Our favorite garden accessory is our hypertufa birdbath. I always wanted a vessel with a wide shallow basin instead of the two-piece pottery ones you see for sale everywhere. Regular birdbaths served us well enough, but after a succession of broken and cracked tops, we wanted a better solution.
My friend showed me her hypertufa birdbath and I was sold. She was even kind enough to lend me her mold, a snow saucer! I’m indebted to her for sharing her creativity with me, and now I’m passing her secret along to you.
You’ve probably seen hypertufa items in other people’s gardens. They are rough-hewn vessels with thick sides and a coarse, gritty finish. Planters are the most common type of hypertufa vessel. Some people make “old man” faces out of it. The best use of hypertufa, in my opinion, are custom birdbaths and ultra-wide succulent basins. If you want a large, stone-like container that’s cheap, lighter than stone and durable, and you don’t mind making a mess to get it, hypertufa is for you.
Why A Custom Birdbath?
According to the National Audubon Society (NAS), a birdbath should accomodate song birds’ preferred water depth of 1 to 2 inches. Any deeper and most songbirds will not venture in.
But that’s not all. Metal birdbaths can get scorching hot, glass ones are too slippery, bright colors are off-putting, small ones dry out, and pottery ones often break if they freeze. Many have steep sides, which make wading impossible for small birds. In other words, a lot can go wrong with commercially available styles and designs.
NAS also recommends setting a few flat stones in a birdbath. Their familiar presence help birds judge depth. I keep a few saucer-sized stones about an inch thick in ours. In winter, they disguise a submerged heating element, and the displacement they cause reduces the volume of water the heater must handle.
Finally, an extra-wide basin allows more birds to drink or bathe at once. Its gentle depression mimics a natural puddle. Judging by how much the birds hop in and out of it, they feel safe there. Best of all, I like the aesthetic appeal of a naturally “aged” patina on a wide vessel.
What is hypertufa made of?
Hypertufa is a mix of water, portland cement, peat moss, and either perlite or vermiculite. Recipes for tougher vessels recommend vermiculite rather than perlite. They also add fibermesh, a synthetic reinforcing fiber used in concrete work. It looks and feels like soft fluff. It’s readily available online. Some recipes also add sand, but I didn’t.
If your hypertufa container is going to hold water or get left out over the winter, I strongly suggest you add fibermesh. Sand is up to you.
There are lots of YouTube videos showing you how to make hypertufa. some better than others. I suggest watching several, even the bad ones, to get a feel for the general process. (Just skip the slow parts.)
In addition to YouTube here’s a Fine Gardening article I found most useful. Although their demonstration is not for a birdbath, the process is the same. https://www.finegardening.com/article/make-your-own-hypertufa-container
If you want to get fancy, you can try making a patterned surface from bubble wrap, leaves or other materials. My instructions are for a basic, unadorned birdbath basin.
Before You Start
Choose a suitable mold. My friend and I used an old aluminum snow saucer. The outside dimensions of my birdbath measures 32″ across by 4.5″ to 5″ deep. The interior depression, which was the snow saucer’s diameter, is 27″ across. The saucer was placed upside down and the hypertufa molded over it.
At its deepest point the water level reaches barely 3 inches with most of the depth well under that. The birds bathe around the edges and avoid the center. That is where the fountain floats anyway, so it works out quite well.
Your mold will determine your basin’s shape and depth. Uniform thickness and density in the birdbath’s walls are more important than specific dimensions. Thicker is better for a water-tight vessel, so aim for an overall thickness of 1.5 to 2 inches. (My rim is 2.5 inches thick.)
Use whatever you can find for a mold. It need not be round. A shallow rectangular food tray would work. Other possibilities might be a pet’s wading pool, a trash can lid, or a maybe a paella or pizza pan. Plastic and non-rusting containers with a smooth finish and no lip or handles are best.
If you can’t find a mold or you want to make an unusual shape, you can pack wet sand into an upside-down mound in the shape you desire. Cover with plastic and proceed. However, be careful not to distort the sand as you pack on the hypertufa. I haven’t tried this but I”m sure you could make nice oval and kidney bean shapes.
Drain hole? Not recommended.
I decided to add a drain hole in my birdbath because I thought it would be easier to empty. In practice, we discovered a drain is not necessary; in fact it’s problematic. The hole is hard to keep watertight even with silicone sealant, a stainless washer and rubber plug. The drain also interferes with cleaning because the sealant doesn’t stick to the hypertufa very well. Therefore I do not recommend a drain.
It turns out tipping the bowl to empty it is very easy because hypertufa is lighter than concrete. We don’t use the drain at all; we keep it sealed. Once it starts leaking it’s a real pain to stop.
Supplies Needed:
- Large wheelbarrow or tub for mixing
- Container for measuring, such as a 4-gallon bucket
- Sphagnum peat moss
- Dust mask
- Rubber gloves
- Mixing hoe or large trowel
- Plastic drop cloth
- Several contractor-size trash bags
- Wire brush
- Builder’s level
- Short ruler or measuring stick
- Hose and water
- Flat piece of scrap plywood larger in diameter than mold
- Plastic or metal mold for birdbath, or coarse sand
- Small plastic mold for a pot, in case there is leftover hypertufa
- Vermiculite
- Portland cement (regular)
- Fibermesh/ concrete reinforcing fibers
Recipe
All recipes for hypertufa contain the same few ingredients but the ratios can vary. This is the recipe I used. Peat moss, vermiculite and perlite are available at nurseries and garden centers. Sand, Portland cement and fibermesh are available at masonry supply stores, some hardware stores, and online. Be aware that Portland cement comes in 1-cubic-foot bags weighing 96 pounds. You may need the help of a dolly or another person to move it.
Ingredient Ratios
- 1 part Portland cement
- 1 ½ parts sphagnum peat moss
- 1 ½ parts vermiculite or perlite
- 1 small handful of fibermesh per batch
Quantities (Dry)
- 2 gallons Portland cement (dry mix)
- 3 gallons peat moss
- 3 gallons vermiculite
- Small handful of fibermesh
Start with the above amounts. If you need more, mix at the same ratio. I do not recall how much volume my birdbath took. If you end up with leftovers, make a small planter to use it up. A bucket with gallon markings is helpful for measuring.
The demo photos show perlite in their hypertufa, which is white, instead of vermiculite. Either will work but I recommend vermiculite, which is light brown, for a more natural color and also greater strength. Save the perlite for lightweight hypertufa planters.
Prepare your mold. Work outdoors on flat ground that will stay shady all day. To discourage sticking, encase the plywood “base” with a trash bag and lay it flat. The plastic should not have wrinkles, as the birdbath rim will lay against this surface.
Turn your mold upside down on top of the plywood. Cover it with a second trash bag (or any large plastic sheet) pulled taut, making sure no big wrinkles are present. The plastic bag will allow you to remove the mold easily later. Mark your desired rim width on the base about 2 inches out from the mold with a few pieces of tape.
Mix up the hypertufa. In a wheelbarrow or tub, measure the peat moss, vermiculite, cement and a small handful of fibermesh. Break up any clods with your trowel or hoe. Slowly add cold water while the mix is turned. This is easiest with two people, one adding water and the other stirring. The peat moss initially resists wetting; it may take a fair amount of mixing to get it evenly moist.
Stop and test frequently by squeezing a handful of mix. When it seems uniformly wet and retains its shape without releasing more than a few drops of water, the mix is ready. It should be the consistency of wet mulch, but stickier.
Start molding. Scoop handfuls of hypertufa onto your mold, starting at the bottom and working upward. Move around the circumference, patting the mix evenly with your hands. Use a short ruler or stick to gauge thickness – you want it at least 1.5 to 2 inches thick all over.
Press down firmly to compact the mix and eliminate air pockets. Flatten the top (which will be the birdbath bottom). Lay something level across it to ensure it will sit flat. Smooth the sides and surface.
Without disturbing it on its base, wrap the finished hypertufa in plastic sheeting to retain moisture. Make sure it sets in the shade for 24 hours while it hardens. The longer it takes to dry and cure, the stronger it will be.
Unmold. After 24 hours, your hypertufa birdbath will be firm but still soft enough to work. Remove plastic sheeting. Carefully slide your vessel to the edge of the plywood, allowing you to turn it over. Remove the mold. You may have to pull on the trash bag to loosen it.
Brush surfaces with a wire brush to knock off crumbs and give it a natural texture. Be careful not to brush too hard or wisps of fibermesh will catch in the bristles. Rewrap well and allow to harden for another 48 hours.
Cure for three weeks. Unwrap and soak your birdbath periodically with a hose over a period of weeks to leach out all residual lime from the cement. This step is very important, as the highly alkaline lime in the curing cement can harm animals and plants. To speed this step along, every few days fill your birdbath with water; cover it completely (I used the plywood base for this) to prevent any animals from inadvertently drinking. Leave to soak at least 24 hours. Pour out the lime water away from vulnerable vegetation and repeat. Do this step multiple times. After three weeks of leaching, your birdbath is ready for use.
Place your new birdbath in position on a rock cairn, heavy duty iron plant stand, or any sturdy structure that will securely hold it. Alternatively you can place it on the ground, but we found doing so greatly reduced the number of birds willing to use it. Birds want a birdbath that is raised at least a foot off the ground so they can spot potential predators more easily.
Give the birds a few days to discover it. Once they do, I’m sure they will love it and so will you!
Keep it clean. Change the water often. Scrub interior periodically with a stiff bristle brush. Liquid additives made specially for fountains and birdbaths will help reduce algae and is harmless if used properly.
To clean out black mold or mossy gunk, remove the birdbath to work on it. Scrub well. Fill with a 10:1 solution of cold water to straight bleach or add 1 cup of bleach to a full basin of water. Either way, cover it completely while it soaks several hours or overnight. The basin water should look whitish afterward. Pour out, scrub any remaining residue (it will come off easily), rinse well several times, and refill. You should not smell any bleach.
While hypertufa isn’t fast, it is rewarding. Now you can make yourself some planters!
