Lisa, the immersion Tin process is inherently unstable.

The Tin is reasonably easily oxidized from Stannous state, where it is more
or less soluble, to the Stannic state, where it is totally insoluble, and
will not plate.  The higher the temperature, and the longer it sits there,
the more this happens.

Further, the bath contains Thiourea, which is also somewhat unstable, and the
higher the temperature, the more quickly it decomposes...

So, yes, there is reason for you to experience problems on high temperature
use.

All of these problems go away if you use the chemical fast enough for it to
need replenishing frequently, which is why I made the comment.

Rudy Sedlak
RD Chemical Company

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