Interesting observation.

Main effect I would suggest is density of the leaf (tissue density,
not bulk density) and speed of saturation of the tissue.

Leaf density is mainly affected by rolling time (can be from 30 mins
to 200 mins), pressure (from light to heavy), and rolling table design
(a myriad of variations). When withered green leaf is rolled the
individual leaves are twisted (and small parts broken off), this
twisting increases the density of the large pieces of rolled leaf.
This will give a large "heavy leaf" that will tend to sink and as it
absorbs water it will expand and swirl. Poorly twisted "light leaf"
tends to float.

But the rate at which water is absorbed into the leaf is affected by
the degree of wither - which influence the amount of cell sap squeezed
out (for a given rolling pressure), and the viscosity of that sap.

It is noticeable that at different times of the year and with
different wither conditions the rolled leaf is sometimes very sticky
to the touch, and less so at others.

The viscosity of exuded sap depends on the a) amount of water removed
in wither (a hard wither gives stickier juice), and b) the sap
condition when plucked (climatic effects). When rolling ceases the
exuded sticky juices are absorbed back into the twisted leaf (during
oxidation). Subsequent drying at high temperature fixes the "glue".

A hard glued well twisted leaf will absorb water less quickly, thus
will sit on the bottom of the vessel for a while - slow swirler.
A hard glued poorly twisted leaf will float until it absorbs water
slowly - slow sinker.
A poorly glued heavy leaf will swirl quickly - fast swirler
While a poorly glued light leaf will float momentarily as it absorbs -
a fast sinker

All these effects will be influenced by water temperature. Water
becomes less viscous as it is heated, thus leaves that might float in
cold water would sink in hot. The dried oxidised sap (glue) disolves
more quickly in boiling water than in warm, than in cold. Thus the
"Agony" is perhaps best performed in the hottest of water.

Nigel at Teacraft
www.teacraft.com
www.nbtea.co.uk


(Space Cowboy) wrote in message . com...
My commercial grades from OP on down swim like a fish before saying hi
to their maker. I noticed about half of my estate grades sink like a
rock while the others will matte and slowly sink to their final
resting place. For the ones that don't indicate any agony I wonder if
that is normal? I'm thinking withering and oxidation may effect the
dance otherwise any leaf will float. I recently switched back to a
see through pot and wanted to make sure the phenomenon wasn't
isolated. I even exposed some of my best swimmers to light and air
for staleness and it didn't make any difference. Any ideas?

Thanks,
Jim