Thread: LED candles from scratch

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I should preface this by saying it's not really a *fast* process and it's not really cheap unless you have supplies on hand already, but I'm pleased with the results and wanted to share in case there's some useful bits for others to learn from. I have lots of pictures since that's what I tend to learn from best.

I had some very specific requirements for some electric candles. It seems like it's always windy or rainy (or both) here on Halloween, so 'electric' candles make good sense. I also wanted something very durable (toss it all in a box when you're done) which eliminates real wax candles. Since I wanted to use hot-glue webcaster cobwebs as well I wanted something really low heat too, so LEDs are a natural choice. I also wanted something that looked "authentic" in full scale, so that eliminated a lot of store-bought stuff-- and it's fun to make things anyway.

So-- I ended up with urethane plastic LED candles. Here's what I did...

I started with the flames. I bought a block of "Sculpy" clay (works like a modeling clay and hardens in an oven at 275F-- $9.95 for a huge block at a craft store). I looked at the size of a burning candle flame and rolled out some shapes by hand and baked them per the instructions.



After the shapes cooled, I hot glued them in groups of five to a popsicle stick and made a simple mold to hold some liquid silicone mold making compound. I used Tap Plastics Silicone RTV system (1lb for ~$24), but urethane rubber or even latex molds would work. (I like silicone because the liquid plastics won't stick to it.) After the silicone set overnight I removed the Sculpy masters by just pushing on the bottom of the mold and poured in Smooth-On's Smooth Cast 325 liquid plastic. It's a clear, amber colored liquid urethane plastic.



Smooth Case 325 is *fast* setting stuff-- hard in maybe 10 minutes. You could use pretty much any translucent plastic (EasyCast for example) or even 5-minute epoxy. Tints can be used to color the plastic-- I just left it natural. Once the plastic sets up the 'flames' can be squeezed out of the mold



I put some 100 grit sandpaper on a hand-sander and sanded the bottoms of the flames flat (light will enter from the bottom). The LEDs I'm going to be using are flat topped, but if you had the rounded LEDs you could drill a hole in the base to hold them.



As a simple test, I just put a couple of the flames on top of some LED strip-light I had from another project. Note that pretty much any light source will light these up nicely. It could be any high-brightness LED or other lamp. Colored LEDs will tint the light from the 'flame', so it's easy to experiment. These are a reddish-orange setting...



(Note that at this point, you could just drill a hole in a real candle and use these plastic 'flames' with an LED under them and be good to go. Since I wanted an extra "tough" factor I went with fully plastic candles too...)

For the candles, I started with some paraffin wax candles from the craft store. (12" candles were 5 for $10) I didn't need them full length, so I cut them into irregular sizes and dripped wax from another burning candle on/around them to give it a nice "used" look. Since I was planning on using these on top of some skulls I've been making that's how I mounted the candles-- but you could put them on a flat surface, or whatever you want for your purposes.

Around each candle I built a small 'dam' out of sculpting clay. This keeps the silicone molding compound from spreading and helps keep the edge of the mold thick so it's less likely to tear.



One again I used the Silicone RTV mold making compound. With a disposable brush you brush on multiple layers of the silicone, adding a fresh layer once the previous one has set up to a 'tacky' point. I did three thin coats to capture the fine details of the wax. Smooth-On's website has TONS of great examples of how to make molds with various techniques. Really educational if you're interested in the topic.



After the 3rd coat, I added a little "thixotrophic" additive to the next batch of silicone. That allows it to be spread more like a paste. I built the layer up to about ~1/8"-3/16".



(to be continued...)

After an overnight cure, the silicone can be removed from the 'masters'. Start by removing the candles from the base-- the candle wax should be visible from the bottom and you'll have a nice silicone rim around it.



I sprayed a little mold release on the *outside* of the silicone mold because I want to be able to turn it inside out while removing the candles. Then, while holding the rim of the mold with two hands I simply pressed the top of the candle against my knee-- that turns the mold inside out and forces the candle out of the silicone. The wax will break up, but that's fine. We're just interested in the mold.



With the mold completely inside out you can pick out any remaining bits of wax. I also looked for any 'hoops' (or loops) in the silicone and cut them (or pulled them out). You don't want anything that would form something like the handle of a coffee mug-- you need to be able to pull the mold off the plastic in one piece. Here's a mold inside-out:



Casting is just a matter of pouring in some liquid plastic and massaging the mold and slushing the liquid around so that it forms a hollow coating on the mold. As the plastic starts to set (it'll turn from the consistency of motor oil to more like syrup, then molasses, then finally fully gel) I keep turning the mold making sure it's evenly coated.

For these candles (4-8" tall and about 1.5" in diameter), I ended up using about ~40-60ml of the Tap Quik Cast urethane plastic. I added some black tint since I'm planning on painting the candles to give them a little more depth and the black is more forgiving than the natural ivory color of the plastic. After about ten minutes the Quick Cast can be removed from the molds the same way as the original candles. You wind up with perfect little candle-copies.



Here's one shown on top of the skull for reference:



In the top of each hollow shell I drilled a hole that's the same diameter as the light emitting lens part of each diode. (The little square with wires is the particular surface-mount white LEDs I'm using. They're a "warm white" color which makes a really nice/natural yellow from the amber colored plastic.)



A dab of hot glue holds the LED in place inside the hollow candle. The wires exit the bottom to be wired up to something else later. (This is just a "test" candle-- the real ones will use longer color coded wires!)



With the LED in place another dab of hot glue and you can stick one of the flames to the top. (I like it that all the flames are unique-- looks a bit more natural than the identical ones from stores.) Although I guess it shouldn't surprise me, it looks remarkably like a candle.



Finally-- power applied. It's hard to photograph, but even with just constant power (no flicker or anything yet) it actually puts out a very realistic 'candle amount' of light!



(and a little but more to continue...)

I like it!!!

With the lights off-- you'll see that both the amount of light and the color of the light is really like a candle.



However you color the plastic or light it will set the color/mood of the candle. Being an electronics-type guy I designed a little controller that will light and flicker the candles in various ways. Once the circuit boards show up and I get the code written I'll post a video or two.

If you used a translucent plastic that would also improve the "lit" candle look as well, but I'm happy with what I've got for now.

I hope that this gives you some ideas or inspiration. It's more involved and time consuming than some other ways to do it, but it does provide a solution to a particular problem. Happy haunting!

-Clay

That is a great tutorial! Thank you!

Eric

I decided to try using some of the same casting resin that the flames are made of to cast an entire candle. I added three drops of Smooth-On "So Strong" red tint to 60ml of SmoothCast Color Match 325 resin and ran it in my largest candle mold.

From there I repeated the LED installation and flame attachment. The transparent resin lights up in a suitably candle-like fashion:





Then for comparison, I painted one of the opaque grey candles I showed earlier:



I kinda like 'em both. Not sure which I'll use.

Here's a quick pick with one of the skulls painted up:



(the candle is just sitting on top-- it needs to be mounted and have some more "run-off" added to look better)

-Clay

Right on!!!

Finally took some video with a few different lighting selections (kinda hard to tell the differences in the video-- the camera tends to brighten things up a bit).

That looks really good.

I like the second one that you painted. It looks more creepy.

What did you use to 'flicker' your LED's?