Concrete Casting

Lesson: Concrete Casting

Concrete has a very thick consistency when casting- it is unsuitable for delicate thin pieces.

·         Spray your mold with mold release.

·         Scoop some concrete powder into a cup.

·         Add any additives such as vermiculite or sand- do not add more than 10-20% of the amount of concrete.

·         Add water slowly as you mix.

o   You want the mix to be as dry as possible and able to fill your mold. Think of ricotta cheese consistency. If the mix is too wet, add more concrete. Too dry, add more water.

·         Add any powdered color and mix well.

o   Concrete doesn’t color as deeply as the other materials. It will tint the concrete rather than truly coloring it.

o   For brighter colors you can purchase concrete stains that you pain over the surface after curing.

·         Spoon/pour the concrete into your mold.

·         Let cure for 4-6 hours then cover in plastic wrap.

·         Let cure for 1-2 days.

·         Demold and do any prelimanry wet sanding.

·         Wrap in damp paper towels and put in to a ziploc bag.

·         Keep the paper towel damp, and let cure for another 5-7 days.

·         Remove from damp paper towel and finish wet sanding.

·         Let surface dry.

Working with the castings:

Adding metal frames or armatures can increase the strength of the concrete.

Rather than drilling the concrete- consider embedding tubing in the casting. You can drill concrete but you need special bits and it is time consuming.