Do we know what powers the ring gives to a dwarven smith?
Would he be able to find a way to escape incoming molten metal the moment he put his finger in a 2 ton steel sphere?

What if he ends up with the power to mould metal by thought? He might just manage to deform the same piece of steel and use it to prevent the molten metal from getting to him and then use it to create stilts and a shield for incoming guard attack?

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Ok, maybe they can just make a cast, separately, away from the ring’s influence and then get Frodo to drop the ring in the molten metal right after it part of it has been poured in.
But what if the ring ends up floating or sinking during the hardening (cooling down) process, making it accessible to touch, but at the same time, hard enough to detect?