Homemade Beef Stock - No impurities?? What?!

[mtf2692]

I'm making beef stock for french onion soup from Thomas Keller's Bouchon cookbook. I roasted the beef bones, a mix of knuckle bones and marrow bones, and then covered with cold water. I brought to a light simmer about an hour ago and besides for some very slight foam, there are no impurities. This seems weird to me. I've made veal stock from his cookbook before and there was really gross looking scum that I had to skim off often, but here there is none. Any thoughts? Am I doing anything wrong?

[Melanie Wong]

When you roast the bones or start with cooked meat, there's very little scum.

[Puffin3]

Did you blanch the bones and drain off the blanching water? TK specifically calls for blanching in TFL.
What temp. are you using? You will be getting 'scum' all the way through to process to some extent.

[Zalbar]

Don't think you're doing anything wrong. The only thing I can think of is that your temperature is too low.

You can review the following 5 videos:

http://www.youtube.com/watch?v=GrSpTr...

[docfood]

great videos, thanks