Those nasty air bubbles !!
SO we pour our concrete into the mold and let it dry for the recommend 24 hours. The next day we come back on open up the mold only to find a pin and potholed disaster….WHAT HAPPENED !! ugh..sigh…disappointment.
So what can I do different next time to not have these?????
The MIX Firstly is the mix itself correct? It needs to be much wetter then the mix you used to pour you front step or back patio. The mix needs to just fall off the shovel or mixer blades. Should be very loose.
Release Agent A release agent creates a space between your mold and the concrete for the air to move. With the hints below the air will move to the top of the mold and out the top.
So you have poured the concrete into the mold now what ???Well how about … Vibrating, Prodding, Bumping or Tilting.
- Prodding the concrete mix in the mould with a rod or reinforcing rod many times gently, will help break water and air pockets and aid in the settling of the concrete mix.
- Use a Rubber Mallet and gently hit the side of the mould during and after pouring will greatly reduce the number of surface air holes and will help in filling undercuts.
- Depending on the shape of the mold it is sometimes necessary to tilt the mold as you fill it to ensure no undercuts. Continue filling your mold until your mold is slightly overfilled. This will help the water flow off your mix.
- Use a Vibrating Table by placing the empty mould on a vibrating table. Pour in some mix and switch on vibrator. Whilst vibrating continue to fill mould. Switch off and remove mould to cure. Over vibrating can cause extra wear on your mould and the mix to separate so keep to around 1 minute.
I hope these hints will help you get the beautiful sculptures from your molds!!