The Stem Lamp

Being able to cut my own empty beer bottles I wished to build something which takes advantage of that nice warm glass colour. A lamp took shape in my brain...

To see a simple way to cut a glass bottle you can read my previous instructable here. Actually there are many methods and you can find a large number of tutorial here on Instructables.

For this project I used a big 66cl bottle and two smaller ones (33cl each). Of course you can choose any number or combination of sizes, and make a different design.

As light source you can choose between the old incandescent bulbs, or the more environmentally friendly CFL or LED lamps. There are pro and con for both types. The incandescent bulbs give a vintage look to the lamp in my opinion, but consume more energy and the become very hot, which may not be good since glass is not tempered. CFL and LED are a bit more expensive and although you can choose a warm light, in my opinion they miss the warmth of a flame .

You need three sockets too, and it's better looking for E14 lamps and sockets, which are smaller than E27 and fit well in the bottle neck. As wall plug cable I chose a gold one, with switch already connected, I use to keep some of them, different colours, since they are very cheap and useful in many projects.

My design considers three "stems" with different heights and placed on the base at the vertices of an equilateral triangle. To add a remarkable weight to the base I decided to build it with concrete, both to experiment a concrete design, and to obtain a vintage look. A plastic bowl like this costs about 2$, cheap enough to be destroyed with no scrupulosity.

The aluminium pipes used as stems are sold here in pieces of 1 m each. You can cut one piece in two parts of 35 and 65 cm, as you see in the schematic. Leave another piece 1 meter long. If you want a taller lamp you can buy three bars 2 meters long, and cut two of them at 135 and 165 cm. The bowl is big enough for a 2 m lamp too. Another design could be cutting a 2 m bar in 160 + 40 cm, and adding the 40 cm piece to the third 2 m tube, so to have a very tall lamp (160, 200, 240 cm).

To connect the stems to the base and to the bulb sockets I've used two different sizes of threaded iron tubes.

The bigger ones are a bit more expensive, they fit exactly inside the aluminium stems, and you need about one meter of them (for a three stems lamp). Cut the one meter bar in three equal parts (about 33 cm each).

The smaller ones have a thread which fits the bulb sockets. You need three pieces about 6-8 cm long.

Since the socket's thread is a bit small compared to the stems' inner diameter, we need to wrap up the 6-8 cm bars with a tape. Test the number of turns you need to make some friction between the tubes. I then secured the electric tape with a more sticky tape.

You need to wrap tape in two positions for every bar, like in the picture. Leave enough thread at one extremity to screw in the bulb sockets. Then connect wires and place the piece together.

To keep the bottles up I decided to go for a very simple and ingenuous way. Just cut three rubber bands from a thin bike tube. Put a band on the stem top extremity (maybe you want to extract wires and sockets for now), then flip over the external edge of the band, so that it will assume the shape in the picture. Now you can insert stem, wire and socket in the bottle neck, then pushing on the rubber band and pulling the wire you can lock the bottle in position.

Let's focus on the base now. To place the three holes look the schematic, if you don't have a goniometer you can simply measure the distances between holes and check that they are centered on the base.

The hole diameter has to be very tight around the threaded bars, since we have to fill the bowl with liquid concrete which otherwise would come out from the splits. Furthermore, the bars would act as supports for the full (and heavy) bowl.

This plastic cylindrical container will create a cavity on the bottom of the concrete base, where there will be enough space for wire connections, and maybe a future controller for light colours.

The straw is there to form a cut between cavity and external edge, where the power cable will pass through. Close the straw extremity with wet paper or something gummy.

The ~33 cm long threaded bars have to be screwed in the holes. To make the operation faster you can use a drill or an electric screwdriver. Screw them in until they protrude inside the bowl about 5-6 cm, then check closely that the inner lengths of the tubes are all exactly the same.

I also shaped two cardboard sheets with the three holes, so that they will help to keep the legs exactly vertical.

Now you can add a thin layer of silicone grease all over the inner surface of the bowl, this will help to remove the plastic from the consolidated base.

To reinforce a bit the base I added a metal thin bar folded in a big spiral. If you want to make something more effective you can build a cage about 2 or 3 cm smaller than the bowl. Wrap the wires extremities around the adjacent cage elements, then add some pins to keep the cage 2.5 cm lifted in the bowl.

I also filled the holes of the pipes with pressed paper, so that the concrete will not pass through, and I will be able to remove them pushing from inside the pipes.

Pour the cement with the sands, in a proportion of about one part of cement and three or four parts of sand, add water and blend continuously. Pay attention to not exceed with water, you can realize it when the mixture becomes suddenly too much fluid. If that happens simply add a spoon of cement and keep on blending. When the mixing has the right consistency (like what?... polenta?) you can pour it into the bowl.

To keep the bowl stable I suggest you to place it against two cornered walls, and to add something heavy on the free side. Check that all three legs are exactly vertical.

Place the smaller container on the bars centered in the bowl, then fill it with water, so that water weight will keep it down. The straw should be in contact with the bowl's edge.

The concrete will reach 90% of its strength after 28 days, but I think that paying attention you can extract the base from its mold after 2 weeks. You also have to open the holes to let the wire pass through. Push from the open extremity of the bars or dig a bit in the concrete.

Extracting the base from the mold is a bit hard. I decided to put it in the owen at 140°C for about 10 minutes. That made the plastic softer and allowed me to remove it with not much effort.

I painted the base in black, but you can also keep the concrete in view. The three little rubber o-rings are to thread onto the threaded bars, so that the aluminium stems will not ruin the base surface.

Then add some adhesive tape as thickness on the threaded bars, so that the stems will fit with a bit resistance.

I locked all three cables together with a cable tie, so that they keep everything joined.

Connect all three pairs of wires so that you have only two contacts (one colour each) to connect to the wall plug line.

I glued the concrete base to a wood plate, treated with shellac. I wished to make the disc a bit wider than the concrete base, but I probably exaggerated with sanding, and the diameters are identical. the consequence is that the concrete edge is very exposed to collisions, and it ruins very easy. So I glued a tape all around the circumference to cover any imperfection.

It's time to turn your lamp on and relax with the warm atmosphere :-)