To ensure a successful brew the brewing vessel should be consecrated
(kier vixling), some wort should be carried to the hill where the spirits
dwell. They also muttered magic words over the fermenting tub when
adding the yeast, this was to make the ale good. It was customary to
carry fire over the vessels to stop the evil forces from harming the ale.

Crosses were always carved into the bottom of the vessels. Red hot iron
rods and crosses were used to protect the ale. Before brewing a burning
branch should be swung in the doorway and over the vessels as
protection against witchcraft and the bad spirits.
Here  you see
Gustav
consecrating
our mashtun,
the use of fire
will drive the
bad spirirts
away.
In the old days, brewing in Norway was a sacred  act and the brewing
was left to the most respected person of a farms household. The brewer
always wore his best clothes when brewing. To make a strong brew the
brewer should be angry while brewing, the angrier the better and the
stronger the beer would become.
The little people were believed to do harm to those that brewed the ale.
If you had offended them in any way they might now take their revenge.
Here you see Gustav putting out a bowl of beer for the little people to
please them.
If the ale wouldn't ferment the little people might be holding the ale. The
best remedy was to take a horseshoe to the smithy and heat it until red
hot and then drop it into the fermenting tub. This would make the little
people loose their hold.