Brewing tables from 1867-1871.

In the book "Die Gährungschemie" from 1854, written by Carl Balling, it says that Bavarian legislation implemented in may of 1825 proscribed no more than 7 eimer of winterbier and no more than 6 eimer of sommerbier from a scheffel of malt, and that 3 pfund of hops were to be used for the winterbier, and 5 pfund for the sommerbier. In other words, the law of 1825 reverted legislation back to the stipulations of the regulativ of 1811. According to Balling then, this was the law of the land in 1854.

In the book "Handbuch für Bierbrauer" also published in 1854, and written by a brewmaster named Müller, the author describes the brewing methods for schenk, lager, bock and salvatorbier. According to him the bockbier tastes more sweet than bitter, is more lightly hopped compared with the regular Bavarian lager beer and also somewhat darker in color. 4.5-5 eimer of bock are made from one scheffel of malt, and 2-2.12 pfund of the finest Bohemian hops are used. The bock is brewed in december-january and served in May, since, as per Bavarian law sommerbier and bockbier could not be served before May first.

Salvatorbier according to Müller has a darkbrown color, little carbonation due to it usually not being bunged, and has a hop-bitter after taste. Only 4, or no more than 4.5 eimer of Salvator are made from one scheffel of malt, and 3 pfund of the finest Saazer hops are used. Salvatorbier is also brewed in december or the beginning of january and lagered for 2.5-3 months before being served.

For regular lagerbier, or sommerbier, the numbers are the same as those for the 1811 regulativ as far as malt goes. On hops he says that for breweries with good cellars, 4-5 pfund of good quality new hops per scheffel of malt are used for beer meant for the first four months (may-august). For beer meant to keep until september-october 6-7 pfund are used.

Some calculations made from the numbers above:

Bock 5 eimer =320 liter, 2.12 pfund hops =1187.2 gram divided by 3.2 hl =371 gram per hl
Bock 4.5 eimer = 288 liter, 2.12 pfund hops = 1187 gram divided by 2.88 hl= 412 gram per hl

Salvatorbier 4.5 eimer = 288 liter, 3 pfund hops = 1680 gram divided by 2.88 hl = 583 gram per hl
Salvatorbier 4 eimer = 256 liter, 3 pfund hops = 1680 gram divided by 2.56 hl =656 gram per hl

Lagerbier 6 eimer = 384 liter, 4 pfund hops = 2240 gram divided by 3.84 hl = 583 gram per hl
Lagerbier 6 eimer = 384 liter, 5 pfund hops = 2800 gram divided by 3.84 hl = 729 gram per hl
Lagerbier 6 eimer = 384 liter, 6 pfund hops = 3360 gram divided by 3.84 hl = 875 gram per hl
Lagerbier 6 eimer = 384 liter, 7 pfund hops = 3920 gram divided by 3.84 hl = 1020 gram per hl

What these numbers would have meant for the actual beer is of course open for speculation. With the lower original gravity of lagerbier vs salvatorbier or doppelbier, yet a higher hop addition, would this have resulted in a more bitter beer than we nowadays associate with Bavarian lager beer? My personal opinion, based on what I've read, is that this was the case. The schenkbier or winterbier provided a sweet, low attenuated beer which used old hops in lower quantities that didn't produce a strong bitterness. It wasn't required to be stored for long and the colder winter weather helped to protect the beer. The lagerbier or sommerbier was a bitter albeit a similarly low attenuated beer of a slightly higher original gravity using hops from the latest harvest in higher quantities for their preservative properties, and the effect that this had on the flavor of the beer was appreciated by some people, and disliked by others (not unlike today).

The sommerbier was stored for much longer than the winterbier so a certain loss of bitterness would have occurred over time (although it would be stored at below fridge temperatures during lagering), but if we use the pilsener lagerbier as a measuring stick, and we suppose that this beer wasn't merely 30 IBUs like a modern German pilsner, but 40 IBUs at least (recalling a previous forum discussion on this issue), I would think that it is safe to say that we could assume at least an IBU of maybe 50-55 for a sommerbier of a gravity similar to a modern day export or festbier, around 12.2-13.7% original gravity, albeit with a lower abv (around 4-4.8% abv) due to a lower degree of attenuation.

That would be my thesis at least. I'm interested in hearing other peoples opinions and perspectives on this issue however.

 

Here's a table of Munich beers analysed in 1866 which might be of some interest in the context of this thread.

Hofbräuhaus Bock
Abv: 6.35%
Calculated stammwürze: 17.99%

Hofbräuhaus Sommerbier
Abv: 4.85%
Calculated stammwürze: 12.69%

Hofbräuhaus Weissbier (top-fermented weizenbier)
Abv: 4.38%
Calculated stammwürze: 11.75%

Hofbräuhaus Weisses Bockbier (top-fermented weizenbier)
Abv: 5.5%
Calculated stammwürze: 13.37%

Spaten Bockbier
Abv: 6.5%
Calculated stammwürze: 18.96%

Zacherl Salvatorbier
Abv: 5.6%
Calculated stammwürze: 18.61%

Löwenbräu Winterbier
Abv: 3.75%
Calculated stammwürze: 11.92%

 

I found another couple of tables which have some interesting numbers, namely two records of brewing materials used for royal Bavarian breweries.



Schleissheim Sommerbier 1818-19
322 scheffel malt
1458 pfund hops 816480 gram
2485 eimer beer 168980 liter 1689.8 hl
7 eimer per scheffel malt
483 gram per hl

Schleissheim Sommerbier 1819-20
378 scheffel malt
2062 pfund hops 1154720 gram
2664 eimer 1811.52 hl
7 eimer per scheffel malt
637.4 gram per hl

Schleissheim Sommerbier 1820-21
392 scheffel malt
1901 pfund hops 1064560 gram
2900 eimer 1972 hl
7 eimer per scheffel malt
539 gram per hl

Schleissheim Sommerbier 1821-22
406 scheffel
1980 pfund 1108800 gram
2938 eimer 1997.84
7 eimer per scheffel malt
554.9 gram per hl


Five royal brewhouses: Hofmühle bei Eichstädt, Hirschberg, Titting, Burheim, Welheim

Lagerbier 1806-07
18904 metzen malt (1 scheffel = 6 metzen)
17380 pfund hops 9732800 gram
15732 eimer lagerbier 10697.76 hl
4.9 eimer of beer per scheffel of malt
909.7 gram per hl

Put another way, the Schleissheim sommerbier used on average
483 gram per hl in 1818-19
637 gram per hl in 1819-20
539 gram per hl in 1820-21
554 gram per hl in 1821-22

Worth noting is that Schleissheim brewed on average some 7 eimer of sommerbier per scheffel of malt, since the law of 1814 was in effect during these years.

The five royal brewhouses brewed on average 4.9 eimer of lagerbier from one scheffel of malt in 1806-07 (i.e pre-1811 regulativ), similar to the Munich bockbier described by Müller, so the wort strenght might have been comparable to it (Müller says that the extract content by saccharometer was 15.5-16.5% for Bock, in contrast with Salvatorbier which according to him was 17.5-18.5%). So perhaps the sommerbier of the five royal brewhouses was similar to the lower end of Bock strenght, around 15%, whilst containing more hops due to being brewed to be sommerbier.

 

For comparative purposes I could submit some numbers from a Swedish governmental report on the domestic beer industry from 1923, which contains information from the Swedish brewers association as it pertains the malt and hop use for different types of beer. It says that for one hl of beer these amounts of ingredients are used:

Porter
Malt: 35.2 kg
Hops: 1200 grams
Lager beer
Malt: 22.8 kg
Hops: 197 grams
Pilsner beer
Malt: 21.1 kg
Hops: 441 grams
Svagdricka (top fermented small beer, no more than 6% plato)
Malt: 9.9kg
Hops: 80 grams

The amount of hops for Swedish pilsner beer is not that far removed from the 1906 Pilsener Lagerbier. The Swedish lager beer on the other hand used less than half the amount of hops on average compared with the Swedish pilsner beer. It was noted in the late 1800s by the Swedish brewers association themselves that the Swedish lager beer was less hopped than the Bavarian lager beer. However when Bavarian lager beer was first introduced in Sweden in 1843, the brewery in question advertised that they had "Bavaria's most bitter type of beer, the Nürnberger beer" for sale, and they later offered Bavarian beer, bitter and less bitter for sale.

I don't have any numbers for Swedish beer brewing back then, so it's impossible to say how those beers related to the Bavarian originals or to the Swedish lager beer of the early 1900s. But it would seem to me as if Swedish lager beer brewing, by the 1900s, combined the higher wort strenghts of Bavarian sommerbier with the light hoppiness of Bavarian schenkbier, and it would seem as if a similar process took place in Bavaria itself, generating the beer styles we now know as dunkel and märzen. Both the dunkel and amber märzen style of today might be described as a combination of the higher wort strenghts of sommer/lagerbier, with the shorter lagering times and lower hop additions that characterized the winter/schenkbier.

 

It is interesting I think to consider how the Pilsener Lagerbier related to the Bavarian lagerbier. In Bavaria sommerbier was also known as lagerbier. The lagerbier was characterized by a higher wort strenght than winterbier, longer storage times and larger hop additions of Bohemian town-hops (of which Saazer hops were held to be the best) from the latest harvest. This was proscribed already in the 1811 regulativ. Once Bürgerliches Brauhaus starts brewing bottom fermented beer around 1842, with the help of a Bavarian brewmaster, Josef Groll, what they brew is Lagerbier from Pilsen, or Pilsener Lagerbier. They didn't have to look very far for inspiration as it pertained the use of Bohemian hops, Josef Groll would have been familiar with the 1811 regulativ (in effect again by 1825, Groll was born in 1813) which proscribed even larger additions of Bohemian hops than what was used for the 1906 Pilsener Lagerbier.

The way I see it, Pilsener Lagerbier was inspired by Bavarian lagerbier (sommerbier), not only as it pertained the bottom fermentation and lagering, but also the hop addition, the kind of hops used and the amounts used. Pilsener Lagerbier was a golden version of the Bavarian Lagerbier/Sommerbier braunbier, a type of beer which more or less disappeared in its native Bavaria.

The reasons for this are probably plentiful and complex, but from what I've read there were alot of changes taking place in Bavarian beer legislation in the second half of the 1800s. In 1850 the law against brewing in the summer months was abolished and in the late 1860s the biersatz, which had regulated the brewing of beer, was beginning to become abolished. Add to this artificial refridgeration and now a brewer could brew beer at whichever strenght he wanted, whenever he wanted, using as little or as much hops as he wanted, and be guaranteed a sound end-result.

 

I found a book, Amerikanische Reise-Skizzen aus dem Gebiete der Technik: Landwirthschaft und des socialen Lebens (American travel sketches from the technical field: agriculture and the social life) published in 1867, written by a Ludwig Häcker from Austria-Hungary who spent a year travelling across the US in 1863-1864 visiting various cities and breweries, and in the book he describes his travels as well as the brewing practises of American bottom and top fermenting breweries (including the use of corn, rice and other adjuncts). Of bottom fermenting breweries he says "The hop addition for Schank beers amounts to a mere 1/2 to 1 pfund per barrel, for lager beers according to prevailing circumstances up to 3 pfunds." (page 162). For top fermented beers he says that the hop addition for common beer and pale ale amounts to 1-3 pfund per barrel. Common beer has an original gravity of 11-13%, pale ale 12-14%, stock ale 14% and above (page 172).

According to the conversion table found on page 199, one barrel is equal to 137.6 liters. One pfund is equal to 453 gram. 1 pfund is thus 453 grams, half a pfund is 226.5 gram, 3 pfund 1359 gram. One barrel contains 1.376 HL. 453 gram divided by 1.376 is 329 gram per HL. 226.5 gram becomes 164.6 gram per HL. 1359 becomes 987 gram per HL.

So the range for American Schank beers was 164.6-329 grams of hops per HL according to Häcker, whilst Lager beer had a higher hopping rate, with a maximum of around 987 grams per HL.

It is interesting I think that Häcker divides the American bottom fermenting beers into schank and lager beer, using the terminology used in both Bavaria and Austria-Hungary at the time. It is also interesting that he finds a clear difference in hopping rates inbetween schank and lager beer, which was also the case in Bavaria. The relatively high maximum for lager beer, 987 grams per HL is interesting as it pertains to this thread. The range of hopping rates that this allows for would have made it possible for German-American lager beer brewers to live up to the Bavarian regulativ of 1811 and 1825.

 

It might be interesting to also consider what JC Jacobsen, the founder of Carlsberg wrote about his travels to Bürgerliches Brauhaus in Pilsen. According to Carlsberg the visit is likely to have taken place in 1874 as part of a larger tour of European breweries. In his notes he writes: "The wort held, it was said, 13% and what I tasted was said to have 5% (?) very bitter. Noback said that they used 100# of the finest Saazer, which the brewers themselves sought out bale for bale, for 100 eimer (in other words more than the double of what I use!)."

Noback might refer to the brewing engineer Gustav Noback who was a brewing engineer and brewmaster from Prague who had done work for alot of different breweries across Austria-Hungary (and beyond), including Bürgerliches Brauhaus in Pilsen. If the pounds thus are Wiener pounds of 560 grams each (same as the Bavarian pound), and the eimers are Wiener eimers of 61 liters each, the hundred pfunds for 100 eimers comes out to 918 grams of Saazer hops per HL for a wort of 13% stammwürze.

 

That would seem like the most logical explanation, although the question mark is found in Jacobsen's own notes.

I noted that in one of your (old) blog posts on sommer and winterbier you quote from a German lexicon from 1903 in which it says:

"Lagerbiers are Winterbier or Schenkbier, that is intended for early consumption, or Sommerbiers (Lagerbiers in the narrower sense) that are stored in special cellars until well into the summer and autumn. This difference was particularly true for Bavaria, as long as brewing only took place from October to April and from 1 hl of malt on average of 2.5 to 2.6 hl of Winterbier, but only 2 to 2.1 hl of Sommerbier was produced. The introduction of the refrigerator, which allows brewing in the summer, has blurred the differences more and more."

It would seem reasonable to me that the allowing of summertime brewing (in 1850), and artificial refridgeration impacted the Bavarian beers in various ways, one of which being the reduction in hopping rates for Lagerbier, or sommerbier, even though this particular aspect isn't mentioned in this excerpt. I find it curious though how this aspect of Bavarian lager beer brewing seems to have been forgotten about.

I can understand it though. From the perspective of English brewers, Bavarian brewing simply went from using comparatively little (in comparison with English brewing) hops to using even less hops. In countries outside of the German states on the other hand, the distinction between winter and sommerbier was never established in the first place (since there were no laws against brewing in the summer, and no bierregulativ proscribing ingredient amounts), or at least not maintained as a terminology. A beer which would have been labeled schankbier or winterbier in Bavaria could be called a lager beer in Sweden, Denmark, Norway, Finland, England or America (in Sweden for example a lower gravity type of bottom fermenting beer was introduced in the second half of the 19th century but instead of using the word schankbier for this type of beer the term "lagerdricka" was used, this term was derived from "lager beer" combined with the Swedish word dricka which to the Swedish public denoted a lower gravity beer, they essentially reinvented the wheel). Over time lager beer takes on the meaning of being the sweet and mildly hoppy brother of the hoppy and bitter Pilsener lager beer. "Pilsner" in turn becomes detached from its roots as a lagerbier and is transformed into something very different from it. Lastly, from the perspective of Bavarian brewers there was and is no real incentive for remembering something which doesn't fit with the narrative of Bavarian brewing adhering to centuries of tradition.

 

Been reading this book "Der Hopfen aller hopfenbauenden Länder der Erde als Braumaterial" (the hops of every hop growing country on earth as brewing material" by Richard Braungart, published in 1901. The main argument in the book is that the introduction of ice-cellars, ice-machines and artificial refridgeration had resulted in a substantial drop in hop use among Bavarian breweries (as well as among American breweries). Whereas previously the hops had been used as a preservative, along with storing the beer in cool cellars, the introduction of ice-cellars and ice-machines had eliminated the need for using large amounts of hops. The brewery could now have winter-like conditions all year round (and since the law against summer time brewing was abolished in 1850, brew year round). He says that the beer being produced by the large breweries in Munich is sweeter and not lagered for as long as the old lager beer.

He also opines that the growing popularity of pale Pilsener beers is a consequence of the lower hop additions and shorter lagering times of Bavarian beer. In other words, Pilsener beers offered that which the Bavarian lager beer used to offer but no longer did (similar to what I was suggesting in one of my posts above). I think this line of thinking makes alot of sense, of viewing Pilsener lager beer not as an historical accident or mystery, but instead as a continuation of a Bavarian tradition.

On page 445 he talks about the hopping rates for beer in Nürnberg 40-50 years ago, as told to him by a Nürnberger brewer. For Schenkbier they used about half a pfund of hops per hl. For lagerbier intended for april-may they used 1 pfund, for june-july 1.25 pfund, for july-august 1.5 pfund, for august-september 1.75 pfund. He says that in the country side where they have lower quality cellars they use up to 2 pfund for the last lager beer brewed. This also applied to Franken and Süd-Bayern. Braungart uses the zollpfund of 500 grams elsewhere so I take these pounds to be such pounds, which would make the hopping rates span between 500-875 grams per HL for Nürnberger lagerbier, and 500-1000 grams for country side lager beers.

On page 446 he says that the now deceased technologician Dr. Karl Reischauer said 30 years ago, that the amount of hops shifted alot but on average more than one pfund of hops were used per HL winterbier, and 1.5 pfund for lagerbier.

He goes on to say that as the ice-cellar installations have reached a high degree of development, these additions have been considerably reduced, by as much as ½ to two thirds, to where in the large breweries with the most modern equipment, a mere half a pound of hops is used on average per HL.
"As the ice-cellar installations reached a high degree of education, were these additions, which still alot of times consisted of the finest, most expensive hops, considerably reduced. Currently in the large breweries with the most modern brewing installations (ice-machines with cold-air conduction) is for the most part a mere half a pound used on average, in other words ½ to two thirds less."

He also provides a table with hopping rates for the various types of beers brewed in (then) contemporary Münich:




On page 447 he mentions the chemist Stockmeier according to whom, before the introduction of ice-cellars and ice-machines, in other words in the 1850s-1860s, they used 1 pound of hops per HL of lagerbier, and for lagerbier which was to keep for very long 1.5 pounds. By the 1880s, by which time ice-cellars had been improved upon greatly and ice-machines were being introduced, the amount of hops used had dropped by some 40%.

He goes on to say that it is primarily the large and most modernized breweries which have taken part in these reductions, the middle sized and the smaller breweries still use considerably larger amounts of hops.

If one looks at the table above one can see where the sweet taste of the Bavarian lager beer came from, especially if one compares the numbers against the 1906 Pilsener Lagerbier. Whereas the amounts for the old lagerbier spanned between 500-750 grams per HL, i.e matching or surpassing the Pilsener of the early 1900s, by the early 1900s the numbers for Munich lager beer ranged between 230-333 gram per HL.

On page 477 in the chapter on American beer brewing he quotes a Professor Vuylsteck in Löwen who says that for American beer around 200-300 grams of hops are used per HL, whereas in the past larger amounts were used, whereas previously, according to other sources, the amounts used were considerably higher. Braungart argues thusly that the introduction of ice-machines had resulted in a drop in hopping rates also in American beer.

I think it's a fascinating book and well worth a read for those who are able to.

 

Here's another table from the book, page 447, detailing among other things beer production and hop use for brewing in Bavaria in the years 1867-1876.

"One notices by comparing heading 2 and 7 that the beer production in Bavaria in this short time span has almost doubled, but the hop demand remains the same, it even dropped by 3000 zentner. If the hop demand had followed the growth in beer production, then the hop consumption in Bavaria for the year 1876 had to have been circa 160 000 zentner, instead of 85 000 zentner. In that time there were still no large ice-machines, since the first one was installed in the Spaten brewery in Munich in 1875. These large hop savings were due to the highly developed ice-cellars (which used) ice gathered in the winter time."

If one divides the amount of hops used in the year 1867 by the amount of beer produced, one gets the number of 565 grams of hops per HL beer. Doing the same calculation for the year 1876 generates the number of 340 grams of hops per HL beer.

 

With the table above in mind it might also be interesting to consider that the bierregulativ of 1811 was abolished in 1864.

Page 412:

"In the year 1811 came then lastly the regulation, which raised the amount of winterbier that could be brewed to 35 eimer and for sommerbier to 30 eimer, this last regulation was in effect until the repeal of the beer tax in 1864. From 5 scheffel of malt should 30 eimer sommerbier be brewed and with an addition of 25 pfund of hops, of the lighter winterbier should from 5 scheffel of malt 35 eimer beer be made, with 15 pfund hops."

So in 1850 the law against summer brewing is abolished but the bierregulativ remained in effect, then in 1863 the law which had dictated ingredient amounts was abolished as well. To this one can add the lifting of restrictions on the brewing of extract rich doppelbiere in 1848. As it pertains this last point Braungart writes (on page 445) that according to Professor Holzner the average original gravity of the dark lager and export beers in oberbayern and to some extent in other parts of Bavaria increased from 12.5% to 14% and 14.5% in the years 1865-1885. The original gravity of Kulmbacher beers had also increased over this timespan. The cause of this was the taste preferences of the consumer. Even though the malt tax was increased this didn't impact the gravities of the worts. The beers of today (talking about the early 1900s) are at least as strongly brewed as before the tax increase. Braungart writes that a change is only likely to take place if the consumers should once again prefer lighter beers.

This last point is interesting when one considers the table of Munich sommerbiere from 1866 where the gravities spanned between 12.2-13.7. When one looks at Braungart's table for early 1900s Munich beers one can see that the schenkbier being brewed is equal in gravity to the old Munich sommerbier, with the 1901 sommerbier inhabiting the upper end of the gravity band for 1866 sommerbiere and pushing the gravitities into 14% territory, with Märzenbier (i.e the last sommerbier to be brewed in the old days) being brewed to 15-16% (similar to the numbers for the 1901-1903 Oktoberfest Märzen beers).

In other words, the schenkbier became stronger gravity wise but remained mildly hopped, the sommerbier maintained its strenght gravity wise but became more mildly hopped. The Märzenbier became stronger gravity wise (enabled by the law of 1848, before which the 15-16% original gravity would have been limited to doppelbiere, such as Hofbräuhaus Bock) but substantially lower hopped. All three styles would have gained in sweetness from these developments, with the sommerbier (lagerbier) and Märzenbier (lagerbier) losing in bitterness.

 

Found a couple of non-German sources which in passing mention the above mentioned developments.

Here's an excerpt from an American book on hop growing from 1883:

Ale requires more hops than beer, and while there is more ale
manufactured in the United States than formerly, yet the great
increase has been almost altogether in the use of the " lager beer."
This has tended to require a less quantity of hops to the barrel,
than when ale was the leading drink. Again, before the great
improvement in ice-houses and cold-air machines, lager beer
brewers used to lay in a large supply, in the winter, of "stock"
lager, which required twice the amount of hops that is needed for
beer brewed in spring and summer. Now they lay in only so
much ''stock" lager as will help them through the summer, by
using it with fresh beer, and then brew all they possibly can in
the summer. This requires less capital, less risk, less malt, less
hops, and the people like this light, fresh, creamy beer better than
the old strong " stock " lager.
Thus it comes about that though we now use twice the beer in
the United States, that we did in 1875, we by no means use twice
the amount of hops. Again, as in this year, 1883, when hops are
extravagantly high, brewers will use hops more economically.
Thausing, (edited by Drs. Schwarz and Bauer, New York, 1882),
says:
" Leaving out of account the strongly hopped English beers,*
" and some very strong local beers, the amount of hops added to
" our modern beers varies between 44/100 pound to 1 87/100 pounds per
" hectoliter, and amounts, on an average 88/100 pound per hecto-
" liter."

Here's an excerpt from a Department of Agriculture report on hops from 1907:

The consumption of hops in Germany has undergone marked
changes during the last twenty years. The returns show that the
consumption per barrel of beer brewed has decreased from 0.95 of a
pound in 1880-1884 to 0.5 of a pound in 1900-1904.

Table from page 31:

 

I have been wondering for some time now about the origins of these higher gravity Oktoberfest Märzenbiers that were served at the 1901 and 1903 Oktoberfest, and which are found in Braungart's table. I've been coming across references in various books to the year 1872 when supposedly a Märzenbier was first served at the Oktoberfest, and thus replacing the old sommerbier. I had yet to find any more information about this shift, but it appears it's been right under my nose for some time. On Franziskaner's website in the history section they have this to say about the year 1872:

1872
Franziskaner auf dem Oktoberfest
Im Schottenhamel Festzelt auf dem Oktoberfest wird erstmals das von der Franziskaner-Leist-Brauerei erzeugte bernsteinfarbene Oktoberfestbier, das Ur-Märzen, ausgeschenkt. Es ist ein goldgelbes, nach Wiener Art gebrautes Bier, das stärker als das Sommerbier eingesotten wird.

"1872
Franziskaner at the Oktoberfest
In the Schottenhammel fest tent at the Oktoberfest is, for the first time, the amber colored Oktoberfest beer, the Ur-Märzen (original märzen) served, produced by the Franziskaner-Leist brewery. It is a golden-yellow, Vienna-style beer, which is brewed stronger than the summer beer."

So up until 1872 the beer served at the Oktoberfest (or at least the lager beer served) was sommerbier, of the type described throughout this thread. Then in 1872 a higher gravity beer, a golden-yellow/amber Wiener Märzen is introduced and called a Märzenbier, even though this term had existed previous to this as a synonym for the sommerbier.

Since then Franziskaner has been turned into a purely weissbier producing brewery (they first started brewing wheat beer in 1964), and Spaten has assumed the Ur-Märzen brand as their own.

 

From the Schottenhamel website:
IM HEISSEN SOMMER 1872 GESCHIEHT DAS UNFASSBARE:
Das für die Wiesn reservierte Lager- und Sommerbier ist vorzeitig aufgebraucht und Michael I. bringt ein neues Bier auf die Wiesn, das die Franziskaner-Leistbrauerei bereits im Monat März nach der Wiener Art gebraut hatte: Das Märzen. Das für die damalige Zeit helle Bier war mit 16 Prozent Stammwürze wesentlich stärker und auch teurer, wurde aber zum klassischen Oktoberfest-Bier.

In the warm summer of 1872 the unthinkable occurs:
The lager- and summer beer which was reserved for the Wiesn is prematurely depleted and Michael I brings a new beer onto the Wiesn, which the Franziskaner-Leistbrauerei had brewed already in March in the Vienna-style: the Märzen. The for its time pale beer was with 16 percent original gravity considerably stronger and also more expensive, however it became a classic Oktoberfest beer.