 The
high energy used in the rotary coater causes both increased friction
and raise of temperature (up to 35°C). For sensitive seeds or seed
lots this may give a risk for mechanical and/or physiological
damage. In one occasion a batch of lettuce seed showed 100% short
roots caused in the first minutes of the process.
Although
the potentially extreme short process time is a main success factor,
the reverse side of the medal is that an imbalance in powder and
liquid could disrupt the process in a very short time as well. In
the worst case this may lead to complete destruction of the coating
batch.
Drying
time is highly determined by the level of moisture imbibition. The
more and deeper the moisture has penetrated into the seed, the
longer time drying will take. Many species show a very fast water
uptake during the first 5-10 minutes and variation in coating time
may directly be reflected in drying time.
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