To make the candleholder, the first thing you'll need is some pipe fittings. They are easily acquired at any plumbing supply or hardware store. I got mine at Center Hardware in San Francisco for 40 bucks. They didn't even seem to mind me sitting on the floor playing erector set as I worked on my design. You can use galvanized or black iron pipe, but the black pipe is cheaper so I went with that (see next step for full parts list).
About Powder Coating
Powder Coating is an electrostatic process where a charged pigment dust is sprayed into the air with a handheld gun. The pigment particles become positively charged in the gun and stick to the part which is connected to ground. You see powder coating all over the place: bicycles, motorcycles, park benches, cars. My initial impression was that it looks so good I figured the process would require expensive equipment or some hard-won skill. Turns out neither is really the case--you can powder coat at home with an inexpensive kit and an electric oven.
Powder Coating Kit
The powder coating kit I used was $140 online from Eastwood. The deluxe kit comes with two free colors, so I picked red and yellow, both very vibrant. You'll also need an air compressor with a regulator that can be set to 8 PSI. Pretty much any small air compressor will do, and if it doesn't have a pressure gauge, just pick one up with 1/4" NPT fittings.
To flow and cure the powder coating for small parts you can use a toaster oven, but for this project I wanted to assemble the pipe fittings into several large segments and coat them all together, so I needed a bigger oven.
One gotcha is that you can't use a gas oven to cure the powder coating, so the thing that made this project more complicated was getting and installing an electric range (my house only has gas). In the end I was glad I did, because I wouldn't want to eat anything out of the oven I used anyway. I picked up a used electric range for $75 off of Craig's List.
Another gotcha is that you have to thoroughly clean your parts. Oil, dust and any label glue on the iron will prevent the powder from sticking. I boiled my parts to get the labels off then cleaned them with acetone (outside).
Finally, remember that the powder pigment is a very fine dust and will easily coat your lungs and get in your eyes, so get a NIOSH-approved respirator and wear goggles while working. You'll need a workspace you can sweep or hose down after the dust settles. I made the mistake of leaving the door open between my workshop and a room where I keep some computer servers. Afterward, I noticed the server filters had turned red and yellow from all the powder they sucked in. But it all vacuums up or blows off easily.
These little things aside, this project was doable over a weekend. Ok, on to assembly!
Step 1: Assemble the fittings
I used all 1/2" NPT fittings (normally for natural gas). Here's my part list for this design:
4 - 90 degree elbow
4 - 3" nipple
2 - Side outlet tee
3 - 6" nipple
Note: This list is for two tops and holds four candles
2 - 90 degree elbow
2 - Close nipple
2 - Side outlet elbow
4 - 2" nipple
4 - 45 degree elbow
Be sure all the identical parts you're buying are actually the same. Sometimes stores stock several different brands, which could have slightly different external dimensions. This could make your candleholder look asymmetrical or skewed (could be nice too if you intend it).
Be sure your pipes are clean. I boiled the ones that came with labels, then wiped them down with acetone (outside). Dirty parts will prevent powder from sticking. The professionals will media blast (sand blast) the parts first, so you might do that if you have the equipment. After cleaning, it's good to pre-heat the parts in the oven set to 500 degrees F. This will burn off any dirt left over. After the parts cool completely, wipe them down again with acetone and a fresh rag.
Hand tighten all the fittings, then use a pipe wrench to secure them and get them into their final positions. You can use two pipe wrenches on adjacent parts or a vice to precisely position a stubborn piece.
Step 2: Powder Coat
Preheat the oven to 450 degrees F (or the temperature appropriate for the powder you are using).
Powder coat the Candleholder Tops
Hang the assembled Tops using steel wire from an oven rack. A good place to attach is to the threads between two fittings. You can fit about eight of these at a time, or just two if you're making a single candleholder. Test fit the parts in the oven before you start up the powder to make sure they don't bump against the walls, heating element, or each other.
If you're using a toaster oven, insert high temperature silicone plugs into the elbows to support the part on a baking tray.
Clamp the oven rack between two supports - I used a ladder and a board. Attach the ground clip to any metal part of the oven rack. Now plug in the powder gun, fire up the air compressor and apply the powder.
You want a good dust cloud evenly dispersed around the part. Concentrate on the most deeply recessed inside corners first, and carefully move the gun around the parts to get an even coat. Remember, the electric charge is on your side, it will pull the dust toward the part and make it stick.
Step 3: Cure the parts
Transfer the parts to the oven
Very carefully unclamp the oven rack and carry it to the oven. It's good to have a second person who can open the oven door for you. Gently slide the rack of parts in the oven and close the door. Check the parts every five minutes. The powder will gloss over and have a wet look to it. With my setup, this took about 7 minutes at 450. Once all areas of the part have become glossy, turn the oven down to 400 degrees and cure the part for 20 minutes.
Cool the parts
Remove the parts from the oven and hang them again to cool. I used the drawer from the bottom of the oven so they stayed suspended. After they're cool, the parts are ready to be used. Just detach the wire and that's it.
You should only need one coat but if there are any parts that got underserved or places that weren't quite clean enough for the powder to stick you can repeat the process the exact same way. Hit the lighter spots with powder first to make sure they receive adequate coverage the second time around.
Step 4: Final assembly
I chose taper candles that also have conical bottoms which are easy to screw into the top fittings, but pretty much any candle that can fit will work.
Since these are real pipes I think it would be interesting to outfit them with a propane feed and mantles to make a gas lamp. I've also seen the pipes used as an oil lamp. Since you can individually powder coat the fittings, it's possible to make really big sculptures even with a small oven. I'd like to build some kind of multicolored towering structure.