The hottest part of the flame is outside the "blue cone" beyond the fuel rich (cooler) blue cone area. Direct heat to where the heat is going. Also, just a helpful tip, placing solder inside the bezel when joining it and especially when soldering the bezel onto the back plate will eliminate solder scarring and facilitate clean work.
Refreshingly accurate description of what happens to join two pieces of metal (with solder). I shall assign this video to my beginner students. I would love to see (hear) the explanation (by someone other than myself) of why hard solder can be used for all joins, consecutively. Thanks!
The solder paste stays pretty well in the tube as is. Some people put sewing pins down the tips if they leave the application end on to prevent drying. Hope this helps!
You must be using fine silver for the small pieces, as you are not showing that there is a need to pickle the small piece before soldering to the larger one
