Making a Hypertufa Planter
First I want to say that I am not an overly experienced hypertufa maker. I had never even heard of it
until July 2007. I got interested and surfed around the net gathering as much info as possible. I just
dove fearlessly in and made several big mistakes on my first try (like trying to build a
large 16"x22"x8" trough on the first try, not too smart!). If your really interested but a bit
hesitant to try it, my advice is just do it. Start with something real small like a few small bowls. You may not want
to invest in a lot of materials to find you don't like doing it later. If you can borrow some cement, that is better because it usually
comes in 94 pound bags for about $9. I know I've made at least one mistake on every single project I've done, yet none were fatal.
The idea with hypertufa is to use a cement based mixture to mimic rock. Peat moss is the main ingredient in hypertufa that
gives it the 'look'. If you don't use peat moss your not making hypertufa.
Additional benefits of using peat and perlite in a cement mix is that it makes the whole thing "airy" and it will act
more like a clay pot. As we know this is good news for cactus & succulents - especially if you live in a wet climate.
Here is some of my finished handiwork from last year:
A 16x22x7 inch trough with common succulents
A smaller 10x15x6 inch trough with hardy cactus
A small 6 inch bowl with a young Echinocereus
List of items used
portland cement - I buy Quikrete brand 94 lb bag, not sure if you can get a smaller bag
sand - I use quikrete all-purpose sand. sand is optional, see below. Your town may offer free sand but I find ours unusable as its dirty, full of weeds and whatnot.
sifted peat moss - I buy whatever is cheapest. I sift the twigs and other larger pieces out of the peat moss using a screen.
perlite - whatevers cheapest, vermiculite is an alternative.
water - its free from your faucet
Other important items used:
large heavy duty rubber gloves - should cover up close to elbows
goggles - you may not want cement/sand/perlite dust going in your eyes
dust mask - you don't want to breathe cement/sand/perlite dust (don't fret, once you start adding water to your mix
the goggles/mask can come off)
apron/ junk clothes - it can get messy so put the good clothes away.
mixing tub - you need something to mix your hypertufa in. A wheel barrel will work. I bought a plastic mixing tub from a
local company, I later saw the very same one at Home Depot and Lowes for less. Hey, if you already have, can borrow or can
afford to buy a motorized cement mixer then that will make the mixing part much easier!!
measuring bucket - I work in US dry gallons and use a 1 gallon bucket to measure each item. Use whatever unit of volume
you like and you can use a site like www.onlineconversion.com
to convert units
spray bottle - fill this with water and keep it handy
mold - you need something to shape your mix, I'll get into that more later.
plastic drop cloths - If you want your work area clean lay down a large sheet of plastic. Also I use this same plastic to
cover my molds which makes removing the mold from the hardened hypertufa much easier.
wire brush & cement tools - you need to "touch up" your hypertufa's imperfections like smoothing out edges
before it permanently dries. More on this later
wooden dowels - I use these to make the drain holes
work area - for mixing the dry ingredients you need to work outside so those nasty dust particles float away.
Once the mix is wet you can move it into a garage or work shed if you want.
warm weather - I've read that cement doesn't cure as well when temperatures are below 50 F (10 C). Best to do this
in warmer late spring/summer weather.
Making your mold
Your mold is what you use to determine the shape of your planter. There are a million ways to make molds and there is no
right or wrong way as long as it works. Look around the internet, I've seen lots of genius ways to make molds, the sky
is the limit. I prefer to mold on the outside of something (like a bowl, a box etc..), this way you get an uneven more
"natural" look on the outside of the planter. Hypertufa won't stick to plastic so I cover all my molds with
plastic drop cloths and tape it down all loose edges or folds in the plastic. Even if using a plastic pot or tub, like
my current project, I still cover it in the plastic sheets cause I found that slapping hypertufa mix on a perfectly
smooth surface can create a vacuum and might be forced to cut the plastic up to get your mold out. Another method
is a box inside a box with spacing around all sides of inner box, the hypertufa mix is filled into the spacing.
Have your mold ready to go at least the day before you start as this part alone can take some time.
My mold for this project
Here I am going to make a trough out of a standard dishpan. I'm going to turn it upside down and put the hypertufa on the outside.
I then tape plastic sheets all over the pan and make sure all loose edges are taped down.
Next I lay down a large plastic sheet in the area I'm going to use for covering the mold. I used a smaller sheet and draw
a line around the tub to use as a guide to get the right thickness.
My mold is now ready to go.
I forgot to take a picture but I also made 4 wooden dowels about 1/2" thick and 4" long. I covered these with
saran wrap and tape it smooth. I also draw a line about two inches from an end. When I put them into the mix on top of
my upside down dishpan the line will help me get the thickness of the mix applied right. If you don't want to work with dowels
you can drill drain holes into your trough after it has completely dried.
The formula I personally use is:
1 part - portland cement
1 part - sand
1 part - sifted peat moss
1 part - perlite
I live in a climate where it can easily get below 0F (-18 C) and can stay below the freezing mark for weeks at a
time. Because of this climate I add sand to my hypertufa mix for added strength. If you live in a warmer
climate that doesn't see much freezing weather then you can skip the sand if you want and use:
1 part - portland cement
1 1/2 part - sifted peat moss
1 1/2 part - perlite
This will be lighter because sand is heavy, peat moss is lighter and perlite is very light. There are a lot of other
formulas floating around the net. I believe it has to have peat moss to be considered hypertufa.
Reinforcement fibers (optional)
I bought a bag of reinforcement fibers for cement from a local cement supply company. They are supposed to add strength
to your cement mix. I really don't know much about it but I add a pinch or two to my mix while its still dry.
These fibers can be a small pain to break up and mix in plus they'll float away in the wind if your not
carefull. A small bag should cost $5-$10.
How much material do you need?
This is a tough one. It will obviously depend on the size of your item and how thick you want the walls to be.
If you know the volume that your material needs to fill up then there is a way to approximate the total materials
needed. If your mold is an odd shape or is free form then you kinda have to guess based on experience. Hint: try
something small and easy for your first few attempts then you'll start to get better at guessing for how much you need.
For this project I'm using a standard size dishpan here in the US. the size is 13.5x11.5x5.25 inches
(34.3x29.2x13.3 centimeters). Since I want to play it safe by having a bit more material than necessary I'm going to
bump it up to 14x12x5.5 inches (35.6x30.5x14 centimeters). I will be molding the hypertufa around the dishpan
while its upside down.
The calculation of volume needed is a bit trickier than you might think. Unfortunately I can't do any fancy
computer graphics to illustrate what I'm calculating, so I may lose somebody here. Anyway here goes. I want my walls
and the bottom of my trough to be 2" (5cm) thick.
For calculation purposes the total height is going to be 5.5" + 2" = 7.5".
The total length of the longest side will be 14" + 4" = 18".
The total length of the shorter sides are 12" + 4" = 16"
The volume of the longest side is going to be 18" X 2" X 7.5" = 270 cubic inches. Multiply by 2 since
there are two long sides and you have 540 cubic inches.
The volume of the shorter sides is going to be 12" X 2" X 7.5" = 180, X 2 = 360 cubic inches. If you notice
I used twelve for the length and not 16 because there is overlap with the longer sides so that area was already calculated.
The volume of the bottom is 12" X 14" X 2" = 336 cubic inches, here I did not use 18 X 16 for the bottom since
each side calculation was a full 7.5" in height so the bottom area under the sides is already accounted for.
Now I have 540 + 360 + 336 = 1236 cubic inches. Ok, I'm not done. Now if I use 1 part each of my ingredients for exactly
1236 cu inches it is NOT going to work. The perlite and peat moss are airy so the cement and sand will work in between and
a lot of the materials will share the same volume space. So mixed together they won't equal 1236 cu inches. I forget where
but I found and online site that used a multiply factor of 1.65 to approximately account for this shared space. So multiply
1236 X 1.65 = 2039.4 cubic inches. I used this 1.65 factor twice last year and its pretty good. You still want to probably
mix a bit extra as having a little too much is no problem but having too little is a problem. And again once you do a few
of these you'll start to get the hang of guessing for material needed.
Now since I'm not sure know how to measure 2039.4 cubic inches I'll convert this to US dry gallons. which happens
to be 7.6 US dry gallons. I'm going to go ahead and bump that to 8 dry gallons. This should give well enough material
to mold onto the outside of the dishpan. I have a small bowl for a mold ready to go if I happen to have a lot of extra.
So ingredients used will be: 8 gallons divided by 4 parts = 2 dry gallons each item
2 dry gallons each of portland cement, sand, peat moss and perlite. This makes it real easy since I use a 1 gallon bucket
for measuring. So two bucketfuls each.
Time to mix
Now that I know how much stuff I need its time to start mixing. First I fill up a 5 gallon bucket about half full
with water, put it aside. I put on the rubber gloves, goggles and mask. I measure my 2 gallons of each item and dump
them in the mixing tub. I then toss in a healthy pinch of reinforcement fibers. You can put your tub on a table
if you don't want to bend down.
Here's peat moss, perlite and sand in the tub.
Now with portland cement on top.
I start mixing the stuff with my hands or a small hand shovel. Swirl it around and keep going until it looks evenly mixed.
Keep checking for pockets of hidden unmixed material on the bottom, they are hiding in there!! When you mix everything
turns grey like the cement. You are done when everything is an even grey color. I continue to mix for a few minutes
afterward just to be sure.
Mixing the dry ingredients
Here its now completely mixed
When I'm fully satisfied that its completely mixed I take the bucket of water and I poor approximately 1 gallon in. Work the
water around until its evenly mixed in, The mix should still be way too dry at this point. Take off the goggles and mask
(yeah!). Now keep adding in small amounts of water then mix it completely in before adding any more. You want to keep
doing this until the mix is the right consistency. Getting the consistency right isn't too hard but you want to be sure
its not too dry or too wet. The correct consistency is when you can scoop some up, squeeze it and a little bit of
water runs out between your fingers. You DO NOT want it wet to the point where it will poor out like a heavy liquid.
It should still hold shape when you squeeze it but be wet enough that a little bit of water dribbles out when squeezed.
There is no correct amount of water to use from project to project even if you do the same mold over and over. Humidity
and other factors will determine the water you need. Always add a little at a time as you get close to being correct
and again always fully mix the water in before adding more. If you should happen to put in too much water the only
thing you can do is to add some more dry ingredients until it gets back to normal.
Mixing the water in, its harder at first.
Splashing small amounts as you go.
Here the mix is "correct".
Putting the mix on your mold
Once you are satisfied that the hypertufa mix is the right consistency you need to immediately go to work by slapping it
onto your mold. I start by putting some along the bottom edge then put a layer on top. Then I stuff the dowels into
the mix on top where I want the drain holes. Now keep adding mix along the sides working your way up and once you have
enough to connect the top and bottom it should hold. Note: The mix may want to slide down on the side walls of the
mold, don't panic it happens all the time to me, as long as your mix isn't too wet you should get it to hold place.
If it ends up way uneven or really thin in areas, don't worry. Thick areas can be trimmed and you can ADD more
mix at a later date to even it up.
Applying to hypertufa mix onto the mold
Now about every 4-5 minutes you'll want to swirl all the mix around in your tub because this is cement after all and it will
start to harden up if left untouched for too long. Besides beginning to harden up the mix may begin to dry out especially
on a day with low humidity. Have your spray bottle handy and squirt a touch in if the mix seems to be getting dryer as
you go along. Ok, keep adding mix to the mold paying attention to the lines drawn around the mold and on the dowels.
Once you have completely covered adding the mix on gets easier and easier but you can lose sense of what spots need more
and what spots are done. That's way I draw lines as a guideline. You can also poke into it with a small pencil or something
if you are unsure of the thickness. As it gets more and more covered try to gently smooth out clumpy spots or tease some
of the edges to get rid of a split in the mix. It is all easier than it sounds (hehe).
The mix is now fully applied. It ended up a bit bottom heavy on me as the mix constantly wanted to slide down.
I may have to add some mix to the walls if it turns out too thin.
Once you have the hypertufa on the mold as planned (or close to it) now you cover the whole thing with a sheet or two of
plastic and put some items around the sheet to hold it in place and keep it as air tight as possible. Now you mist your
hypertufa 2,3,4 times a day, whatever your schedule allows. To do this, simply pull off the plastic, mist all over with
the spray bottle, then cover it back up. The idea here is to keep the hypertufa mix slightly moist so that it
hardens slowly. I'm not an expert on the subject but the chemical reaction of the cement and water forms a
stronger bond the longer it 'cures'.
Covered in plastic
Note: You must have patience at this point, do not rush. If you try to unmold too soon it will all probably fall apart.
Unmolding your hypertufa
After 2 to 4 days of daily mistings you'll need to get your mold out of the hardening hypertufa. The hypertufa is ready
to unmold when it feels hard but you can still put a groove in it when you scratch it with your finger nail. If it
feels at all soft wait 24 hours and check again. I was able to unmold a small bowl in just 30 hours once but one
of the larger pieces I made took close to 5 days before I felt safe handling it. You kinda just know when it
feels ready. Since I used dowels I remove them first. I find that most come out easily (if covered in plastic)
and others take some time to work out. Don't go crazy just take your time and slowly work them out by using
pliers. Once the dowels are out, Its time to flip the whole thing over. For this I put some old blankets or
other soft items down next to the trough and flip it (roll it over) onto them so it doesn't break. Get somebody
to help if its too heavy for you. The trough is still quite breakable at this point so handle gently! Now that
its right side up you can see the mold. Slowly work the mold out. Use a screwdriver or something and work gently
around the edges (like opening a paint can) keep going until it pops up enough to where it will almost jump
out on its own. This is where having a flexible mold is handy. The dishpan I used could be bent enough
to release trapped air and I was able to remove it no more than a minute.
My trough unmolded, it looks like a tub shaped chocolate bar. As you can see the drain holes aren't all the way through. There
is a very thin layer that formed underneath the dowels. I just poke right through with a screw driver.
Touching up imperfections
Now that the trough is out its mold its time to rough it up a bit. Get out the wire brush, cement file, screwdriver or any other
tool handy for the job. The first thing you'll notice is that some of the mix spreads out on the bottom causing
a lip to form around the whole edge. This easily flakes off with a file or wire brush. Inspect the shape of the
trough and see what areas are uneven or have unwanted blemishes. A thicker edge can be easily filed down now. A stray
stone from the sand may stick out as a sharp edge, file it down or chip it out. I personally like minor imperfections,
like a bit of unevenness or a somewhat lumpy look, as it adds character. If you want to round off edges do that now.
Another thing I do is work all over the entire trough with the wire brush, I want to get rid of that thin "chocolate"
layer that forms on areas especially where it touched the mold or floor. Just scrub an area until you expose some of the
perlite beneath. The whole outside parts that people will see should have a speckled with perlite look when done.
Close up of top edge after roughing it up some. Perlite specs are exposed and I can even see some of the reinforcement fibers
sticking out the side.
Side view of trough roughed up, this is how it will look only that it will get much lighter once it has completely dried.
I like to scour out the drain holes a bit; meaning I want to make sure that excess water will want to go down them. I take a
large flat screw driver and work around to top of the hole making it recessed compared to the rest of the bottom floor
of the trough. If for some reason the drain holes don't seem adequate you can always drill a few more in later after
the trough is fully cured and dried.
Close up of drain holes. There was some loose material inside the drain holes when I took the picture, the holes are really nice
and round about 1/2 inch (1.25 CM) wide.
After you are done with all the touch ups, mist all over and cover the trough back up under the plastic. I continue to mist
twice a day for another whole week at this point.
Misted and back under the plastic, this time right side up.
After the week of mistings the trough is moved outside left uncovered to dry out. Getting rained on is fine.
The portland cement contains lime which will begin to leach out of the trough when it gets rained on, if you don't
get rain you'll want to hose down the trough a couple times a day.
After about two weeks outside the trough will be cured and dry enough to plant in. The plants used and soil mix is up to you.
Now its time for you to have some messy fun!!
Author: Andrew Plona