When to use Crystal malt?

When designing a recipe, when should I include crystal malt? What does it contribute?

Beer Smith says it adds body and improves head retention. I designed a hefeweizen / IPA hybrid, bought the grains from my LHBS, and when he was ringing up my bill based on my grain listing he said "Huh, Caramel?..."... as though it was a strange addition. I just used 0.5lbs of 10L. I'm still pretty green at this... perhaps it's strange to add body to a wheat? I'm not sure why I added it, it just seemed like an easy way to add complexity.

My next recipe may be an American Brown, and Designing Great Beers says about 66% of browns include crystal. It'd be nice to know the reasoning behind using it vs. not.

Thanks!

It's not just to add body. If that's what you're after, then use Carapils or other dextrin malts/powder. Crystal/Caramel also adds sweetness and unfermentable sugars, not to mention caramel flavors. Styles like hefeweizen traditionally have no crystal. English beers and American styles that sprang from them usually contain crystal of some amount.

Just know that as the ºL goes up, so does the sweet to caramel, toffee raisin, plum, fig flavors as well as the unfermentability.

10ºL = Sweet
20ºL = Light Caramel
40ºL = Caramel
60ºL = Dark Caramel/Toffee, some fruit
80ºL = Slight burnt toffee, raisin,
120ºL = Raisin, fig, plum, deep toffee
150ºL = Burnt raisin, fig/plum almost burnt sugar

Thanks Brewsmith! This was exactly what I was looking for. Hopefully it doesn't end up making my beer too sweet, though my inspiration beer (Lagunitas Lil Sumpin Sumpin Hoppy Wheat) did have some sweetness. We'll see!

The guy at the store probably thought you were making a straigt Hef which is why he commented. Since you are doing a Hef/IPA hybrid, the crystal is appropriate.

Interested in how this turned out; I've been trying to hit something close to the Li'l Sumpin Sumpin through 4 batches now. Problem is I haven't been able to get it to remind myself what its like for months. What was the recipe? How'd it turn out?