Introduction: Cosmic Light With LEDs Embedded in Resin

About: Always making something....
I wanted to make a light out of resin that used LEDs but no soldering (I know a lot of people don't solder, and there are probably a few like me that can do it but don't really like to do it.) It's powered by a couple of coin batteries so it's easy to work on without any risk of shock. And the finished product is a glossy, atmospheric light with a soft glow.

All of the materials for this project can probably be found between a craft store, a home improvement store and a Radio Shack, but you can round a lot of it up for cheaper online. I got most of my supplies on ebay.

Personally, I made this because:

My bedroom has a light switch by the door.
My bed is not very close to that switch.
I have a lot of sharp metal sculptures in my bedroom, as well as a bed with unforgiving wooden corners.
I wanted something more special than an ordinary night light that could be used for the time between turning off the wall switch and making it safely into bed.
And it looks great between my Martian lunch box and little plastic dudes landing on the moon.....

*Apologies in advance for what appears to be incompetent photography - resin is very shiny and my camera lacks appreciation for reflective materials. It's also not that hot in the dark.

Step 1: Materials List

a rectangular resin mold
This used a 3 by 6 inch mold (manufactured by Castin' Craft) but it's definitely not a requirement. If you choose to use a different mold you'll need to adjust the project accordingly.

6 to 8 ounces of resin (and appropriate catalyst, if necessary)
I used a polyester resin but a 2 part epoxy resin would probably be safer. Any clear resin should work.

black resin dye; blue, yellow and pearl optional
Manufactured by Castin' Craft, available all over the internet.
To get the blue and yellow colors to 'pop' in front of the back you'll need to add some pearl (or a tiny bit of white instead of pearl.) If you don't add the pearl/white the color will be most obvious when it's lit but not so obvious when it's turned off.

If you're a fan of cosmic debris like I am. I used some silver 'holographic' glitter and some silver star shaped glitter.

2 part clear quick-setting epoxy

You'll only need a little, and you may not need any at all.

LED lights (5mm white superflux are used here, but almost any should do the job)
This pattern requires 10, you can use as many as you want.
A good photo/diagram of what I used is available here:

This is wired up with 24 gauge silver plated beading wire. The fixture is low-voltage and the wires are all encased in the resin so insulation isn't necessary. Light weight wire is definitely the way to go for this project.

batteries and an appropriate holder
2 CR2032 batteries and 534-1026 holder

1 resistor
56 ohm 1/4 W based on this calculator
If you use a different number of LEDs or different batteries you'll probably want to double check what resistor to use.

1 on/off switch
purchased at a home improvement store, just a basic on/off.

a set of electrical 'alligator clips' for testing your leds/connections/etc.

waxed paper
5 small, strong clips
masking tape
pliers (2 pairs is nice, but not necessary)
a screwdriver (probably Phillips, but check your switch to be sure)
assorted standard household items

Step 2: Make a Pattern

You'll need a pattern. The big dipper would be the first choice of most people, so I didn't choose it. The little dipper would be second, so, again, I didn't choose it. I went with Leo because (1) it's the best one (2) it fit nicely in the size mold I had chosen.

Use an image search to find a star chart that includes your choice of constellations (or use my pattern.) You could, obviously, just make one up as well. Import that image into Illustrator or some other draw program. For this size mold you need to adjust it to fit within a 2.5 inch by 5.5 inch space. You'll need a bit of margin around the outside edges. Draw a little circle for each star you want to include. Draw about a 1" circle for the battery pack and another .75 inch or so circle for the switch. You'll place these in a few minutes.

You need to draw one line on one side of the stars for the positive wire, and a line on the other side for the negative. These lines can NEVER touch. If you're experienced in electronics you can probably skip over the next paragraph, if not read on.

The positive line will need to touch the positive side of each LED, will need the resistor added to it, will need the switch added to it, and will need to end on the positive terminal of the battery holder. The negative will need to touch the negative side of every LED, then go directly to the negative terminal of the battery holder. This information is important when placing the switch and batteries.

Adjust the constellation in the 2.5 by 5.5 inch space until the end of the wires can connect to the resistor, switch and battery pack without touching each other. This might take some crafty planning and adjusting. I've included a wiring diagram of mine for reference. Be sure to orient the battery holder so that you can easily change the batteries (if the open side of the holder is next to the wall you'll have to do a lot of prying to change your batteries.)

Draw a 3 by 6 inch rectangle around all of it, group it and flip it. It needs to be reversed because you build the light from the front to the back, so you're looking at the back of it while you're working. I printed mine twice on the sheet so I had one to place beneath my mold and one for clear reference, taking notes on, etc.

Print it.

Step 3: First Layer

This probably goes without saying but:
Resin is toxic, dangerous and can be damaging to many surfaces. Keep it well ventilated, away from kids and pets and on a well protected surface. Epoxy is much the same - it can be dangerous and it's very permanent on may surfaces. All of the products included in this project come with safety labels and it's important to read them. One thing I've done is make a list of the chemicals I work with so that if I ever do have a health problem it'll be easier for the medical staff involved to fix it. That said, on to the resin casting.....

You start working from the front of the light - what is the bottom/first layer now will be the front when it's completed.

Mix up about 1/2 ounce of clear resin (according to your manufacturer's guidelines). You can add some glitter or other cosmic debris of your choice to this if you'd like. Catalyze it and pour it into the mold. Tip the mold around to make sure resin covers all of the bottom of the mold, and it's good to let it get up onto the sides a bit.

Let it harden completely.

If you've decided to add a layer of blue/green/yellow/pearly colored haze this is the time to do it. Mix up another 1/3 to 1/2 ounce of clear resin, and again add glitter if you'd like. Pour it into the mold and make sure it covers the front. Add a drop of each color of dye into it then swirl it around with a toothpick. Keep adding dye and swirling it until you like it, then leave it. Seriously. Don't touch it any more until it's completely hardened. If you start working on this and really mess it up just pour it out into something other container to harden up. The reason you do this now instead of with the first layer is that the toothpick can leave marks on the mold that will show on the front of you light. These are permanent to the mold, and no one wants to hurt their mold.

The LEDs behind dye diffuse and glow, while the LEDS without dye in front of them appear as more of a clear point of light. Your choice is all about the aesthetics.

Step 4: Electrical Set-Up

Now you need to do a little electrical work.

If you've never used them (and I hadn't before I made this) alligator clips are just an easy way to test out your LEDs. You'll need a pair, and some wire to attach to the clips (unless you find some with wire already attached.) I bought the insulated wire that was next to the alligator clips, it's 14 gauge. Cut 2 reasonable chunks of wire - around 6 inches - and strip a half inch or so from each end. Attach one end of each wire to a clip.

Put the batteries in the battery holder. Attach a clip to each terminal. Grab an LED and touch a wire to each side of it. This will help you figure out positive from negative. When it lights up you've connected the positive battery terminal to the positive side of the LED, and vice versa. On mine the negative side was notched at the corner. Check all of the LEDs you're using, because you would be really bummed to put out all of the work to make this and then have one not work. Be sure sure sure you know positive from negative.

Step 5: Attach the LEDs

You've come to a bit of a fork in the road, so to speak. At least your first time around do it this way:

Set the mold on top of the pattern. Be sure you know which way to orient the positive and negative sides of the LEDs. Think about how you'll handle curves. I've included a sample diagram for a 90 degree turn.

At this point you are effectively gluing a round LED to a flat surface with the glue equivalent of honey. You'll need some time and patience.

Mix up a bit of the clear 2-part epoxy. Put a drop where there's supposed to be an LED. Place the LED face down. It'll probably tip to the side. Use a toothpick or similar implement to set it back upright. You'll have to do this about 3 million times before all the LEDs are set. There's a good chance there's a better way to do this, and if you come up with it, post it. It's very important that when it's all set up and dried the backs of the LEDs are parallel to the bottom of the mold. Having the back completely exposed is what will allow you to wire it. You'll want a little 'cocoon' of clear epoxy around each bulb, this is what sends the light to the front of the fixture.

Your other choice on how to do this step is to pour another layer of clear resin (around 1/2 an ounce) and set the LEDs in that. This may result in more light coming from the LEDs, but it's also more difficult than gluing each individually.

Step 6: Seal the LEDs in Place

Once the LEDs are set, mix another 1/2 ounce or so of resin, but this time dye it black. Very black. Then pour it in carefully, as shown in the photo. You may need to do this more than once, but it is very, very important that the black resin not cover over the backs of the LEDs. The more opaque it is the better your results will look. This layer of black resin is what will keep the wires, switches and batteries hidden from the front. You can fill it up to where it's about even with the back of the plastic part of the LEDs.

Again, let this harden like you mean it. You may have been able to get the rest of this done in one day, but now it's time to leave it overnight. Dye tends to slow the catalyzing of resin so don't do anything with it until it 'clicks' when you tap on it.

Step 7: Build Up the Sides of the Box

Cut 2 strips of cardboard that are about 6.5 to 7 inches long and 1.5 inches wide. Tape them together with masking tape. Then wrap the whole thing in waxed paper and tape it, making sure one side is just smooth waxed paper with no tape or other texture.

Using the small clips, attach this strip of cardboard to one of the long sides of the mold, as shown. Three clips along the bottom, one on each side. Use the lip of the mold to make a seal between the cardboard and mold. Trust me, resin is very viscous and it'll hold. You'll set the mold on this edge (on top of something so that the side of the mold is parallel to the ground). I set mine on the box of waxed paper. I also ran a strip of masking tape from the now top of the mold to the table to prevent it from accidentally falling over.

Be sure you do this over some scrap/newspaper because it is possible to drip a bit. Mix up 1/2 an ounce of dyed black resin (add glitter if you'd like, it'll fall to the bottom and show in front of the black). You'll pour this over the cardboard to fill in the side of the mold. It'll be about 1/4 of an inch of thickness for this wall. Leave the whole thing set up this way until the resin hardens up. Then unclip it, carefully peel back the cardboard strip and repeat. I used 1/2 ounce for each of the long sides and 1/4 ounce for the short sides.

Again, leave it overnight to get solid because you'll abuse it tomorrow.

Step 8: Wiring

This is my first wiring project (with the exception of installing light fixtures in houses). I'm not sure if this is all technically correct, but it works.

Cut a piece of 24 gauge wire that's about 3 feet long. Fold it in half. Hook the 'folded in half point' over the last prong of the LED at the furthest end from the batteries on the positive side. While being as gentle as possible, wind the wire in figure 8's between all of the prongs on that row of LEDs (only the positives). When you get to the end go back with the pliers and bend the prongs down onto the wire. The idea here is to get it all pushed as tightly together as possible.

Repeat this on the negative side.

There's an excellent chance you'll pop an LED out. If you do, push it back into place and finish the wiring. Mix up some more 2-part clear epoxy and use that to glue it back down. Make sure the glue seals it all the way around, otherwise black resin can seep in front of it and hide it.

At the end of the positive line cut the wires off 1 or 2 inches from the last LED. Twist those wires together with one wire of the resistor. If you've got enough wire left from what you just cut off twist it to the other side of the resistor. From here through to the battery be sure you allow enough wire to place the switch and battery exactly where you want them. Connect those wires to one side of the switch (the 'lead' side, if the package gives you a 'lead' and 'load' diagram.) Cut off any excess. Attach the trimmings (or new wire, if necessary) to the other side of the switch and then to the positive terminal of the battery holder. Twist it around the positive side a bunch of times, making sure there's lots of contact. Trim any excess wire. Any of this wire can be super glued in place to tack it while you're working. This may help keep the switch or batteries where you want them until the final cast.

Connect the negative LED line to the negative side of the battery pack. Again wrap the wire around the negative terminal a bunch, then trim the extra.

Carefully flip the switch to turn it on. Make sure the LEDs all light up. If they don't you can probably make them by adjusting wires and checking connections. Once you have it all just right mix up more of that 2-part epoxy and put a dollop of it on every LED. This will set the wires in place and protect the connections. Keep the light on while this sets up so that you can make any adjustments (sometimes epoxy will slide between the wires enough to take out a light, but you can get turn it back on by pushing on it with pliers or a toothpick). Keep making adjustments until everything is working and the epoxy sets up. Make sure it's really, really dry before the next step.

Step 9: Last Layer of Resin

Double check the placement of the switch and batteries. Mix up at least 1/2 an ounce of dyed black resin. Pour it into the mold to cover the LEDs and fill in under the switch and batteries. It may well take more than 1/2 an ounce. Just be sure you don't pour so much in that you disable the switch or make it impossible to remove the batteries. Once you're happy with the amount of resin leave it to set up.

Step 10: Removing

Carefully pull at the sides of the mold to release the cast piece from the mold. You'll be able to see from the outside where it's been pulled loose. Keep flexing the mold until your light pops out of it. Doing this gently will help prevent damaging it. Even when resin seems hard it's still hardening up. It'll keep hardening for days after it's finished (sometimes longer.)

Step 11: Turn It on and Admire

Flick on the switch and enjoy your new light.

You may need to lightly sand down the edges of the resin along the walls (where the top of the mold was). Otherwise it should be completely done.

If you'd like to keep the back covered up you could cut a piece of felt or something similar, cut a hole for the switch and glue the felt along the top edge. Velcro could also work. This would enclose the back, but isn't too important if it'll be close to a wall (like mine is.)

There are an infinite number of appearance and size variations, but the procedure would remain the same.

The method for building up the sides of the mold is one I've been working on for a while. It opens up a wide range of possibilities with resin while avoiding making a 2-part mold (with one part being used to keep the center of your shape open.) It could be valuable on large pieces simply to keep them lighter and use less material.

One other idea I've come up with since posting this is to add a 'glow in the dark' powder in with the cosmic debris. This would allow it to give off a soft glow all the time, even when it's turned off. I haven't tried it, but maybe something like this:

That would also be an appealing option if you wanted to try the resin casting without all the electrical.
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