I would like to crochet a shawl, but do not want to use the recommended yarn. The yarn I would prefer to use is one of the boucle yarns. Do I have to make any adjustments to account for the knobbiness of this yarn? Please advise. Thank you.
Hmm... good question. I generally don't recommend crocheting with a yarn that is too knobby, but if it is just a little and you don't run into problems working with it, then give it a try.
It's best if you can test it out first. Just do a little swatch in the stitch pattern that will be called for in the pattern. The issues I have with boucle are:
-- you may not be able to see where to place each stitch because the boucle makes it hard to see distinct stitches
-- the boucle may have big loopy parts in the yarn that cause your crochet hook to get caught and slow you down or create other problems
-- the boucle yarn will product a different gauge because the boucle part will create more fabric where a "normal" yarn would not
This swatch really is your gauge swatch, which you should do just to be sure the yarn will work to your satisfaction.
One note is that if this pattern is one where you will mostly be working stitches into arches or spaces, then the boucle effect might be just fine. Here is an example of a shawl pattern that works just fine with any kind of yarn because the crocheting is all done in the big spaces.