Like stated above, my definition of vorlaufing is "return the chunks."
I tend to do high-gravity beers. (that's a different story).
Needless to say, the first runnings are pretty damn syrupy/thick looking. It tends to look more opalescent or cloudy, IMO.
The first runnings are NOT translucent or clear.
The second (or third) runnings tend to be a lot more clear looking (like a hefeweizen or brownish ale).