Sep 4, 2015

Creating Hypertufa Pots

There are many blogs and websites on making Hypertufa but I feel many leave off important information and details. We have been doing Hypertufa and Sand-cast leaf workshops at Cypress Garden for about 15 years. The 2 day workshop is usually given in July or August. #hypertufa

Aggregates are generally peat moss, coco peat, and perlite or vermiculite. I do not like perlite because it is white. Perlite does not look natural to me but it will make a light weight pot. 
The peat moss or cocoa peat must be sifted through ¼ inch hardware cloth to remove lumps and sticks.

Hypertufa made with the classic proportions for mortar (1 part cement: 3 parts aggregate) has a composition of
·         3 parts Type I Portland cement
·         4 parts peat sifted
·         5 parts vermiculite or perlite
For pots 1 parts cement: 3 parts aggregate
For stepping stones & bird baths 1 parts cement: 2 parts aggregate
To increase strength, polymer fibers, liquid acrylic fortifier, and fiberglass fibers may be incorporated into the mixture. Add the fibers to a quart of water and mix thoroughly and add to the mix. 
 Other aggregate like sand, pebbles, sea glass and crushed oyster shells can be added though they increase the pots weight. Powdered or liquid concrete dyes can be added to the water first to tint the hypertufa to resemble natural rock. Buff, red and brown are the best colors to use. Fibers that protrude from the pot after it is finished can be burned off with a lighter.
How much water depends, less water or a dry mix will make a lightweight pot but it will need to cure longer or it will break easily. Shaking or vibrating the mold will make a heaver pot because the air has been forced out but it will be stronger.
Molds should be coated with oil for easy release. 
Old nursery pots make great molds. Duct tape the holes on the outside. You will  need  two pots, one larger than the other there must be at least 2  inches between the pots. The inside pot should be filled with wet sand to keep it from floating up. You might need to cut the pot the next day to get them out. 
 Cheap or broken foam coolers can be used but they must be reinforced with duct tape or they can split. Foam blocks cut with an electric knife can be used for the inside mold. 
Foam molds need to be cut to get the hypertufa out, but they can be duct taped back together and used again. 
Stepping stones can be made out the bottoms of 5 gallon buckets, Pizza boxes and heart shapes candy boxes  covered with plasticOr  made from 5/8 plywood and aluminum flashing attached with flat head screws. Use cookie cutters for patterns and enlarge the design. Minimum thickness is 3 inches. 
Hardware cloth and chicken wire can be sandwiched in between for reinforcement. Sea glass, broken pottery, tiles, marbles can be placed on the bottom or top of stones when molding.  Press them in deep or they will pop out later. Unmold the next day and bevel the edges with an old file or rasp so water can flow off the stone  freely.  Brush with a wire brush. Use an old nail or ice pick to dig around the pottery and other stuff. After the stone has cured, wash with vinegar to remove any cement film from glass, tiles and pottery. 

 Home made molds made with 5/8 plywood and aluminum flashing attached with flat head screws. Only about 1/2 of the mold needs to be unscrewed to take out stone. Just like taking a cake out of the pan. Use a 5 in-1 tool lift the stone off the board. 
You only need to remove about the flashing to get the stone out.Use the 5 in 1 tool to lift it out of the mold. 
Use a wire brush to clean the surface of the tufa this will help expose the peat and vermiculite . Brush the stones until smooth. If you not not brush it your pot will just look like a concrete pot. 

Use a drill to make the hole in the bottom of your pot.
use an old bit 

Drill the holes 1-3 days later, large pots may need more than 1 hole.

Foam coolers from the Dollar Store make great molds
 Add duct tape for support
 Inside block form covered with plastic and oil. weighted down with  sand or a brick or it will float up

 Feet were made with blocks of foam placed in the bottom of the cooler before tufa cement was added.
 ( this pot is upside down)


we made 2 batches to fill this mold the first pour was too wet and the second too dry.

finished pot
Edges were filed down  to give the pot an old worn look.

Adding Feet on the Bottom of your Pots

I like to add feet to the bottom of my pots. Feet help improve drainage by raising the pot up. Also I think they look look smart.  
I use wet sand to make these feet. This is called sand-casting
Make a raised cross shape in the bottom of your mold.
 shape tufa mix in a ball and add in the empty space between the sand 
add more tufa about 2 inches thick for the bottom of the pot

Next add a ring of tufa mix around the edge 
Add the inside pot, this should be weighted down with wet sand. This is important because the pot will float up as you add the tufa mix. Keep add the mix until you reach the top. 
Pick the pot up and drop it on the table a few times to settle the tufa mix.
 sand on the bottom also helps the mold come free more easily. Next step is to wash away the sand - usually the next day.

Decorating Your Pot

be sure to press the decoration in deep while the tufa mix is still damp, 

the fluting on this pot was from the fluted nursery pot used as a mold

After the pot has cured for a few weeks the decorations can be cleaned with vinegar to remove any cement film.

To make sea glass: add broken glass to a rock tumbler with a hand full of sand with water and tumble for about 3 days.