engraving the stuff seems quite similiar to me compared to sterling. i have done more sterling than the argentiun. if there is a difference, i doubt it would be much. ymmv
The stuff is flogged as being tarnish "resistant". When you are trying to "blacken" it, you are basically trying to tarnish it.
You bought the wrong material if that is your goal.
The fact that it doesn't "blacken" easily is about its only claim to fame, other than higher price...
It has quite a few drawbacks for me. It shatters like glass if you drop it while it's hot. The solders made for it (that I have used so far) do not flow well and have to be pushed around with the soldering pick. Kinda like peanut butter.