One system that is very particular to contemporary Czech beer is its categorization. Beers are mainly categorized in two dimensions, colour and strength.
The three main types of colour are světlé (pale), polotmavé (semi-dark), and tmavé (dark) or černé (black). The four types of strength are lehké (light beer at < 8°P), výčepní (draught beer >= 8°P and <11 °P), ležák (lager beer >= 11°P and <13°P) and speciál (specialty beer >= 13°P). Put in a matrix, you’d theoretically end up with 12 different types of beer.
From what Evan Rail told me, a lot of Czech breweries keep to a particular scheme: whereas the draught and lager beer at 10° and 12° would be typically pale, a 13° would often be semi-dark and a 14° would be dark or black. While there are certainly exceptions to it (Kozel Černý with its 10° comes to mind), it’s apparently something a lot of breweries stick to.
In my research, I have now found evidence that this practice may reach back well into the late 19th century. The book Die Malz- und Bierbereitung by E. Leyser, published in 1900, contains a whole section on Austrian brewing practices. At that time, the Austrian-Hungarian empire was still around, so Austrian brewing practices didn’t just cover what’s modern Austria, the small, mostly German-speaking country in Central Europe, but also those of the other Austrian crown lands, of which the most important one for beer brewing was Bohemia, a part of what’s the Czech Republic nowadays.
About the topic what beers are being brewed there, Leyser writes “In Bohemian and generally Austrian breweries, four types of beer are usually brewed: Abzugbier, Lagerbier, Exportbier und Märzenbier. Lager- and Exportbier are beers of the Pilsner type, Abzugbier is in its properties located between Pilsner and Vienna beer, and Märzenbier can be seen as a specialty beer which in its character turns out to be similar to Bavarian beers.”
Later, he describes which malts are used for these beers: “The kilning temperature of malt for Abzugbier is about 64°R [80°C], for Lager- and Exportbier 48°R [60°C] and for Märzen 72°R [90°C] resp. 77 to 80°R [96-100°C]. For Märzenbier, colouring malt is optionally used.”
To put this in context, we can correlate these temperature ranges with the typical kilning temperatures that the book mentions earlier on: 40 to 55°R for Bohemian malt and 60 to 70°R for Vienna malt. Unfortunately, Leyser mentions no particular kilning temperatures for Bavarian malts. But for that, we can use another source, Julius Thausing’s “Theorie und Praxis der Malzbereitung und Bierfabrikation” from 1888. It contains kilning temperatures for various malts, 45 to 60°R for Bohemian malt, 60-70°R for Vienna malt, and 65 to 80°R for Bavarian malt. This gives us a good impression what the colour of the different beers most likely would have been: Abzugbier had a colour like Vienna lager, but probably on the lighter side of it, while Lager- and Exportbier were golden beers. Märzen though must have been darker, probably a light brown, or even going into very dark or even black, in particular if colouring (roasted malt) was used.
What we now still need is some information on the particular strength of these beers. Leyser gives us quite a bit of information. In an example, it lists Abzugbier at 10.3°B (Balling, the direct predecessor of Plato), Lager at 11.3°B, Export at 12.3°B, and two different Märzen at 13°B and 14°B. With that, we get the impression of portfolio that roughly matches the common portfolio of beers from Czech breweries I described earlier: the lowest strength one, Abzugbier, was a pale-ish beer, somewhere between Pilsner and Vienna lager, while 11 and 12° beers were pale, Pilsner-type beers. The specialty beers, called Märzen, at 13 and 14°, were definitely darker, probably ranging from a pale brown to outright black when brewed with roasted malt.
While not explicitly stated, my interpretation of this is that one of the two Märzen was probably darker than the one. At least this would very much fit the differentiation of 13° polotmavý and 14° tmavý/černý.
This scheme wasn’t necessarily kept by all breweries in Austria. Leyser describes his observations made at “brewery B. in Austria”, which brewed a Viennese-style Schankbier at 11.5°B, a pale lager at 12.5°B, a Viennese-style Export-Lager at 13.5°B, a Märzen at 14.5°B and a Bock at 15.5°B. Unfortunately, we don’t learn anything about the colour of Märzen and Bock.
Nevertheless, it was refreshing to see a very systematic approach at categorizing beer like we know it from Czech brewing to be already used in the year 1900 or before, which is something that got lost in modern Austrian brewing since then, not least due to the fact that Vienna-style beers as well as dark lager beers have been mostly neglected (the modern Austrian equivalent of tmavý is often sickly sweet and almost undrinkable) and only recently have had a comeback of some sorts.