This text and the pictures are an excerpt from Ilkka Sysilä's
book Small-scale Brewing. The book is about brewing beer but it has a
marvellous chapter about Finnish Sahti. Small-scale Brewing is available from
Sahti Brewing Equipment
Traditional Sahti brewing gear consist of an open wooden mash tun,
a trough-like wooden lauter tun Kuurna and an upright three-legged
or four-legged wooden fermenter fitted with a spigot for dispensing
and serving the ready-fermented Sahti at its top condition straight
from the fermenter. Although the wooden fermenters have beer replaced by
40 liter aluminium milk cans, wooden mash tuns are still quite
common. Trough-like Kuurnas have not changed much and are still mostly
hand-crafted of wood probably because there is no industrially
produced easy-to-get either metal or plastic vessel capable of replacing
the traditional Kuurna.
Kuurna, the lauter tun
Kuurna, probably the most extraordinary lauter tun construction on
existence, is a wooden trough, typically 1,5-2,5 meters long and
around 0,4-0,5 meters wide and deep. The cross section of Kuurna's
inner surface is either curved (semicircular) or cut-conical
(with plane side walls inwardly slanting towards the plane
strip-like bottom). In the good old days Kuurnas were hollowed
out into a split log of a tree, usually aspen as it is fine-grained
and thus easy to work. The wooden Kuurnas of today are quite
often built of lumber or plywood. Prior to straining, the bottom
of the Kuurna is transversely lined with rung-like straight
pieces of wood, close enough to one another to make a grid atop of
which a false bottom is built traditionally of axially positioned
straws and fresh juniper twigs. One end of the Kuurna is fitted
with a bunghole at the level of the bottom for draining the wort.
Making of a traditional Kuurna
(Every picture is a link to the good quality version of
the picture. Bear in mind that those larger pictures are
quite big, more than 100 kb each.)
A log of aspen is first split. The log had dried over winter.
The inner part of the log is easily worked off using a chain saw...
...hewing further with an axe
...and finally with a chisel.
End bulkheads are made of lumber. Grooves are worked with
a chisel at the ends of the trough. The end bulkheads are embedded in
Steel band is used to tighten the end bulkhead fittings.
A bunghole is drilled through the other one of the two bulkheads.
The finished 2,5 meter long Kuurna ready for duty. Note
the transversely lines rungs on the bottom of the Kuurna and the
bunghole in the end bulkhead in the front.
Traditional Kuurna in action
Scooping the wort into the Kuurna. Note the
Draining the initial wort through the bunghole. Note the
traditional 40 liter milk can.