A short history of Koyt beer,

Koyt beer is a type of beer made with hops and oat-, barley- and wheat-malt in proportion generally of 3-2-1 respectively. It was around in the Low Countries at least from the end of the 14th - until early 17th century and was the main type of beer during a long time of this period. Contemporary historians think Koyt was inspired by the ‘new’ Hamburg beer that was introduced in 1374 as a successor of 'Rotbier' that had spread from Bremen to various other port cities.

Exporting beer
Koyt became an industry with a very big audience. Specialized Koyt brewers and city governments tried to ensure the quality of their beer. Gouda and Haarlem were true exporters but there were others and the old Hanseatic cities brewed Koyt for their own sphere like Zutphen (3).

Quality
The heyday of Koyt beer was in the 15th century with large exports, particularly to present-day Belgium. One of the highlights was the beer riot in Leeuwarden (4) where people literally rebelled when they where blocked from drinking their Koyt. From 1433 we see the emergence of 'Double Koyte' and from then one had to watch out what kind of Koyt you got. Koyt was getting thinner with increasing grain prices. In Antwerp Koyt and Knol remained the normal beer well into the 17th century. Especially in the 18th century we often find a devaluated Koyt equal to 'Thinbeer'.

Lost brewing oats
Brewing oats were a special oat-type with more starch and probably less beta-glucans; a thicker and heavier oat-type. It was still mentioned by Lacambre in 1851: ’mais les avoines de bonne qualité dites Avoines de brasseur pèsent de 49 à 51 kilog. l'hectolitre’. In the course of the 19th century this oat-type was replaced by oats with a larger yield that were far less suited for brewing. There was less diversity in brewing and this was at last almost exclusively done with barley.

Lost recipe
Late 18th century, there's still Koyt in Zwolle in 1790: 'even today in the summertime there is a very thin and also very tasty white beer being brewed under this designation'.
Mid 18th century, Koyt beer was still seen in the county of the Marck. In Hamm, the capital, they had amazing gammon, in Holland called 'hammen'. Although somewhere in time the old recipes for making Koyt where lost or changed the Koyt (Hammer Keut) is transported 'far & wide', and is apparently still alive and well, as if time had stood still.

Frederik Ruis

I wrote about the confusion over hopped or unhopped Koyt beer early 2012.

An article about the kind of oats used in Koyt beer.

(1a)
Geschiedenis der heeren en Beschrijving der stad van der Goude.
Meest uit oorspronkelijke stukken bij een verzameld door
Cornelis J. de Lange van Wijngaerden
Tweede deel (Google eBoek)
Van Cleef,
1817

p.377
en geen ander kruid als hop

[In the year 1520 it was granted... ...and no herb except hops]

(1b)
The name is found in various Low German, Dutch and/or Saxon dialects that differ slightly from region to region and vary through time; kuit, koeuten, koeuts, koyten, koyte, keuts, coyten, kuiten, coeijt, koeuten-breuwer, kute, kuite, keut, koite, keuit, kuyt.

(1c)
Groot algemeen historisch, geographisch, genealogisch, en oordeelkundig woordenboek, behelzende zo het voornaamste, dat vervat is in de woorden-boeken van Morery, Bayle, Buddeus, enz...
(Google eBoek)
Brunel,
1729

p.169
1455 Goudsche Kuyt

Hertog Philips van Burgundië vergunde in 't jaar 1455 ten voordele der Goudsche brouwers, dat de hop-accyns op een broudsel...

[Duke Philip of Burgundy licensed, in the year 1455, in favor of Goudsche brewers, the hop-accyns on one brew ...]

Keizer Maximiliaan, en Karel, hertog van Oostenryk, verleenden den Goudsche brouwers in't jaar 1508, dat ze hunne bieren in Brabandt, Vlaanderen, Hollandt, Zeelandt, en Vrieslandt tot hun believen en goedvinden zouden mogen voeren en verkopen, zonder dat de wethouders of ingezetene der zelve landen, onder voorwendsel van eenige octrooien, of anderszins, de Goudsche bieren zouden mogen bezwaren...

[Emperor Maximilian, and Charles, Duke of Oostenryk, granted the brewers of Gouda in the year 1508, they could sent their beers to Brabandt, Flanders, Hollandt, Zeelandt, and Friesland to sell if it pleased them, without the aldermen or residents of these countries themselves, under the pretext of some patents, or otherwise, were allowed taxes on the Gouda beer...]

(1d)
Jaarboek voor Middeleeuwse Geschiedenis 13
Leen Alberts
Uitgeverij Verloren
2011

Bier drinken met maten

p.139
De typenaam kuitbier werd door zijn overheersende verkrijgbaarheid weinig gebruikt.

[The type name Koyt was little used because of its predominant availability]

(2a)
De gilden van Utrecht tot 1528
Verzameling van rechtsbronnen
uitgegeven door Mrs. J.C. Overvoorde en J.G.Ch. Joosting.
Tweede deel
's Gravenhage,
Martinus Nijhoff
1896

1397

p.106
1397, Augustus 17 (Verbod van fraude.)
1. Wie koeyt tappede voer Hamborger bier, die verboerde V ?, also dicke alst yemand dede.
2. Ende wie koeyt tapt, die en zel gheen Hamborgher tappen, bi denzelven koer voerscreven.

[1397, August 17 (Prohibition of fraud.)
1. He who sells koyt instead of Hamburg beer, will be sanctioned …
2. And who sells koyt, shall not sell Hamburg beer]

(2b)
Geschiedenis der Heeren en beschrijving der stad van der Goude
meest uit oorspronkelijke stukken bij een verzameld
Volume 1 (Google eBoek)
Cornelis Johan Lange van Wijngaarden, Jacobus Nicolaas Scheltema
Gebroeders van Cleef,
1813

p.627
(In het jaar 1378) 2 vaten hoenborgs bier, ghedronken waren en der verteert was

p.670
In het jaar 1363 had jacob die cuper 47 ame wijns verlaten. Het bier kwam van Haarlem, Amersfoort, der Goude en Schoonhoven, ook dronk men veel Hamburger bier, het welk men ook ter Goude nabrouwde

[one drank much Hamburg beer, and this was also copied in Gouda]

(3)
Stedelijk verleden in veelvoud
Opstellen over de laatmiddeleeuwse stadsgeschiedenis in de Nederlanden
Jeroen Benders
2011

(4)
Het Bier-oproer te Leeuwarden, in het jaar 1487
in zijne oorzaken en gevolgen: eene voorlezing (Google eBoek)
Jacob Dirks
1867

p.9-10

Kuit - het bier-oproer 1487

[Koyt - the beer uprising 1487]

(5)
Tegenwoordige Staat der Vereenigde Nederlanden
Volume 18 (Google eBoek)
Isaak Tirion,
1790

p.460
[even today in the summertime there is a very thin and also very tasty white beer being brewed under this designation]

(6a)
Volmaakte Geography:
Handelende van Bohemen, Oostenryk, Beyeren, Frankenland, Zwaben, Den Opper-Rhyn
(Google eBoek)
Johann Hübner
Haak,
1733

p.485
de Marck in Westphalen
Het Bier, Kuit genaamt, word wyd en zyd vervoert.

[The Marck in Westphalia
The beer called Kuit is transported far and wide.]

(6b)
Emergency money 1921
Motiv: Hammer Keut (Familienarchiv Schulte)
Urheber: Andreas Schulte 2007
1921