I was watching a show a while back which made mention of ways to solder copper pipes with some water in them. They mention the age old trick of a piece of bread and another method involving a wax like capsule. This capsule is inserted into the pipe about 8-12 inches and plugs the entire inside of the pipe. When the joint is sweated and a new valve or fittings all have been installed one simple applies the heat of the torch to the area of the capsule and it melts it.
I have been searching the web high and low for these capsules and wanted to inquire if you knew what their proper name is and also if you know where to get them.
I've used the bread trick and its good and bad depending on how much work you need to do. I've seen a Jet-flex but thats a bit $$$ for me.