hover your mouse over images and links for additional information.
A big THANK YOU to the Mid-Atlantic Gardeners who contributed their creativity and enthusiasm to this venture. Thanks also to Ric & HollyS for sharing the images of his footed container at lower right. All other photos by Jill M Nicolaus.