Hypertufa

"The internet lists more than a thousand hypertufa sites which is a pretty good barometer of the forms popularity. Here are two that have good recipes and results.

www.efildoog-nz.com offers plenty of examples of hypertufa work, with pictures, background and the history of hypertufa, a well researched material and tool list and hypertufa recipes.

www.backyardgardener.com offers a variety of blends for making hypertufa and lots of links to other horticulture sites including one on trough gardening that hypertufarists will enjoy".

Information on Hypertufa - Instructions - recipes - Other Concrete Products

On a visit to Efil Doog you will encounter tubs and other items I've made here in the garden from Hypertufa.
Here is a bit of background information and hopefully some helpful hints on making your own garden tubs and pots.

Hypertufa containers are made from commonly available materials and can be easily made by most gardeners, thus providing a natural, attractive alternative to expensive purchased tubs and pots. One of the great advantages of containers and container gardening is that it offers the ability to provide exact soil mixes and conditions for particular plants. These can be tailor-made by the addition of specific fertilisers, soil conditioners and change of environment. The containers can be shifted from sun to shade and moved to protect from frost and wind. Of course they offer an alternative to those gardeners restricted by lack of garden space in small suburban sections and apartment. Tubs are also excellent for general use in gardens offering special areas of interest and tasteful features.

Hypertufa is aesthetically compatible with most building material and paving and does not look out of place in garden situations. It looks old and attracts lichens and mosses and has a natural look entirely compatible with plants and shrubs in the garden. Hypertufa tubs are very plant friendly. The bulky and porous wall thickness acts as a reservoir for water from which the plants can drink between showers and waterings. Being porous it allows for easy passage of air to the root systems - a feature often disregarded when using terracotta and plastic pots.

Trough gardens are excellent for elderly gardeners who can no longer manage the terrain and conditions of more conventional gardens. Pots and tubs can be elevated to allow easier gardening. Bringing the plants closer to eye level and taking the strain off the back the containers may allow us to continue growing our old plant friends.They can also serve useful temporary homes for cherished plants for those in transit or living in rented or mobile homes.

Hypertufa pots are suitable for many sorts of plants and are particularly good for cacti, succulents and alpine plants. In cool shady areas pots and tubs can provide great little special effects particularly bright glowing perennials or annuals potted up and tucked into shady green areas as a vivid contrast.

Hypertufa is a man made substitute for Tufa rock. Tufa is a spongy cellular rock found in limestone country and especially where water has been involved in the wearing and leaching out of the original materials to effect a porous spongy consistency. In many countries throughout the world this natural stone has for centuries been hollowed out and carved for tubs and planters. One of the obvious advantages of the material for me is its versatility. It can be used for tubs, pots, troughs, steps, benches, sculptures, seats, stepping stones and bird baths. When properly surface treated it gives the appearance of great age and ruggedness. No special tools are required and if you are prepared to give it a go yourself they are inexpensive and entirely original. A little work of art.

Materials and Tool list:

1. For a square or oblong tub you will need two cartons, one of them with smaller overall dimensions by at least 5 or 6 cm. Place the smaller carton inside the larger. There should be a gap of 5 or 6 cm between the walls on all sides. These cartons are your moulds. For round containers try different size plastic bags, old plastic basins, or buckets.

2. Concrete blocks, bricks or short lengths of heavy timber to fit flush against the outsides of the outer carton for support. This stops the sides bowing out under the weight of the material. For the inside of the container use any spare sand, soil, potting mix (anything bulky) to stop the inside carton caving in. Fill up the inside carton progressively as the walls are built up. If you are using plastic bags for moulds, place 4cm wide adhesive packaging tape around the outside to prevent bowing.

3. Pieces of broom handle, branch or 25mm plastic pipe about 5cm long are used for drainage holes. These can be carefully removed later on. One or two holes are sufficient for small pots, but for larger tubs and troughs at least 4 drainage holes are needed.

4. The ingredients in proportion by volume - 2 parts peat, 1 part sharp river sand, moderately fine, but not beach sand (because of salt and it is too fine) 1 part cement.

5. Tools - Plastic Sheet 1.5 x 1.5 metres, Wheelbarrow (optional), Trowel or spade, Rubber gloves, Tamping stick, 50 x 50mm about .5 metre long, Wire brush, Old hearth brush, Water container or hose. Well now we have it altogether, let's start!

Lay the piece of plastic sheet on the garage floor. Place the large carton in the middle of it.
Place the concrete blocks against the outside of carton. Mix the ingredients in the wheelbarrow or on the floor. Quantity depends on the size of the envisaged container (use your judgement). After mixing the dry ingredients thoroughly add sufficient water to make a sticky stiff mix - not runny but about mud-pie consistency, if you can remember back that far. Now stand the drainage plugs upright on the bottom of the carton and place a layer of the mix on the base and tamp it down giving special attention to the corners and around the drainage plugs. Aim for a thickness of 5cm for small to medium size tubs.

Take your smaller carton and place it on the layer of mix in the bottom of the larger carton. Make sure it is equally spaced on all sides. Then one quarter fill it with sand or whatever you have. This will stop the inside bowing in and the carton floating up. Now fill up the wall space between the cartons. Use the tamping stick to work it into the corners as you go to get the air bubbles out. Make sure you tamp the outside walls well. Keep building up the sides with mix, adding sand to the inside carton for support until you have reached the desired height. Leave it and don't come back for at least 24 hours.

Finishing: Next morning dash out and have a look at your handiwork. Yuck! Wet cartons. But that's just what you want. First, scoop out the sand from the inside carton. Then CAREFULLY peel off the inside wet cardboard and discard. Now the outside. Remove the concrete blocks and carefully finish peeling away the outside carton but don't worry about the bottom.

DON'T TRY TO MOVE OR TIP THE CONTAINER AT THIS STAGE - YOU WILL LOSE THE LOT !

Now the tricky bit. You will notice that the walls are rather smooth, in fact just like dark wet boxed concrete. This is not on. We want the walls to look aged and weather worn. This is what we do. Using a wire brush or a special scraper (see below) we very carefully roughen the sides, top and inside rim. I prefer to round off the corners and edges as well. Don't worry about a few nicks and scratches and small holes. These help to give it a natural look. You may wish to carefully scratch in your own design or special texture. Having shaped the outside to your requirements, gently give it a good brush with a hearth brush.

The container should be left for at least a week to allow it to cure and set hard. Give it a light sprinkling with water initially 3 hours after moulding and therafter every couple of days to assist the curing process. It is most unwise to lift it until it's entirely set, but if you have to shift it only do so by sliding or dragging it across the floor by means of the plastic sheeting. The mix left over can be used for stands for the containers. Either press it into pottles or plant pots or roll it into flattened balls. Using builders' adhesive these can be attached to the container base as feet at a later stage.

If you want a really large container try to make it close to where it is to be used. Larger tubs can be made by joining cartons together with plastic adhesive packaging tape. Line the inside with thin plastic sheet to prevent the adhesive integrity of the tape being lost when it gets wet. For a large pot you should also add reinforcing in the form of No. 8 wire, or mild steel rods. Two rings, one just above the base and the other about 5cm down from the top should be sufficient.

You can also use the same mix by hand moulding it to the inside surface of plastic bowls, buckets or basins avoid using containers with any undercut. This technique is fine for low sided vessels but not really suitable for high sided or large tubs etc. It is wise to coat the inside of the plastic mould with silicone spray or a sheet of thin polythene to act as a release agent. Wearing rubber gloves press the mix firmly into the bottom and sides of the mould (no less than 30mm thick) having firstly placed the drainage plugs on the bottom. Leave the container at least 4 days (depending on the weather) to set. Finish as described previously having carefully extracted it from the mould.

Conditioning

As the pots age in the garden the peat will weather out leaving the surface pitted and porous adding to the aged effect. Depending on the site you decide to display your trough you can expect in time to have lichens (dry sites) and moss (wet sites) using the surface as their home. A coating of milk, yoghurt or a slurry of cow manure enhances the early growth of moss.

Alternative Mixes

Alternative Hyper Tufa mixes can be made by using pine needles, chaff, fine bark mulch, vermiculite and the fine debris washed up on the beach containing twigs, seaweed, shells and bones etc. All these can be used in place of peat. Materials originating from the beach should be washed to remove salt. You may also add a slow release fertiliser into the mix, say Magamp.

The mix proportions can also be altered, for instance one may prefer for the sake of strength to use equal proportions for very large troughs, especially if they are to be moved. I would also use this mix for sculptures and steps, maybe adding small metal chips for the steps. Hypertufa gives a soft tread and old look to steps that you don't get with plain concrete.

Sculptures from a block of hypertufa

To use Hypertufa for sculptures pour the mixture into a carton to form a block. Leave overnight, at least fifteen hours, to get a partial set - this will depend on the weather. Remove cardboard from the sides and leaving where it stands proceed to carve away. It won't remain forever in this partially set state, so be prepared to finish in one sitting. The design should be simple without small detail or thin edges. Use a knife and wire brush. Work carefully and when finished leave on the spot for a week or so to firmly set. You may find it easier to work if you cast your original block on a raised bench or box.

To make stepping stones place metal flashing on its edge to form a circle or oval. Shape and hold the metal strip with wooden pegs driven into the ground on the outside of the shape. The height of strip will depend on how high you want your stones. Pour your mix (as above) into the mould and the following day remove tin, shape and round off the edges with a wire brush. Do not walk on them for a week. Sprinkle with water each day if you can.

Decoration of Hypertufa Tubs

Decorated with large leaf rhododendron motif. The habitat for a "tree man" (work in progress bonsai) which will take many years to reach the desired state. This is an eight year old Liquid Ambar Styraciflua a deciduous tree with lovely autumn colour leaves. Can grow to 50 metres high by 5 metres wide.

Method:

Follow the basic Hypertufa trough process for using two cartons but with a 1 part sand 1 part cement, part peat. Select leaves that have well defined vein and leaf characteristics on the underside of the leaf. Glue the leaves face down with latex cement onto a strip of heavy paper which is long enough to line the inside of the outside carton and wide enough to cover the height of the outside carton wall. Over these leaves lightly sellotape a single covering of Gladwrap or similar very thin film ( having two people for this process helps ). Fix to the inside wall with a little sellotape.

Using a moist, smooth mixture carefully place into the mould in the same way as normal (inside outside carton process) but be even more careful to tamp the mix into corners and around the drain holes and walls to make sure air pockets and voids are eliminated. In doing so don't tear the plastic film or damage the leaves.

Leave for 24 hours then carefully peel away the inside carton having already removed the inside packing and then the outside carton and leaf pattern. Do not worry about the cardboard on the bottom as this can be removed when the tub is properly cured and can be moved.

Do not attempt to move the tub for at least 6 days and even then be very careful until it is properly cured and hard.

The top and inside of the tub should be wire brushed immediately after the carton is peeled away within 24 hours the leaf pattern being left smooth of course.

Hypertufa Grots

Grots inhabit only dark forest floors and gloomy garden corners. They are seldom seen individually or even in small groups. The are all quite deficient in social skills. It is best not to disturb them.

Use large plastic planter pots as moulds. Place a supermarket plastic carrier bag inside the pot and drape the top and handles over the outside of the planter. Smooth out the worst of the folds.

You will need probably want to experiment by first making just one. Later you may possibly make them in batches. My experience is that seven heaped digging shovels of cement, an equal amount of sand and ten or eleven shovels of peet ( sieved to avoid lumps) will make between five to seven grots. This is a rough guide only. The planter pots I use are 280 mm high and 220 mm across the top.

Always mix the dry contents thoroughly before adding the water. Mix up the hypertufa mixture (1 part cement 1 part sand 1 � parts peet by volume with enough water to give a sloppy homogenous mix.

Place the mix into the pot with a small shovel filling it up gradually and tamping down as you go ( a piece of wood 50mm by 50mm across is fine ). Occasionally give the top of the shopping bag a big of a tug to prevent the mix flowing into any folds. Fill to 1cm from the top - this makes them much easier to turn out when set.

Leave the newly poured heads for 24 hours and then carefully turn them out (the pot will be upsidedown) onto a surface where you can continue to work on them. At this stage they must be handled very carefully. Avoid putting any stress or weight on the edges particularly.
Using a wire brush round off the top corners to eliminate the flat flower pot shape unless of course you want the Bart Simpson look. Remove with the brush all smooth surfaces and plastic bag fold marks. Leave for a further 24 hours.

Using one part cement and one part sharp coarse sand carefully mix and slowly add water until the mix is plastic, slightly stiff but workable (not wet enough to run over the place and not dry enough to crumble. If it is mixed properly and you work fast enough and you give it an occasional stir you should be able to finish 5 or 6 heads. So experiment initially on one head and then estimate how much you need to mix, related to how fast you work.

Wet the face surface and with gloved hands mould the faces on. Eyebrows first then the nose and lastly the mounds for the eyes into which you press the glass eyes (large marbles are good). Make sure the eyes are embedded more than half way into the eye mounds and mould over for good retention. You can, I suppose make the facial components in any order. I find it less stressful the way I've described. You can of course give them mouths. I don't want that for my faces (makes them look too human) but I've tried it and it's possible.

When placing the facial features make sure the mix is firmly pressed onto the surface of the head. Smooth off round the edges of the eye mounds etc.
Lightly sprinkle with water after 4 or 5 hours and once or twice over the next couple of days while they are curing.

After four days they can be placed into the garden where they will continue to harden for some time.

The heads can be coloured. I tint mine by painting with a very very watery coat of green acrylic paint which appears to lighten as the concrete dries and is absorbed into the material as it is curing. Grots really resent being painted white or bright colours. Grots pay you back if you don't use natural colours.

Grots at Play

Grots Totem Pole

Leaves Cast in Cement and Sand

Concrete leaves as a fruit bowl decoration

This method is suitable to duplicate interesting leaves of all sizes in a medium which is inexpensive and simple to use. The principle can be used for all leaves which have a well defined veining and interesting characteristics. Painting them is fun and they are great as fruit bowl decoration or ornament in their own right.

Place the leaf face down on fine dry loose sand and press gently to a natural curvature. Over the leaf place a smooth layer of glad-wrap thin plastic film.
Mix one part sand and one part cement with water to a smooth biddable plastic consistency free from air bubbles.
With a small spatula carefully but firmly smooth a 5mm to 7mm layer of the mix over the leaf surface avoiding air bubbles. Define the leaf outline and taper the mix on the leaf edges. Leave to cure for at least 48 hours but after 2 or 3 hours have elapsed give them a light spray of water and repeat this a couple of times during the curing process.

When the leaf is dry the edges and back of the leaf can be carefully sand papered in a manner that retains the true shape of the original. The top surface of the leaf should not require any finishing although small voids may require filling with something like "No-more-gaps".

You can use Artist Oil colour or acrylic to paint them but the gloss oil colour surface is preferable. Suitable deciduous leaves can be painted in bright autumn colours.

This principle can be used for larger leaves such as Gunnera, rhubarb etc. although rhubarb stems need to be sealed with a little plastic film to prevent the cut exuding the sweet juice which inhibits the concrete setting. A thicker layer of cement and the addition of chicken wire or other reinforcing material is essential. Consider the thickness required in the light of strength, size, aesthetics and intended purpose. You may wish to use your Gunnera or rhubarb leaves for seats, stepping stones, garden features, for water to trickle down into a pond or cemented to the surface of a hypertufa tub.

Remember that you are duplicating the reverse side of the leaf and a well defined veining and characteristics are preferable.

Rhododendron Grande Spec leaves. The leaf in the centre is almost true to actual colour. L. leaf is unpainted R. colour imagined.

A comprehensive booklet approximately 32 pages is available from:
Moss Green Garden,
Akatarawa Valley,
RD2 Upper Hutt.
N.Z.

Click here to get a text only version. But first ensure you have "Acrobat Reader" as it is in PDF format.

Hypertufa - Pots, Tubs, Troughs

Home Grown Stone

Press Journal Florida USA Sunday 14 October 2001

Information on Hypertufa - Instructions - recipes - Other Concrete Products

Decoration of Hypertufa Tubs

Hypertufa Grots

Grots Totem Pole

Leaves Cast in Cement and Sand