What do you mean by “petrified?”
If you mean hard, what I do is gently use a damp paper towel to try and remove it.
That often doesn’t work for me, so what I usually do is turn the faucet onto a fairly warm temperature, but not too hot. (But also not too cold) I would say maybe warm shower temp.
Take the chick, and run it’s butt under the warm water, I usually do this for about a minute of it’s fairly bad. No need to turn the chick upside down or anything. It’s ok if some water gets on it’s back, but try not to get water on their face that much. Basically what you are doing is moistening the poop so you can easily wipe it off. Once a minute or so has passed, or it seems like it is good, gently with a damp paper towel wipe the poop off. It should be all gone. (Note, the chick will most likely peep and scream at you when your doing this, but it’s for the better good.)
Make sure to get the chick as dry as you can. I usually dab off excess water, then make sure the brooder is nice and toasty. (I lower the heat lamp a touch) and wait for it to dry off. Once it’s done drying, raise the heat lamp to the regular position. (That is, if your using a heat lamp.)
If your referring to something other than dried on pasty butt, hopefully someone else can help.
Sorry no ones responded yet.