"Berliner Weissbier, that is now made from a mixture of wheat and barley malt in the proportion of 2 or 3 to 1. Mashing method: either decoction or infusion. Characteristic is not boiling the wort, to retain the typical Weissbier taste and to allow the use of a high-attenuating yeast mixed with long lactic acid bacteria. Since the wort is not boiled with the hops, these must be added to the wort in a different way. It mostly happens that, before mashing, the hops, per Zentner [100 kg] of grist 0,75 to 1 pound [500 gm] of hops, are added to the simmering water in the mash tun and so are boiled. The hops are present during the whole mashing process and end up with the spent grains in the lauter tun and so act as a goof filter for the wort. To better extract sugars from the spent grains, almost boiling water is used, which is possible in this case, since the final mash pumping temperature is not higher than 80 to 82º C and the filtered wort still contains a large amount of diastase, so there is no danger of starch haze. The hot wort is quickly cooled after lautering (cool ship, cooler) and pitched with yeast in large steel tanks at 13 to 20º C. The amount5 of yeast is 1 litre per 5 hl wort. After 8 to 12 hoursthe wort is transferred into smaller vats. The increasingly vigorous fermentation creates a covering of a mixture of hop resin, protein, wheat fat, that is black in colour: "pitch barm"; it is crafully skimmed off. Later the spent hops appear. The complete yeast layer remains until the end of the primary fermentation and is only removed when the wort is pumped out. The fermentation lasts five days.
After the end of the tun fermentation the beer is pumped into a collecting vat, from which together with fresh beer from the pitching vessel it is drawn off into smaller packages, bottles or stone jugs. It is worth mentioning that this mixture of finished and fresh beer contains between 10 and 35% water, depending on the wishes of the consumer. Hence the designation "half beer" as opposed to "full Weisse" or "whole Weisse", beer without added water.
An exception, approximately like Bock or Salvator in bottom-fermenting beers, amongst Weissbiers is formed by "Märzen-Bier", which because of its wine-like flavour is very highly regarded.
Original gravity 12 to 14 to 16% [Balling]. This beer conditions in the bottle without the addition of water. It takes months before the beer is ready to be consumed. Often the custom still prevails of burying the bottles in sand or earth to keep them at a constant cool temperature."
I find most interesting the fact that the beer was usually watered down just before packaging. I've not heard of that practice before. It's confirmed by "Die Bierbrauerei in der Neuzeit" by E. Zimmermann, published in 1913 (page297): "Before filling, kräusen (up to 30%) and often some water, too, are added to Berliner Weissbier." Also Schönfeld mentions the addition of 10 to 35% water in "Die Herstellung Obergähriger Biere", 1902, page 84: "
I had heard that stronger versions of Berliner Weisse had once existed, but this is the first real evidence. The gravities quoted are Lagerbier (12º), Märzen (14º) and Bock (16º) strength.
Mashing with the hops is a bit weird, too. But I suppose without a boil, you have few options.
"Die Herstellung Obergähriger Biere" has a whole chapter on Berliner Weisse. When I have time I'll try to translate at least some of that.