Tutorial on making a Large Hypertufa Planter By Bill Aronson – Wolf Mountain Farm Copyright 2012 all rights reserved. Do not reproduce without written permission.
Hypertufa is the name given to an assortment of aggregate materials, bonded together with Portland Cement. They are used to construct or mold planters and many other items. Tufa was a type of porous rock used to make feed & water troughs decades ago. Those old troughs were discovered by Succulent Plant enthusiasts as great planters that held up for decades. Hypertufa can be made from several different materials. There are some basic steps to follow that make the planter strong and give it longevity. I will try to illustrate those basic steps but other than that, just have Fun making your pot. One note before we get started, Hypertufa must be cured if it is to have longevity. You must have the patience to cure your creations for 14 to 28 days. I have heard it said that each day of cure translates into another year or two of longevity. There are many different formulas for mixing Hypertufa. In this project I used equal portions (by volume) of the following: 1 part Portland Cement 1 part Sphagnum Peat Moss 1 part Perlite 1 part Sand Most of the formulas are basically one part Portland cement with three parts aggregates. You could change the above formula and substitute vermiculite for the Perlite. You could also substitute gravel for Perlite but that will increase the weight of the finished item. You could also make the item lighter by substituting another ½ part Sphagnum and ½ part Perlite for the sand. Other additives may include polymer fiber, acrylic liquid or fiberglass fiber to strengthen the item. I do not recommend fiber unless you are using a concrete mixer. Some people also add dye in liquid or powder form to create a faux rock appearance. If you can find white Portland cement you can better control the color of your item, unless you are shooting for grey. Please remember when you gather your materials you want Portland cement, NOT Concrete. Concrete contains Portland cement because that’s what holds it together just like Hypertufa. Concrete comes with it’s own aggregates, sand and gravel and generally has less Portland in it than Hypertufa. You could say Hypertufa is concrete with different aggregates.
There are several ways to make or mold your container. In this project I used two containers nested. The outer container or bowl to mold the outside of my bowl and another container or bowl forced into the mixture to create the inside of the container. This is more of a “poured” piece and mold. A simple way to make a Hypertufa Pot is to mix your mud more dry and stiff. Stiff mud can be put into a mold by hand and will stand up enough to create your inside space without another mold. If you are making your first attempt, mixing a small batch and using a milk carton or stiff shoe box or such for a mold, is probably a good idea. A stiff cardboard box lined with thin plastic (to prevent sticking) makes a good mold. Metal makes a bad mold that does not release well. If your mold (like mine) is plastic then a spray oil (mold release) will help to get the mold off. If you do not use a spray oil you may destroy your mold getting it off. Here we go… Step 1. Gather your aggregate materials and your mold materials. Step 2. Mixing - I put my materials into a large wheelbarrow for mixing. For This project I used one 3 gallon bucket full of each of the four ingredients. So when I was done adding them I had about 12 gallons of dry material.
I dry mix everything before adding any water.
A hoe makes a good mixing device. This large one with holes in it is called a masonry hoe. When you add the water be very careful to not add too much too fast. You do not want runny mud! Add a little water and start mixing.
Since I was shooting for the faux granite look I added black liquid dye to my mix so it would be dark with white flecks (the perlite). The peat and the sand also affect the final color.
Step 3. Pour your mold. I used a large plastic bowl (about 24� diameter). You must spray the mold down with an oil lubricant for mold release. A DIY veggie oil, a lubricating oil or cooking oil spray all work.
I decided since this bowl was so large I would use a wire frame in it to add strength. I already had some old wire frames for moss baskets laying around and it fit, so I used one of them. You can also use wire or fencing to make a wire frame. If some day your container cracks it will still stay together with the wire in it. I do not use wire on small pots, but add acrylic liquid on them. I put some of the mud in the bottom of the mold and then place my wire frame in it making sure it will fit and not stick out of the casting. Use a pliers to bend or adjust your frame too fit. This one was a little too tall so I bent the top over a little. Hypertufa should be three inches thick if you want it to last. The wire should not be too near any surface or problems may develop. Then finish filling the mold with mud leaving some room for the inner mold.
Step 4. Put your inner mold piece in place. I used another large nursery bowl (about 14� diameter). The inside container will try to float up out of the mud so you will have to have something heavy to hold it down, like a bucket of sand or gravel. I used a homemade steel anvil made from a piece of railroad track. I first covered the bowl with a piece of 1/2� plywood to spread the weight out and then added the weight on top. I used a paint scraper to smooth out the top of the mud.
Step 5. Now you must leave the mud to harden. I leave the thing alone for 24 hours. If you move it or mess with it can cause cracks and chips. After 24 hours I pull the inner mold out. I then take my paint scraper and knock of any pointy edges and smooth the top up. It is better to put a rounded edge on things to minimize chips.
You can drill holes later when it is hard but it is easier to do it when soft. I use an old auger bit I got at a garage sale for a buck. I just twist it by hand and remove the mud material.
Now I wait another 12 to 18 hours before I try to get the outer mold off. I will need to flip this very large and heavy piece so I prepare the top first. As I said before I am trying for faux granite so I want the white perlite flecks to
show through the dark material so I scrape the surface. The material is still easy to carve on or scrape. You can use a scraper or chisel or a wire brush.
A large project like this requires two people to flip the mold. I put a piece of plywood over the bowl and then flipped them both together. This prevents jarring and chipping. Then just lift off the outer mold.
Now you have your piece out and need to look it over for chips or defects, You can take some of the material scrapped of the top (powder), remoisten it and patch up defects.
Let the piece harden after patching for about 4 to 6 hours. After the patches hardened up I used my scraper to rough up the outside just like I did on the top. You can leave it with the smooth look if you prefer. I also cleaned out the drain holes as they had a little mud hardened in the bottom. It pushes right out with a piece of rebar or a screwdriver. Now your bowl is ready for curing.
For curing I put the bowl in the shade, wet it down and cover it with plastic. I uncover and re-wet it about every 5 days. The slower it dries, the harder it gets and longer it lasts.
After 24 days I uncovered the pot and flushed it out a couple times a day with clear water to remove any excess lime or chemicals. Then I planted it up with a bunch of Succulents. These should last about 40 years if done well. Remember if you plan to leave it outside forever you need to use Hardy Succulents or replant every spring. Good Luck and have fun!!