know your yeast

I have learned what seems like a fairly obvious lesson: Before using an unfamilar yeast one should research its characteristics! Such confusion and annoyance I'd have been spared if only I'd looked at the Wyeast Labs web page for the 3944 Belgian Witbier strain before brewing my witbier:

Produces a complex flavor profile with a spicy phenolic character and low ester production. Phenols tend to dominate other flavors and dissipate with age. Ferments fairly dry with a finish that compliments [sic] malted and unmalted wheat and oats. Sometimes used in conjunction with lactic acid bacteria to produces a sharper finish. This strain is a true top cropping yeast requiring full fermenter headspace.

Flocculation: Medium-Low
Attenuation: 72-76%
Temperature Range: 62-75F, 16-24C
Alcohol Tolerance: 12% ABV

I was unfamiliar with the term top cropping. Ale yeasts are generally top-fermenting, but as fermentation diminishes the krausen breaks down and the yeast drops to the bottom of the fermenter. A top-cropping yeast does the opposite, with the krausen growing as fermentation subsides and the yeast rises to the surface. http://hbd.org/uchima/yeastzone/topcrop.html is informative, with good photos, and the recommendation that the fermenter be agitated once or twice a day in order to maintain the desired pace of fermentation.

This is exactly what had been puzzling me about the witbier (which is again fairly busy after racking to the secondary) and now it makes perfect sense. This is the first low flocculation yeast I have used, so that aspect of its behavior was also unfamiliar.

Silly homebrewer. Never again will I use a yeast without doing some research.