String bet question

[johnp158]

I know I'm not the expert on this, but it doesn't sound like anybody else is either. A couple of people seem to be under the impression that as long as you announce "raise," you can keep going back to your stack. That can't be right. It seems like the question comes from the fact that he is still in the process of stacking what's left in his hand when he says he wants to add another 25. I would lean toward thinking that it is a string bet, but by no means am I sure.