How to Make Concrete Molds From Plastic Items

Written by claire joy
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How to Make Concrete Molds From Plastic Items
Cheap plastic toys make good concrete moulds. (sand moulds in the snow image by Daria Miroshnikova from Fotolia.com)

What do you have kicking around the house that will make a nice mould? Making concrete moulds from plastic items requires you to think outside the box. Look in your shed or garage for common plastic items such as old tubs, flower planters, buckets, jars and large container lids. Plastic boxes, statuary, kids' beach toys, litter cans and sandbox toys are possibilities. With your collection of plastic moulds, you can create stepping stones, statuary, planters, personalised plaques and all sorts of decorations. Let your imagination guide you. Making concrete garden accents with plastic moulds can be thrifty fun for the whole family.

Skill level:
Easy

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Instructions

  1. 1

    Line a square, round or heart-shaped plastic pan with a tight layer of rocks. Carefully pour concrete into the mould to make a garden stepping stone.

    How to Make Concrete Molds From Plastic Items
    Jell-O moulds also work well for stepping stones. (Sun Face on Stepping Stone image by nTripp from Fotolia.com)
  2. 2

    Pour concrete into fancy, round or square plastic planters. Use a smaller plastic container to form the inside of the planter. Your new concrete planter will be shaped and decorated just like the hard plastic original.

    How to Make Concrete Molds From Plastic Items
    Planters like these are perfect. (planters image by Paula Gent from Fotolia.com)
  3. 3

    Pour concrete into a small round dustbin. Pour concrete into a plastic bowl and when dry, stack the cap on top to make a mushroom. Embellish with tiles, glass, pottery, rocks, pebbles, marbles, jewellery or trinkets of your choice using liquid nails.

    How to Make Concrete Molds From Plastic Items
    Don't pour the stem too thin. (mushroom image by Henryk Olszewski from Fotolia.com)
  4. 4

    Transform a flimsy old plastic birdbath into a solid concrete birdbath. Cut a hole in the top of the base and fill with concrete. Pour concrete into an appropriate sized plastic saucer; a smooth dustbin lid might work.

  5. 5

    Press an original plastic birdbath top firmly into the wet concrete with a slow twisting motion to form the bath basin. If desired, lift the top mould off again and lightly press fern leaves on top of the wet concrete to stamp it.

    How to Make Concrete Molds From Plastic Items
    Concrete needs to be at least 2 inches thick to be durable. (squirrel bath image by Ray Kasprzak from Fotolia.com)
  6. 6

    Replace the plastic birdbath top if needed to maintain the basin's shape. When dry, use a razor knife or sharp tool to cut along the seam of your plastic mould to release the birdbath base.

    How to Make Concrete Molds From Plastic Items
    Think big. (park fountain image by Aaron Kohr from Fotolia.com)
  7. 7

    Experiment with durable inflatable balls for children, basketballs, soccer balls or any other thick plastic ball. Cut a small hole, funnel in concrete until packed and overflowing, and then seal hole. When concrete is dry, cut away plastic and round out the top with sandpaper or a chisel.

    How to Make Concrete Molds From Plastic Items
    Don't expect your concrete spheres to be perfect circles using homemade moulds. (Concrete Sphere image by Richard evans from Fotolia.com)
  8. 8

    Grow sheet moss on top of your concrete ball or decorate it to your liking. The bottom will have flattened from the weight of the concrete, so it will sit nicely on top of a homemade pillar.

    How to Make Concrete Molds From Plastic Items
    Rub a buttermilk/moss mixture on balls and keep shaded. (green moss image by Julia Chernikova from Fotolia.com)

Tips and warnings

  • It is highly important to tap your concrete-filled moulds lightly with a mallet and vibrate to settle the concrete and bring air bubbles to the surface for a smooth finish, especially with statues and balls.
  • Spray your plastic moulds with a thin layer of mould release, lubricating oil or mineral oil before pouring concrete. Allow to cure for three weeks before painting or decorating.
  • Shop at yard sales, flea markets, jumble sales or dollar stores for cheap plastic gnomes, birds, rabbits, squirrels, turtles, frogs, lions or other statuary. Keep in mind something such as a flamingo may not work, because a long neck would be too difficult to pour. Inspect closely because the entire inner surface must be smooth, hollow and uniform in order to make a good mould.
  • You may be able to reuse hard plastic statue moulds if you can secure the seams properly. For instance, if you want to reuse your plastic piggy bank mould after it has been cut open, pouring may be tricky with a two-part mould. Seems must be tightly secured to hold the shape.
  • Follow all directions on your concrete mix packaging and wear gloves and a mask when handling concrete. Usually, moulds should be removed 24 to 48 hours after pouring concrete. Reinforce concrete as directed. Allow three weeks to fully cure before painting or embellishing.

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