It comes from a very odd source: a report of a trip of British brewers to the Brewers' Exhibition in Berlin in 1908. It seems that on their way back, the party called in Cologne and visited a couple of breweries. The date is very important as it's about the time Kölsch first appreared.
This definitely sounds like a description of a Kölsch Brauhaus:
"On our arrival at Cologne, the friends who met us there informed us that they could not offer us the inspection of large breweries such as we should have soon in Berlin and other parts, but they had many small breweries, and, if of interest, they would arrange for us to look over any of them.Top-fermented, then lagered cold. That's spot on for Kölsch. 17 lbs per barrel is 1047º - which also sounds right for Kölsch. 100 barrels a week is around
We were taken to a small brewery, known as the Obergahriges Restaurant Brewery, which had been working about two years, and whose beers at the moment were exceedingly popular in the town. It was a large restaurant brewing its own beer; behind the restaurant was a model brewing plant, with everything nicely arranged, covering a space of 100 feet square; the whole plant had been erected at a cost of £2000.
The beer was produced on the top-fermenting system: it was fermented for four days, then run into the lagers and stored for eight weeks, afterwards chilled and filtered, and served up in the usual way. Its gravity was 17 lb., and we again noticed the pronounced hop flavour which finds such ready appreciation with Germans. The whole of the brewery production was sold in the restaurant (at the time of our visit, about 12.30 in the day, we found 200 customers there), and, as far as I could ascertain, their trade was not less than 100 English barrels per week, to us a large and remarkable trade for one restaurant. We were told, much to our surprise, that the majority of the restaurants brewed their own beer."
Journal of the Institute of Brewing, Volume 14, Issue 1, January-February 1908, pages 50-51.
Note how the restaurant had only been open two years. Bang on when Kölsch was born. Just a shame he didn't tell us its real name. Obergahriges Restaurant Brewery is clearly just a description of what the place was, not its actual name.
Thankfully, there's a description of how the beer tasted: "pronounced hop flavour". Sounds to me that Kölsch was definitely bitterer back then.
Strange that the author should be so surprised at restaurants brewing their own beer when there were still thousands of British pubs that brewed. In 1912 there were 2,663 publican brewers*.
The other brewery sounds particularly odd:
"We also visited a still smaller brewery, connected with a small restaurant resembling the home brewery attached to the licensed house, frequently found in this country. The proprietor informed us that he was only able to brew during the winter months, but he brewed sufficient then to carry him through the summer. In his case he brewed with bottom-yeast, and he was able to carry through his fermentation successfully at about 50° F. When the beer had gone through its course of fermentation, it was filled into lagers of 12 to 15 English barrel capacity, and removed to the town cellars, where large quantities of beer were stored for small brewers, and the casks were taken out one at a time as required.I'm very surprised that a small pub brewery was using bottom-fermenting yeast. Especially with the relatively high fermentation temperature of 50º F. And didn't Cologne have a Reinheitsgebot that forbad bottom fermentation?
It will be noticed that the small brewer was maturing his lager at cellar temperature, viz., 52° (a high temperature in comparison with the large breweries), and I was astonished to find he was able to do without an expensive ice plant, and still produce a beer which I considered equal to any lager I had tasted; it had the pronounced hop flavour, and was very pleasant and refreshing, although perhaps a little too bitter. His trade, he informed me, was from 10 to 15 barrels per week. This was also the only case where I found the boiling of wort done by fire in place of steam."
Journal of the Institute of Brewing, Volume 14, Issue 1, January-February 1908, page 51.
I'd never heard of beer being stored in town cellars in Cologne. I wonder when that died out?
If a British brewer complained about a beer being too bitter, it must have been damned bitter. All British beers were hopped like crazy before WW I. I would claim this as more proof of Kölsch once being bitterer, except this obviously wasn't a Kölsch, being bottom-fermented. What would you call this beer? A Lager?
* 1928 Brewers' Almanack, page 118.