Hi Aaron,
Whatever works is the final word I suppose. So forgive me if I add a few more comments on this procedure. The more experience you have with soldering a variety of metals you will notice differences in thermal conductivity. This is a big factor when soldering silver and copper alloys. Higher thermal conductivity effects how much heat input is required to get solder to flow and this can also affect warpage and distortion. You will also notice that heat induced distortion will vary not only with specific materials but also how the actual parts were manufactured ie. casting, machining, 3dp etc. All of these factors can be compensated for to produce good results. It is largely a matter of experience when determining the best procedure for any given job.
Silver has an extremely high degree of thermal conductivity so it is essential to preheat the entire part before concentrating on the area to be soldered. It is safer practice to flux the joints prior to ANY heating as oxides will begin to form even at relatively low heat. The pre heating should be done by holding the torch flame several inches away from the parts, like 2x or 3x further away than when you are actually soldering the joint. Be patient, take your time. "Slower is better" should be your mantra. No harm is done until you overheat/burn the flux. No amount of praying or cursing will help once the flux turns black. You must quit and scrupulously clean the joint area and try again. Invest in failure and learn from it! Anyway, after a gentle overall preheat, you can now bring the torch in closer to the joint area, but resist the temptation to point the flame directly on the joint. Keep the flame dancing around the joint area. Do NOT concentrate the flame in one area, EVER! Watch for the flux to change, it will appear clear and much cleaner than the unfluxed regions. The solder should now flow instantly into the joint. When it does, back the torch way off for a few seconds, playing the flame around the whole part in a circular motion and you're done, allow to aircool. These principles are the same whether you use low temp lead/silver/ tin solders or high temp industrial silver solders. The big difference being, you are much closer to the edge of disaster when using hi temp solders!
As to minimizing distortion: Often times some form of
fixturing is required. Jewelers/metalsmiths traditionally use what is refered to as "binding wire", this is fine gauge uncoated steel wire usually between 20g-30g. On large parts heavier gauge "baling wire" can be used. On your piece I would have fashioned a temporary ring clamp by twisting together the ends of a short length of binding wire and slipped this loop down to to the widest area of the part to hold all the "petals" in alignment. Using a pair of jewelers needle nose pliers you can adjust the tension of the wire to gently bring parts into contact which will produce cleaner and stronger solder joints. Avoid over tensioning as this can cause more problems that it solves.
So, if it was me soldering this piece, I would have set the part vertically on a fire resistant brick, not used a vice, maybe a tweezer clamp at the base for stability. Used some binding wire, fluxed the top 1/2" of the part, layed a snippet of solder on the joint, started a slow preheat at the base of the part (count 20-30 seconds), by now heat should be even throughout the part, then a quick burst of heat near the top, voila job done. But, as always, the important thing is....whatever works!
-G