20 minutes of clorox is not very long, but it will never come out of the bone. The bone will get a chalky texture and maybe some parts will look as if they are peeling? It's hard to say. The Sun light does not Ruin the bone quality it shrinks the bones significantly when allowed to dry in the sun. The sun also increases the power to make the clorox work at the whitening process.
Boiling is horrible on animals that are not fully mature. It's OK to simmer a skull in near boiling water and scrape and peel the meat off as you can. It's just horrible to have a skull in a rolling boil for any length of time. The tooth sockets begin to shrink away and the teeth are loose and don't fit properly. Then the bone sutures start to seperate making the skull look as if it was several pieces not one big massive bone.
On older animals this is not as big a problem but Bears under 5 years old will show definate suture lines and seperation when boiled. The Zygomatic arches tend to peel and flake when boiled and certainly when exposed to clorox bleech. I suppose if these things don't seem to make sense you need to see what a skull looks like that was not boiled, bleached, or exposed to sun looks like to compare them. There is no comparison!
In a future issue of Bear hunting Magazine I have an article coming out telling how to age your bear by the condition of the skull and teeth. It will be a photo intensive article. You will see lots of high quality photo's of professionally finished skulls then.
