On 1 July, 20:45, "Tim Downie" wrote:
I've an idea to create a memorial post for a departed friend which would
consist of a domed metal cap on a 4"x4" post.

Copper. Easiest to work, patinates nicely afterwards.

Tools are a variety of wooden, plastic or rubber mallets and also a
mix of treestumps with hollows in, or else sand-filled bags. Most
importantly, some sort of gas torch (or cooker) for annealing. You
need something with these tools, but they're not fussy and it's easy
to improvise. A cheap wooden egg mallet, or just a home made "lump on
a stick".

Source metal is scrapyard immersion heaters, or other scrap copper.

Web searching should give you techniques, otherwise any '50s school
metalwork handbook. Look for "sinking" and "doming"