It is true that the hardness of the gold does depend on how you
alloy. I don’t alloy myself though, so I am speaking as one who
buys stock from suppliers. In general…the higher the karat of
gold, the cleaner and softer that it is (again, allowing for
different alloy mixtures of course).
In my experience, working with 10k isn’t very rewarding for
fabricating, espescially if you are doing so with the intention
of eventually moving to higher karat gold. 14k or higher, is not
only easier to work with, but much more attractive in the
outcome. Also, because different golds are different to work
with, I would suggest learning on whatever karat content, and
alloy mixture that you eventually intend to be using…your
skills would be best developed in that manner.
My metalurgy skills are limited, so I won’t try to explain try
hows and whys behind it ( Im sure someone here can do a better
job in that department). I’m just speaking from bench