This is a very old technique for making hollow metal beads.
If you try this you will realise why jewellry was so highly prized prior to the era of modern manufacturing, even if only made of base metal, because of the labour intensive nature of the process.
Step 1: Materials
You will need:
Two disks of copper or silver.
Doming block, punches, and a hammer. I have used a jewellers repousse (pronounced re-puce-say) hammer
Blowtorch and Charcoal Block
Pickling solution. See this Instructable for how to pickle metal.
Files, wet or dry paper, solder.
Don't forget to wear safety glasses and make sure you can use all of the tools safely.
Step 2: Anneal the Disks
Annealing is the process of heating metal up and allowing it to cool slowly. This alters the crystal structure of the metal and makes it very soft. Note: Aneal can be spelt with one n or two depending on which side of the atlantic you are.
Heat the metal up to what metal workers reffer to as Cherry red. Allow to cool.
Now pickle the disks to get rid of firescale. See this https://www.instructables.com/id/Pickling/ for deatails about this.
Step 3: Start the Doming Process
Use the punch and hammer to force the disks into one of the depressions in the block.
Sadly after a few blows of the hammer something strange will start to happen - the metal will become progressively harder! This process is known as Work Hardening. You will need to stop and anneal the metal again to make it soft.
Return to the doming block and use a smaller depression to increase the curvature of the piece. If you want to make an elipoidal bead you can stop here. If you are going for a sphere you have more work ahead of you.
Nobody said it was going to be easy!
Step 4: More Doming.
Here you can see two of the later stages in the doming process after the annealing step.
Step 5: File the Edges Level.
You should now have two dishes or hemispheres of metal.
Unfortunately all that hammering and heating will mean that the edges won't join neatly,
File them flat. Finish of by rubbing the edges on some 240 grade wet or dry paper.
Don't forget that your file should have a safe edge- keep this towards your fingers.
Step 6: Join the Halves.
If I was doing this for some serious jewellry making, I would use silver solder. This has a much higher melting point and would let me do enamelling., or conduct further soldering opperation using solders with progressively lower melting points.
In this case, for demonstration purposes, I used soft solder (lead free of course) used by plumbers. I balanced the bead on an olive (not the fruit, the thing that you put in a plumbing compression joint.)
Here you can see the ring of soft solder. I just heated it up with the torch. Make sure that you have something handy to steady the bead while it sets, as the two halves can slide apart.
Here are the two beads I made today.
They are now ready for finishing by filing sanding and polishing and finally drilling.