Fruitcake: a Translucent Terrazzo Floor Light




Introduction: Fruitcake: a Translucent Terrazzo Floor Light

Terrazzo is a beautiful and resilient composite material made of crushed aggregate such as glass, quartz or other stone, contained within a pourable binding agent, like concrete or other polymer, polished to a smooth surface finish and often used for flooring or walls.

For the designer in me (and so many others), the material is endlessly inspiring, and it's a fun design exercise to consider how to use the material in new and different applications. Through some experiments with crushed glass terrazzo aggregate samples given to me by a friend, and 2-part pourable resin plastic, I stumbled upon a luminous result: Fruitcake, a translucent terrazzo floor light!

For this Instructable, I'm going to walk you through some of my learnings (AKA, mistakes) in working with terrazzo and pourable plastics, and guide you through the process of creating your own Fruitcake.

Step 1: Assemble the Ingredients

You'll need to assemble the following tools and materials to create your own Fruitcake floor light. I've split the ingredients into three parts:

Molded light shade (the Fruitcake itself):

  • Another set of hands for the mold pouring process
  • Respirator and rubber gloves (for you and your helping hands)
  • IKEA 14" Blanda Blank metal salad bowl
  • IKEA 11" Blanda Blank metal salad bowl
  • Smooth-on 300 Series 2-Part Liquid Plastic (2 sets of the 16oz size)
  • Paint mixing bucket to prepare the 2-part plastic resin
  • Wooden stir stick
  • ~20 cups or equivalent volume of tumbled sea glass or other translucent light-emitting aggregate
  • Mold release spray
  • Drop cloth for any spillage
  • Stack of 12x12" boards or other ~10-20 pound weights (these will hold down the mold during the curing process)
  • Utility knife to trim off any flashing (leftover unwanted plastic remnants from the mold process)

Wooden Dowel Legs:

  • 1/4" round wooden dowel (10" or less total length needed)
  • Hand saw
  • Power drill
  • 1/4" drill bit
  • 5-minute epoxy
  • 100 and/or 220 grit sandpaper

Light fixture:

  • LED lightbulb 40W or whatever bulb desired
  • Porcelain lamp holder light socket with screw terminals
  • Power cord with stomp switch (though stomp switch can also be purchased separately and spliced onto the wire during this project).
  • Wire snips / wire strippers

Step 2: Early Experiments With Glass Aggregate and Pourable Resin

When a colleague of mine gave me a few promotional tackle boxes full of crushed glass aggregate samples, I was eager to start experimenting with my own funfetti terrazzo concoction. I purchased some Smooth-on 300 2-part pourable resin and selected my favorite colors from the sample collection. I mixed up the 2-part material (more on the process later) and then poured that and all my favorite colors of glass chunks into a small painters bucket. Shortly after, I had a terrazzo disk! Wasn't really sure what to do with it, but forged ahead.

Step 3: Early Experiments: the Terrazzo Bowl Fiasco

I decided it was time to try and make something functional. A lampshade came to mind. I grabbed two bowls, a larger glass mixing bowl, and a metal mixing bowl with a slightly smaller diameter, to make sure the terrazzo lamp shade would have enough wall thickness.

A friend had told me that mold release spray would be helpful for a project like this, so I purchased some and sprayed it onto the inner surface of the larger glass bowl, and the outer surface of the smaller metal bowl. I poured 2-part Smooth-on plastic resin and more colorful aggregate into the glass bowl, pressed the metal bowl inside and then waited for the resin to set.

After the resin had cured, the smaller metal bowl popped out easily. The outer glass bowl wasn't as agreeable. Even though I had used mold release, I had forgotten to factor in the brittle nature of the glass, and the new exoskeleton shell wouldn't budge! In a bowl-dropping moment inspired by Ai Wei Wei, I decided to drop the mold in hopes of a revelation, but I ended up with two halves of a broken Terrazzo bowl with a spider-cracked glass coating! It was a good reminder that in this situation, mold release spray couldn't help a mold that didn't have proper 'drafting' (easy to release angles) or flexibility.

Step 4: To Begin Your Fruitcake, Assemble Your Aggregate

Coat the inside of the large bowl, and the outside of the smaller bowl, with a healthy dose of mold release spray feel free to brush it on, or rub it on with a rag as well. This will be a helpful lubricant for releasing the Fruitcake from the mold.

Fill the large salad bowl about halfway up with tumbled sea glass or aggregate (approx. 15-20 cups of material, based on subtracting the volume of the smaller bowl from that of the larger one), so that when you push the smaller bowl into the center, the aggregate pushes up to about 1.5" below the surface of the large bowl. The goal is to have consistent thickness on all sides of the dome.

The size and density of the aggregate you use will determine how much liquid plastic resin you'll need to use to fill the negative space. The more negative space between the chunks of material, the more liquid you'll need to mix and pour into the mold.The liquid will fill the gaps, and even if it sets as a nearly opaque plastic, the glass will still transmit light.

Step 5: It's Time to Pour the Mold

It's time to put the salad bowl mold to use and pour the mold. This is where things start to get accelerate, so it would be helpful to invite a friend to help out for this phase.

While wearing a respirator and plastic gloves in a well-ventilated room, and using a wooden stir stick and plastic mixing bucket, stir up the 2-part pourable resin plastic based on the manufacturer's recommendations. Here's a video from Smooth-on, the plastics company that I used for this project. I ended up using 1.5 sets worth of 20 oz (or similar) cannisters of the 2-part resin to fill the space created between the walls of the small and large salad bowls.

Once you've mixed the resin, it's time to quickly pour the mold. While your friend presses the inner bowl down to spread the aggregate upward and ensure even wall thickness, pour the liquid plastic resin into the space between the inner wall and the outer wall of the two bowls. It's important to move quickly and pour evenly around the bowl to make sure there is even distribution of the plastic in the mold. Make sure to keep the plastic from getting on your skin or clothes, but be prepared for some spillage.

Step 6: Allow the Plastic to Set

Once you've poured the liquid plastic and pressed down the inner bowl to ensure an even thickness around the plastic dome, place a stack of boards, bricks or anything heavy onto the smaller bowl to keep it weighed down while the plastic cures. It's important to make sure the weight is small enough to be pressed down without being impeded by the wall of the larger bowl.

With the inner bowl weighed down, it's time to let the plastic set. It will start to heat up as it sets, so be careful of touching the bowl during the curing process. It only requires a few hours to set, but I'd give it 12 hours or so to make sure it's fully cured.

Step 7: Remove the Fruitcake From the Mold

After the resin has cured, it's time to remove the Fruitcake from the mold. With proper mold release spray, removing the Fruitcake should happen fairly easily. You may have to turn the larger bowl over and drop it a few inches onto the ground to make the Fruitcake budge.

Step 8: Drill and Install the Wooden Dowel Legs

With a utility knife, carefully trim off the excess material left from the mold process, called flashing. You can use the sand paper to smooth any edges, if they feel too sharp.

Now it's time to install the wooden dowel legs. Take your hand saw and cut 1/4" wooden dowel rod to three ~2" lengths (x3), marking the lengths with a ruler (measure twice cut once). Triangulate 3 equidistant spots on the flat surface of the wall of the Fruitcake lamp shade and drill 1/2" into the plastic. It will be much easier to drill into the molded plastic, so steer clear of the glass.

Mix the 5-minute epoxy by mixing equal parts and put a small dollop into each drilled hole. Then place each of the three dowels into the drilled holes, making sure they are pressed in the same distance (about 1/2") so the Fruitcake will stand evenly. Let the epoxy cure, and then turn over the Fruitcake to see that it stands level. Sand the bottom of the dowel(s) if you would like to tweak the gap between the Fruitcake and the ground.

Step 9: Assemble the Light Fixture

Take the power cable with stomp switch and use the wire snips (and trimmer if you have it) to connect the two cables to the light socket fixture. Use the screw driver to attach the wires by wrapping a wire around each screw on the bottom of the light socket fixture.

If you are attaching a stomp switch to the cable, you will need to split one of the individual wires halfway down the cable and pull them apart from the other wire so there's a bit of extra wire on either side of the split. Then disassemble the stomp switch, and splice the cable back together inside the switch itself.

Make sure the stomp switch and socket work by screwing the lightbulb in, plugging into the wall and stomping!

Step 10: Final Assembly

With the dowel legs cured, and the power cable and stomp switch working correctly, it's time to bring the Fruitcake to life. Find a power outlet near where you'd like the floor light to live (probably out of the way of foot traffic in your home or office), plug in the power cable, center the bulb beneath the Fruitcake, and stomp on the switch!

Step 11: Enjoy Your New Fruitcake!

Please reach out with any thoughts on improving or augmenting the Fruitcake recipe and feel free to share any evidence of your own Fruitcakes! Thanks for joining me on this journey.

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    3 years ago

    I love this. It's really neat. Thank you for sharing.