You don't need a pottery wheel or an expensive mold to make a serious concrete planter. This build uses a recycled plastic container as the form and three layers of cement cloth pressed against the inside. The pot comes out light enough to carry and tough enough to winter outside.
It follows Paradise Builders - Planter Skool, who refined the technique on big outdoor planters. Materials run about $20. Wear gloves and a dust mask, and give yourself two days before you demold.
What you need
- Cement cloth, also sold as cement fabric or concrete canvas
- Grey Portland cement, plus white Portland for the rim
- A plastic container in the shape you want
- Dish soap as a release agent
- Putty knife, bucket, gloves, dust mask
- A tire valve and a compressor for the demold
- Exterior concrete sealer
Is this the cement cloth method or a poured mold?
Cement cloth, and nothing here gets poured. You cut the fabric into squares, butter both faces with cement paste, and lay them against the inside of a soaped container the way a plaster cast goes on an arm. The container shapes the piece, it is not a cavity you fill, which is why the walls finish a quarter inch thick.
For the draped look, where the cloth hangs over an upturned bucket in folds, lay the soaked fabric over the outside of the form instead. A hypertufa planter is the other lightweight route.
Choosing the mix
Bagged concrete has gravel in it, and stones cannot pass through a fabric weave or sit in a quarter-inch wall. Plain Portland cement at a thick yogurt consistency soaks into the cloth and laminates one layer to the next. Craft mixes carry sand and a polymer for flex, which suits cast pots. Ratios are in how to mix concrete for crafts. White Portland earns its price on the rim, where it sets harder and finishes cleaner.
Curing, and why demolding early cracks it
Cement does not dry, it reacts. Water and cement grow crystals that knit the wall together, and most of the strength arrives in 48 hours. Pull it at six hours because the surface feels hard and you get a hairline crack up the side. Two days under loose plastic, which holds moisture against a wall that would otherwise dry chalky.
Cold slows it down. Under about 50F the reaction crawls, and below freezing it stops while the water in the wall expands. A planter built in an unheated garage in October wants three or four days.
Drainage holes and sealing
Drill the drainage hole, do not cast one. A masonry bit through the cured base, run slow with the hammer off, gives a clean hole. One does a small pot, three or four a big one. With no drainage, water sits against the roots and in the wall, and a hard freeze splits the pot.
Seal the outside once cured. These walls are thin and porous, so a penetrating sealer soaks in and stops water wicking through and blooming white efflorescence. Glossy topicals belong indoors. Sealing concrete crafts compares them.
Common mistakes
- Not enough soap. That film is all that stands between a clean release and an hour of prying.
- Air behind the first layer. Bubbles against the plastic become craters on the show face. Press each square out from the center; fixing air bubbles covers repairs.
- Seams stacked on each other. Stagger them so a weak line sits behind solid cloth in the next layer.
- Paste mixed too thin. Runny cement slides off and leaves the weave showing.
The technique scales up and down: a concrete hanging planter, a concrete bird bath, or a concrete pumpkin for the fall porch, all in crafts.
