Using wort to prime for bottling?

Ive read about using wort to prime for bottling, in Papazian's book.  How common is this? I'm trying it in my Raspberry Wheat Ale.

In the reviews section, I posted about the German wheat Beer book by Eric Warner. That book contains recipes that use SPEISE (wort) that has been saved unpitched. There are pointers and formulas in the book about priming with speise to achieve desired carbonation. I did make one batch that way. It is tricky as you don't want to save your unfermented wort too long or it may spoil. Wheat beer yeast takes only 3 days to finish so it works good, and speise and lager yeast are then added for priming. Sorry I've forgotten the details and dont have the book handy. Just raise the S.G. with enough speise to what you would have using sugar, but the trick is in calculating how much you need to save before hand, when the wort is fresh.. about a quart or 2..


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