Sephaku Cement shows steps to create concrete rubber moulds to cast future concrete creations over and over again. It’s no surprise that craftsmen, creators and art or sculpture enthusiasts are making use of concrete more and more to create concrete décor, statues and arty ornaments. Once having mastered the basics of creating concrete forms using single use plastic containers or ice trays and other precast moulds, you may just be ready to take your concrete creations one step further. With your favourite form in hands, from an ornament, vase, pot, bowl or sculpture see how to create rubber moulds to be used to create your next concrete masterpiece, on repeat.

To create a durable rubber mould to create concrete designs you will need:

  • Sealing Agent
  • Leak-Proof Container
  • Release Agent (that works on latex)
  • Pourable Mould Rubber
  • Razor Blade 
  • Step One:
    With the desired model item in hand, seal the surface of the item with the sealing agent, coating the surface with two layers of sealant. Be sure to allow each layer of sealant to dry between coats which will make sure that the models form is not manipulated by the layers of sealant. Haste is not on your side with this step whereby applying one thick layer of sealant will create bubbles and run lines influencing the shape of the original mould. Rather apply two thin layers taking time and having patience to ensure an accurate replica is created. 
  • Step Two:Using a leak proof container (plastic is usually your best bet) such as an old Tupperware, bucket or bowl, with the same sealing agent, seal the surface of the container.
  • Step Three:
    Follow this step by applying a release agent to the sides of the container as well as the model mould. The release agent needs to work on latex and polysulphide materials for best results and will assist with releasing the rubber mould from both the container as well as the model item.
  • Step Four:
    Typically made up of a powder and a liquid agent, using a disposable container, mix up the pourable mould rubber by adding the powder and liquid together. Ensure that the mixture is blended well with slow and steady mixing (rigorous mixing may result in air bubbles which will influence the smoothness of the mould). 
  • Step Five:
    Pour a few centimetres of the rubber mix into the “host container” to form a base for the model item to sit on without touching the bottom of the container. Wait a few moments for the base rubber to set slightly, forming a skin on the surface. Place the item to be cast onto the rubber base, gently pressing it down but not allowing it to touch the bottom of the container. Once placed in the centre, pour the remaining rubber mix around the item to be cast covering it completely in the rubber mix.
  • Step Six:
    Having allowed the rubber mould to set for a minimum of 24 hours, it’s time to remove the rubber from the host container as well as the item cast to reveal the concrete mould. Slide the rubber “block”, still containing the cast item from the “host container”. Using a razor blade or scalpel like knife, with great care, cut the mould in half creating two parts to the mould. Gently remove the cast item to reveal the perfect rubber mould to re-create duplicates of the original model item.This mould is perfectly suited to casting concrete décor and ornaments, making use of the original “host container when putting the two halves back together again.