[quote=@JunkMail]By that logic he’d also be as unbending as steel, and as tearable as paper when he is in those states. I understand that a certain amount of creative license is necessary, but you cant just pick and choose what properties of the substances you get. I’m okay with him turning to steel, but in order to do that I expect him to act like steel would.[/quote]

.... yes. He gains ALL of the properties of the material he turns into. So when he turns into steel, he acts like steel.

[quote]His muscles retain their function as his body becomes a series of interlocking joints and hinges so as to maintain the full range of normal movement even while he's made of steel.[/quote]

I understand that it's important to be critical, but this is something that's specifically addressed in my description of the power. The only 'creative license' is that his muscles still somehow function even when made of steel, but that's pretty much a requirement.

[quote=@JunkMail]There’s a balance to this that I mentioned to Wraith where he only transforms parts of his body in cases like this. For example, his arm from the elbow down is steel so he can still strike things and move.[/quote]

Why? This power isn't overpowered, so I don't see why you feel the need to inflict such a massive nerf. If he weren't able to transform his full body he'd have died in his first fight against a knife-wielding thug. 

[quote=@JunkMail]Is there a specified amount of the substance he requires to transform? I ask because he can carry around marbles of whatever substance he wants and change whenever he wants.[/quote]

I'd say he needs at least a marble-sized quantity. And yes, if he could acquire a marble of the material he could carry it around to transform. At which point he could indeed pull it out of his pocket and change whenever he feels like.