Hypertufa
A sand cast hypertufa pot, inlaid with glass scallop shells. The corks in the bottom are to hold the drainage holes open while the cement hardens.
Have you heard of it? This is one of those projects that stuck in my brain some years ago as something I wanted to try.
Hypertufa is a light weight cement like material one can use to cast pots, stepping stones, troughs, bird baths, stones, and other garden ornaments.
Peat, sand, vermiculite, and perlite measured, and ready to be mixed.
You mix the hypertufa from Portland cement and a mixture of other materials more commonly found in potting soil, and then mold or cast it to your liking.
After 36 to 48 hours you unmold it, perfect the finish, and then allow the piece to fully dry and season for the next several weeks.
It finishes to look like stone. Tufa is a type of limestone frequently carved into pots and garden ornaments in Europe. Expensive, it isn’t easy to come by in the United States. Hypertufa can be cast to make lightweight containers and ornaments with a similiar appearance.
As interesting as the hypertufa pieces featured in hard core gardening magazines look to me, there was always a reason not to do it: too busy, too many materials, too complicated…. Do you have a project you have always wanted to do, but never quite got organized to try?
Here the dry cement has been mixed in. The next step is to add water, and mix it all into a slurry.
Well, I finally made the decision to try it. Blame it on the excruciatingly late spring we’re having.
I haven’t been out to do my usual spring garden clean up yet because of the cold weather, so I decided to at least give hypertufa a try… inside.
Last week a good friend and I went to the Home Depot in search of the materials. We brought a flat bed cart inside with us, and were so fortunate to find a young, strong, friendly and extremely helpful clerk who became our personal shopping assistant.
We had to traipse from one end of the Home Depot to the other to gather all of the materials. And thank goodness Kelley stayed with us, and enlisted his colleagues to help us.
They got their work out for the day! The Portland cement only comes in 96 lb. bags. The sand and pea gravel are packaged in 50 lb. bags. We finally located small 8 qt. bags of peat moss and perlite; but never were able to find the final ingredient, vermiculite.
Two cubic feet of vermiculite.
Home Depot had some large plastic tubs at a good price, and so we loaded five onto the cart. These have hinged lids which open down the center and fold back to allow access.
Kelley loaded the cement into a large, heavy duty trash bag for us, and everything else into the tubs. Sadly, I couldn’t take him home to help with the unloading. We ended up with about 400 lbs. of materials, including the sand I purchased for making molds.
Getting it all inside was a slow job, but the tubs helped enormously. At least they had handles.
It is important to wear gloves, goggles, and a dust mask while measuring and mixing the cement. A job ends up being easier when you first assemble all of the needed tools and materials.
The next morning, my partner and I headed to another Home Depot, some thirty miles away, which stocked the vermiculite and larger bags of peat.
I wanted the 2 cubic foot bag of vermiculite, and a large bale of peat. Thank goodness the vermiculite is light and easy to handle!
Now vermiculite is heated mica chips. It looks golden, a little more coarse than sand, and is feather light. Most potting mixes include some vermiculite.
This container is cast in a very large nursery pot, lined with a plastic bag. I hope that oatmeal box comes out OK….
Chemically inert, it promotes drainage in potting soil, but helps make hypertufa strong and light. Perlite, the little white pellets you see in most potting soil, is also used to make the finished hypertufa pieces light. Most recipes call for one or the other.
Because I found the perlite first, I bought it, and am using it in combination with the vermiculite. Once I’ve used up what we found on Wednesday I’ll probably switch to all vermiculite in future batches.
This is a stepping stone, cast in sand. I laid a mosaic design of glass marbles into the sand before adding the cement mixture.
Today I decided to mix my first batch of hypertufa.
I’ve read about several different methods for casting pieces, and wanted to try out several different techniques. I prepared a few sand cast molds, which are more free form and allow you to work and shape the hypertufa by hand.
After dampening the sand and hollowing out the basic shape I wanted to cast, I laid stained glass pieces into the sand. Next came the hypertufa mixture.
I’ve cast one solid stepping stone, and several hollow pieces which I’ll plant up in a few weeks when they have cured.
This is the mold for the container shown at the top of the post. See the glass shells set into the sides? The corks set in the sand at the bottom of the mold are for drainage holes.
I also prepared a plastic pot and several boxes with plastic bag linings. The hypertufa goes into the plastic lined mold, and then you either form the cavity by hand, or place another plastic bag and another, smaller mold inside to form the cavity.
Seeing how these first pieces come out, in a few days, will teach me which methods seem to work best.
This will be a trough, probably planted with succulents since it is shallow. It is large enough that I set the plastic bucket inside to support the long walls as they dry.
But for now, at least I know this is a process I can enjoy and can manage in my work room. Casting one’s own pots and troughs is far more affordable than purchasing glazed or terra cotta pots at the garden center.
And as a bonus, the size and design can be tailored to the available space in the garden and the needs of the plants you want to grow in them.
When I ran out of corks, I experimented with keeping the drainage holes open with sand…
Once I refine my casting technique, there are all sorts of interesting things I’d like to make. We’ll see how these first few items turn out, when they are solid enough to lift out of their molds on Wednesday.
I’m already making plans for the next batch…
These miniature daffodils bloomed today. So tiny!
Photos by Woodland Gnome 2014
Another project finished! These stepping stones are made by gluing the glass to a purchased cement block, and then grouting them into place with mortar. They can go outside when the weather finally settles.
Forest Garden 