Well, maybe you'll find that it pips okay through the bloody area. I'm afraid I'm a little bit of an interventionist. I have an incubator that I can't see through it's just a small one that was cheap. So I have taken peeks but since it is small it regains humidity very quickly. I had no trouble with my last hatcheven though my kids kept peeking while I was at work. This time my third egg to hatch had pipped at the same time as the second but the second zipped and hatched and the first was making no progress. I pulled back a tiny piece of the shelland the membranes still looked intact. So I poked a small hole just so some air could get in. Within the next hour he had zipped and was out. Maybe he would have done it anyway, who knows.
I usually will intervene once most have hatched but I try not to open the bator when ones are pipped or zipped. I might sneak it out for a look tonight if it still hasn't done anything. I have 6 other chicks hatch but no javas yet