Witbier

There are similarities. Both are top-fermented wheat beers with plenty of carbonation, and according to the BJCP the balance of witbier resembles that of a weissbier.

That is where it ends. The grain of witbier consists of 30–60% unmalted wheat, sometimes with some oats, and it is spiced with coriander and dried orange peel. The BJCP explicitly says that the spiciness and citrus of witbier come more from those additions than from the yeast. In weizen at least half of the grain is malted wheat, and it owes its banana and clove to a special weizen yeast; no spices go in. A scientific article on wheat beer also makes that distinction: malted wheat in German weissbier, unmalted wheat in Belgian witbier.

The origin differs too: witbier comes from Brabant (including Leuven and Hoegaarden), weizen from Bavaria.

The BJCP calls coriander seed and dried orange peel 'traditional' in witbier. That is right for witbier as we know it now. The obituary of Pierre Celis in the trade journal Brauwelt describes his beer as spiced with coriander and orange peel. The Brewers Association writes that witbier has been brewed 'since the 1960s' with coriander and orange peel.

The historian Roel Mulder, however, who works with 18th- and 19th-century brewing sources, states that those spices are missing in the old Belgian witbier recipes. They are also missing in the version of Louis Tomsin, the last witbier brewer of Hoegaarden, who stopped in 1957. The old witbier consisted mainly of pale wind malt, unmalted wheat and oats, and in Hoegaarden was even fermented spontaneously.

'Traditional' in the style guides is therefore about the tradition since the revival by Celis in 1966, not about the witbier of the 18th or 19th century. When spices first turned up in witbier has not been established.

With bottle refermentation, some sugar or wort is added to the beer at bottling. The yeast then makes the carbon dioxide in the bottle. The BJCP calls bottle refermentation a common characteristic of the Belgian monastic beer styles, and under the HORAL rules Oude Geuze and Oude Kriek must referment in the bottle. That yeast then sinks to the bottom is normal. A guide from CraftBeer.com (Brewers Association) even recommends storing speciality beer upright, so that the yeast sinks to the bottom.

Whether you pour the layer along differs per style. With weizen the brewer may, according to the BJCP, indicate whether the yeast should be swirled up. Australian Sparkling Ale is, according to the BJCP, usually poured with the yeast. Witbier is, according to the Brewers Association, traditionally poured cloudy. With tripel the BA, on the contrary, writes that you are not supposed to swirl up the yeast on purpose.

One caveat. Contamination with wild yeasts or bacteria can, according to the Brewers Association, cause cloudiness and flakes, and in addition off-aromas and off-flavours, sourness or a bottle that foams over when opened ('gushing'). But in a beer that has been refermented in the bottle, a layer of yeast at the bottom is not in itself a sign of spoilage.