>
> This was in a Japanned tin that was sealed with lacquer, so that might
> have had something to do with it.
>

Undoubtedly so - for long keeping of tea the keys to success a

1. A well made tea - it has to be good quality at the start to end up
good quality after storing!
2. Correctly dried tea - to between 2 and 3% moisture content - must
incorporate a high temperature stage as all residual enzymes must be
"killed"
3. Absence of light - even well dried tea is still photochemically
active and will produce taints when illuminated.
4. An air tight container (tin or poly foil laminate - the container
must not leak (check - most storage tins made for tea are not airtight
at the seams; laminates can be pinholed and while they may not let
water through will allow air (inevitably damp) through)
5. Densely packed tea with minimal headspace (minimal amount of free
air - even tea without enzymes can continue chemical oxidation - leave
some green tea liquor overnight to see the color change). There's no
need for nitrogen or vac packing however, tea will soon scavenge a
small amount of oxygen in a minimal headspace.
6. Hermetically sealed (that means a complete and absolute barrier to
air exchange - if you wouldn't risk storing the pack under water then
you haven't got an hermetic seal)
7. Store cool in an even temperature (temperature change can induce
free water inside the container if the temperature drops - inside the
container tea equilibrates with the air and at 3% tea moisture the air
will have a dew point, albeit low, below which free water condenses).

I have not tried this on a 35 year test basis but recently was looking
for some old "tired" tea for a manufacturing faults class I was
teaching. Seeking this in my oldest tea samples I opened up a pouch
of black tea I had made in Pakistan in 1992. This had been processed
and dried under precise conditions in our miniature tea factory and
packed the same day in a heat sealed polyfoil pouch. Far from being
tired from long storage and despite being 15 years old it proved to be
as fresh, colory and flavorful as the day it was made.

Maybe we should set up Tea Banks - storing examples of our best teas
for the benefit of future generations of tea freaks in the same way
that seed banks are kept against loss of genetic material?

Nigel at Teacraft