Apparently copper is one of those metals which remain soft after heating however it is cooled. Only work hardens. I have always cooled slowly, thinking it needed to be done that way, so as it works and it cools fairly quickly anyway, I have no burning desire to change. But nice to know it does not really matter.

If you want to keep the soldered cones in place you will need a heat sink between the section being annealed and the soldered part. Dependiing on size etc, a pair of vice grips are often sufficient. For more heavy duty applications, a large potato forced over the tube will absorb an amazing amount of heat before it can get to the soldered section. (We used to use a sort of papier mache ball made from asbestos shreds and water but they won't let you do that any more) Trick is to heat the annealing section up quickly to dull red then plunge it in a bucket of water, thus minimizing the time available for heat to travel past the heat sink. If you know where your bends are going to be, you can anneal each of those specific areas one at a time to stop heat build up in the the pipe overall.

If you have really tight curves to make, you will find it helpful to fill the pipe with something so that the bends do not collapse around the outside. Soft solder or lead can be used, and I have read that there is a plastic which works too. It has a low melting point and comes in pellet form but I cannot recall the name. Anyone?

And of course use a grooved former for the inside of the bend, too. This can be turned in hardwood to the size required, if you can find nothing off-the-shelf.

Cheers, Tim

It has been known to use sand packed into the tube, you can also get pipe bending springs of various diameters.

George.

If you have over bent a piece of copper tube using a spring, useually if you wind up the spring in the correct direction the spring will come out, but it does take a lot of effort. In former times the heating and ventilation people who used 3 or maybe 5 inch steel heating pipe would fill the pipe with very dry sand with a cap either end and using Oxy/acetylene bottles to heat the pipe would make expansion loops on long runs. Now days they will have a hydraulic bender with a digital readout and key board. I think kiln dry sand as used by block pavers would be OK but make sure it is definitely dry. When I have used sand I always put it in the oven before use to drive out any moisture, ensuring I didn't generate steam and maybe blow the sealing caps off, ruining the job. Primitive but it works.John