Harnessing the power of 'super
cooled liquids', Instant Heat Packs contain sodium acetate and
water. Sodium acetate is very good at super cooling - it ‘freezes’
at 130º F (54º C), but will exist as a liquid at a much lower
temperature and is extremely stable. Clicking the small disc inside
forces a few molecules to change to the solid state, and the rest
of the liquid quickly follows until the temperature of the
solidifying liquid reaches 130º F.
Using the Heat Packs couldn’t be
simpler: the product has 2 forms, liquid (soft, jelly-like &
translucent) and crystallised (firm & opaque). The liquid state
is the ‘Ready For Use’ state, and can be activated anytime,
anywhere. Click or flex the little metal disc inside the pouch, and
you see crystals forming and feel heat being generated immediately.
While the liquid is going through the crystallisation process, it's
helpful to massage or knead the pack with your fingers (which can
actually be a therapy in itself). The liquid becomes firm to the
touch and opaque rather than translucent. The Heat Pack is now at
54º C, so, although it's safe for everyone, including children, the
elderly and the infirm, care must be taken, as with any hot object.
The pack remains warm for some
time, although this will vary according to the ambient temperature
etc. When the pack has cooled down, it can be ‘reset’, ready to be
used again, by being placed in a pan of boiling water, and boiled
for 5 -15 minutes (depending on the size of heat pack) until all
the crystals have gone. Leave to cool and it's ready for use again.
It can be chilled in the fridge, but must not be frozen.