For this project I wanted to capture motion in a stationary object. I wanted this to look authentic and organic but still have control over the overall shape. For this reason I used a fabric form in a very controlled way. That way I could let the properties of the fabric show through the cast but also control the shape of the pour. Making this a lamp really emphasizes the shadows, color and texture of the cast.
What you will need:
1.) A small tarp for the form
2.) Plywood and hardboard for the form base
3.) Rapidset Cement All casting grout
4.) Angle Grinder with sanding disc
5.) Drill with masonry and spiral bits
6.) Light socket with switch attached
7.) Length of lamp cord
8.) Paint can
9.) Spray filler primer
10.) Spray paint with color of your choice
11.) Spray Lacquer
12.) Cork for the base
Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.
Step 1: Making the Form
This shape is very organic so the only way to accomplish this is through fabric forms. I wanted to let the form introduce an organic nature while still giving me control over the angle, height, and width of the base.
1.) Find a piece of plywood for a backer to the form. Attach to smaller piece of plywood parallel to each other on the backer.
2.) Cut a piece of thin plywood or hardboard to the width of the backer. Now cut it to a length that can easily be bent into an arch between the two small pieces of plywood. This arched piece will serve to hold the back of the fabric and give the base a specific angle.
3.) I bought tarp at the dollar store as my fabric mold. It was more than strong enough for this application and was only a dollar which is good because it was going to get wrecked in the end anyway. Fold the tarp like the paper around a bouquet of flowers. Fold the point up a little to avoid any leaks in the mold. Attach the tarp the plywood using screws making sure there are now open flaps.
This will make a nice pocket that will create a specific shape based on the form's length and supporting arch but at the same time will give the grout a fluid appearance with the texture and wrinkles introduced.
Step 2: Casting the Base
What I chose to use for this cast was Rapidset Cement All. This is a high strength industrial grout mix perfect for detailed casts. Regular concrete may work just as well but I was concerned about the aggregate in the smaller parts of the mold. If you were to attempt to do this with concrete, go through the mix and remove some of the larger stones from the aggregate.
1.) Mix to a consistency that is good for pouring but not so thin that it will leak out of the mold. Take your time mixing to ensure that it is evenly mixed. I used about half of a bucket's worth of grout.
2.) I clamped the mold to a ladder before I poured into it. You have a very short amount of working time once you stop mixing so pour right away. Tap the mold to help it settle and level out the top of the mold. It will set up remarkably quick, so cover it right away to keep it from curing too quickly and cracking. Usually I would let this sit for about 8 hours but since there was so much I let it set up for about 24 hours.
3.) Remove the screws and/or cut the tarp and pull the lamp base out of the mold
Step 3: Making the "Splat"
So far the form of the base looks pleasing but is lacking authenticity in its relationship to the tabletop. Cement All has a bonding agent already in it that lets you pour right up against another cast piece without worrying about any bonding additives.
1.) I liked how the arch came out but the over all shape looked too vertical. To fix this I cut a triangular piece of insulation foam to prop the shape up.
2.) Mix some grout to a thick consistency so that it can be packed into the space around the foam piece. Smooth this against the rest of the base with a trowel.
3.) Add a little more water to the mix to make a more fluid mixture. Pour this around the base to create the "splat" look. Pouring this directly onto the tarp will make a more unpredictable organic form that will sell the "pouring" look.
4.) Smooth everything together with a trowel. Come back with a sponge to soften the edge between cast pieces.
5.) After it is all dry, smooth everything out with an angle grinder and sanding disc.
Step 4: Drilling the Hole for the Cord
In order to let the lamp hide the cord as much as I could, I put a hole in the base to run the cord.
1.) Grind a small flat spot on the base to help get the drill bit started
2.) Start with a small masonry bit for more control of position and angle.
3.) Switch to a larger and longer masonry bit to finish drilling all the way through.
Unfortunately, I ended up with a lot of vibration because my bit had a slit curve in it. It got stuck and I broke the base into 3 pieces. I used this to my advantage and drilled the rest of the way through easily into the hollow space where the foam was. I then cleaned up the hole with a chisel to make sure the cord could easily go through. I used Gorilla glue to put it back together. I clamped it for an hour and sanded it and it was good as new. I had bought some thin tubing to put into the initial casting of the base but thought I would have too much trouble keeping it at the right angle. If I were to try this again I would probably give the tubing a try.
Step 5: Painting the Lamp
Cement All cures very quickly so it can be painted almost right away. With regular concrete you would have to wait at least a week for it to cure enough to be painted.
1.) Use a filler primer to cover up any imperfections in the cast base. This will remove the texture of the tarp and smooth out the line between the two casts
2.) Pick a color spray paint and spray a few coats over the primer. Immediately follow this with at least 3 coats of lacquer, each a few minutes apart. This will seal everything and give the paint more durability. Let this cure for 24 hours.
3.) Take the paint can and give it a few bursts of paint to give it a messy look and seal it with lacquer.
Step 6: Attaching the Switch
When the painted can is dry, you can drill the hole for the switch. I bought a socket at the hardware store that has the switch attached at the back.
1.) Use a center punch to mark where you want the drill bit to start. Use a small bit first to get it in the right spot and then come back with a larger bit just big enough to fit the switch through.
2.) Take the nut off the threaded rod on the switch, put the switch through the back of the bucket, and reattach the nut.
Step 7: Attaching the Can
I thought attaching the can would be the hardest part but it turned to be very simple and strong.
1.) Take a scrap piece of wood and trace the curve of the paint can onto it. Cut this piece out on the band saw or with a jigsaw. Take the opposite side of same piece of wood and find the appropriate contour that fits against the back of the cast base. Cut this out on the band saw as well. Use the first piece of wood as a pattern to cut out two more of these pieces of wood.
2.) Glue and clamp these three pieces of wood together. When the three pieces are dry, sand them smooth.
3.) Glue the wood block to the cast base and let it cure. The best kind of glue to use for this is construction adhesive because it bonds well to all construction materials but will also fill in gaps well. Regular Gorilla glue does poorly with gaps. I added an extra piece of wood to tip the bucket back a little more.
4.) Drill two holes into the paint can so two screws can hold the bucket in place. You can mark where the holes are located on the bucket by spraying a little paint onto the piece of wood and placing the bucket against it. Remove the burrs on the steel with a countersink bit.
5.) Add glue to the wood piece and a lot of glue into the rim of the can. Put the bucket in place and drive the screws through the bucket and into the wood piece. Let this cure for 24 hours.
I added a few extra bursts of spray paint to hide the screws at the back of the can and sealed it with lacquer.
Step 8: Cutting the Cork Bottom
You don't want the base of the lamp to scratch up whatever it is sitting on. A sheet of cork solved that problem.
1.) Put down the sheet of cork. Place the lamp on top of the cork and trace the base.
2.) Cut out the cork piece with a sharp knife. Stay about an eighth inch away from the line on the inside to make sure the cork isn't too close to the outside edge of the lamp base.
3.) Attach the cork with high strength spray adhesive.
4.) Go back and remove the cork from the hollow spot in the cast where the foam was and where the cord will come through.
Step 9: Running the Cord
Run the cord through the base to attach it to the socket. You can take the socket right out of the bucket to attach the wire and easily put it back in. Put a light bulb in the socket and see how it works. I am really happy with the way that this build came out. I love the way it looks on my desk and especially the color that I chose. I learned a lot from this and I hope that you did as well!
Participated in the
Lamps and Lighting Contest 2016