The chandelier is progressing! The center spindle is turned and I am starting with the milk paint samples. The "arms" will be bent around forms. The material I will be using is 3/8" lamp tubing. I selected aluminum as I think it will be the easiest to bend. I will fill the tube with fine sand and slowly bend it around the forms.
I will need to paint it, most likely flat black. Wondering about the best way to go. Primer? Or just paint?
Advice would be great!
The milk paint in Curtis Bucann' s videos was very helpful.
Sand with a grit that will that will give it some tooth. Probably 180 or 220. Milk paint bonds really well but a liite somthing for it to grab onto will really help. Might not streak as much when you paint it also. May take 2 coats. Milk paint keeps fairly well in a sealed container refrigerated so mix enough to be able to do multiple coats.
My experience with aluminum is that if you want the paint to stay on long term, use a good aluminum primer. I would remove any ink stamps and discoloration due to welding.
Question, what is the radius of the bend? Filling with sand is a great way to keep the tube from collapsing but if the radius is too small you might still get buckling on the inside. If you have trouble bending consider that the aluminum might need to be annealed. (Unlike steel, aluminum is annealed by heating and and quenching.) Sometimes working metals may require repeated annealing. I'd try it first on a spare piece or two.
Some aluminum alloys can be worked easier than others. If the aluminum doesn't bend satisfactory you might look into copper. You can buy copper pipe that is made for bending. Or look for thicker wall aluminum. Or use steel and heat red before bending.
When I worked in a plant that prepared piping for nuclear power plants they bent even very large and heavy wall steel pipe with the sand method, bending after heating the pipe red hot. It was important to pack the sand well and they did it with powered hammers, jarring the pipe for hours. For small diameter tubing you might pack it by capping the end, holding it vertical, filling with sand (I'd use as fine as I could get) vibrating or tapping repeatedly up the sides of the tubing, cap the top end, then bend around the form.
To bend it's not recommended to simply press the middle of the tubing into the form, but clamp the tubing at the beginning of the bend then pull it around the form. (Sorry if you know all this.)
If you run into insurmountable problems a tube bending company could do it easily. (There is a place called Tennessee Tube Bending near here) I've watched them bend very long aluminum tubing with vanes on the outside to make heat exchangers. A metal fab shop could do it too - a friend of mine recently had some stainless steel tubing bent into beautiful arcs and it cost almost nothing at local a welding/fabrication shop. I think they did the bend with a roller machine.
Before painting metals I prefer to sand blast the surface. Another method to consider is annodizing. This can give a beautiful professional look that can't chip or flake off - the color is in the metal. Annodizing can be colors other than black.
>>>Would it help to "warm" the tubing with a propane torch before bending?
I'm certainly no metallurgist but from my limited experience I can't imagine warming helping. For heavy wall steel it is heated red hot. (I'm talkin' pipes 18" in diameter and maybe 2" thick walls!) Annealing steel first will make it more malleable but that requires heating to a certain temperature (varies depending on the specific alloy) then cooling very slowly. Brass and aluminum are annealed to make them softer the opposite way - heating to a certain temperature then quenching to cool quickly, something which will harden some steels (i.e. tool steels) to the point they are brittle. I can imagine that moving a propane torch flame up and down the tubing might even harden the tubing since as you moved the flame the section just heated would cool slowly instead of rapidly by quenching.
BTW, even trying to heat and quench a long piece of thin-wall tubing might be difficult without a kiln or oven and even then it may cool too quickly between the heat and the quench. You'd have to research the temperatures required. I'd probably try sliding the thin wall tubing on a solid rod of mild steel, heating and quenching the both at once. My thinking is the steel would hold the heat better. That's just a wild idea though, heat treating metals is an incredibly complex science, one which baffles me. Just look at the diagrams for steel.
However,warming aluminum might make it more comfortable in a cold shop!
I would just get a few extra pieces and try different things to see what worked the best. They are probably pretty cheap. A sketch would be interesting.
The ice idea sounds interesting. I'm guessing it wouldn't split such a small diameter tubing if if you plugged one end and added and froze just a little water at a time. But it might depend on the (relative) wall thickness, the specific allow of aluminum, and whether it was annealed or not. Perhaps a bit of quality time with Sir Google would be beneficial.
What I did was lightly sand the aluminum, then prime using an etching primer specifically for metal. Then spray bombs of whatever color you wish. Can't recall but there is one spray paint brand that has an excellent nozzle that doesn't spit out paint.
On the second iteration of painting metal tubes, I opted for powder coating instead. Simply dropped them off at a powder coating company nearby and picked them up the next day. The finish is very uniform this way.
All that is required is a tubing bender. I wouldn't bother with the sand. You could use a bending spring but to be honest I have never seen one for 3/8". We bend aluminum rigid conduit very easily without kinking with conduit benders. Smallest trade size being 1/2" though. and If we are messing with a pipe that is already installed (possibly in the wrong place!) and trying to "tweak" it we insert a bending spring into the pipe to prevent kinking.
I've made a number of drapery rods out of galvanized top rails for cyclone fences. Very inexpensive solution compared to the pricey things you get in drapery shops. Galvanized is much more difficult to get paint to bond to than aluminum. I coated each piece of tubing with Zinsser Seal Coat prior to painting with a textured paint. They've held up for many years with no issues.
For those interested, to make them look like conventional drapery rods, epoxy in a plug of wood in each end and apply one of those screw on finial thingies into each end plug. Can't tell the difference from the expensive ones.
The black thin wall chain link top rail pipe I saw was power coated and expensive (over three times the cost of galvanized). Is there a different option available?
