Recycled Glass Countertops

FOUR: CASTING

Casting a recycled glass terrazzo mix is very similar to casting ordinary concrete with one notable exception – the aggregate is really sharp. The crushed glass will tear through thin latex gloves so for this casting we’ll use  heavy duty rubber gloves for protection.

Step 1 – Pour Concrete

  • Your casting table should be indoors so your countertop can cure away from direct sunlight.
  • Turn vibrator on to a relatively high speed to help the recycled glass terrazzo mix flow.
  • Using a bucket, transfer the terrazzo concrete mixture from tub to form, bucket by bucket, until all the mix is in the form.
  • Spread the mix and push it into the corners with gloved hands or a trowel.
  • The form should be filled completely and evenly.

Step 2 – Vibrate and Trowel

  • If you’ve over filled the form, screed the excess concrete off the casting with a clean, straight edge of wood or steel. Work the board diagonally across the surface of the concrete in a sawing motion being careful not to disturb the foam walls or wall liners.
  • Once the terrazzo mixture is level with the top of the form and no more concrete is required to fill the form, turn the vibrator to a low setting.

Step 3 – Compact Mix

  • Allow the vibrators to run for roughly 8 minutes while all trapped air is driven from the terrazzo mixture. This will help reduce the number of air bubbles in the recycled glass countertop section.
  • Tamp around the edges with a trowel to help compress the glass into unfilled corners and drive any air that might be trapped along the edges of the form.

Step 4 – Cover and Cure

  • Tent the form with a thin covering of plastic to create a humid environment. Do not cure in the sun.
  • For this project we allowed the countertop section to cure for approximately 24 hours. Our shop temperatures dropped to 68ºF over night and the highs were around 75ºF.
  • Once the countertop section is fully cured, take some time to grind off any high spots or rough areas. This will save time during installation.
Previous: Mixing

No need for a large drum style concrete mixer for this project. A 1/2″ drill motor,  equipped with a good paddle mixer, is all that’s required.

Next: Grinding

Use a grinder to level any high spots or aggregate that protrude above the form walls. This is also when we ease the sharp edges along the underside.