Hardness testers for
the food industry
How did the Bareiss company come
about, Mr. Wirth?
Oliver Wirth: The Bareiss company was
founded in 1954 by our grandfather, Heinrich
Bareiss. The aim was to build the best
and most accurate test equipment and to
continuously improve it. At that time, the
company began with analog measuring
devices, on which a pointer on a Shore
scale indicated up to 100 units. Over the
years, new ideas, patents and devices
have been developed from this in order to
simplify their use and to measure them
One milestone was,
for example, the
de ve lopment
of a hardness
Expert discussion with Katrin
Shen and Oliver Wirth,
managing partners of Bareiss
od to test finished parts with a wide variety
of geometries. We are so far unique in
this regard, since the hardness test traditionally
requires plane-parallel specimens
which, however, do not correspond to the
actual conditions of use.
What exactly is the physical measuring
Oliver Wirth: An indenter is attached
to a measuring rod, which in turn is supported
by a spring. The measuring rod
moves deeper or less deep into the material
with respect to the sample material.
If I were to press on a steel or glass plate,
the indenter has to disappear completely
in the pressure plate and the device has
to display the value 100.
The measurement and application
areas thus range from Shore 000 for
foams to the most well-known process,
Shore A, for elastomers, to Shore D
and Barcol for very hard materials,
such as plastics.
Where does the Shore unit
Katrin Shen: Albert Ferdinand Shore was
an American metallurgist who developed
the Shore durometer. Shore invented the
square durometer in 1915 for measuring
the hardness of polymers and other elastomers.
Various companies have used this
process for device construction. However,
Bareiss has further developed this process.
Now we come to topics related to the
food industry, such as fruit and vegetables.
How do you handle the measurement
of products such as cherries that
do not have plane-parallel surfaces?
Oliver Wirth: In the case of surfaces
that are not plane-parallel, the surface of
the object is touched and from there the
defined measuring path is driven downwards.
A printing plate is therefore only
necessary to a limited extent. This also enables
us to measure the hardness on spherical
To stay with the example of the cherry:
in the early stages a cherry will
presumably have similarly firm flesh
everywhere and thus a similar hardness
16 Hardness testers