Hennotannic acid is a dye rather than a pigment
Posted by Catherine Cartwright Jones on March 02, 2000 at 20:26:54:
In Reply to: how to extract colour pigment from henna leaves for assured result? posted by atul mulay on March 02, 2000 at 15:53:11:
Hennotannic acid is a dye rather than a pigment .... (pigment is an
insoluble colored material that you suspend in medium like varnish to
make ink)
The most certain way to get henna to stain is to add something very
sour to powdered henna leaves. Henna releases dye in an acidic
environment. Mixing lemon or lime juice into henna powder and
leaving it a few hours is a very efficient way to get dye release. In
a standard 50x microscope field, lemon juice is 5 - 8 times more
effective than water at making dye release (so its available to bind
with collagen). There is a color release process ..... the dye stains
the skin most strongly in the 12 to 48 hours after adding acid ...
then diminishes over several more days until old henna paste barely
stains skin a sad tangerine color.
Hennotannic acid seems very reactive with oxygen .... so if you try
to just take hennotannic acid from the leaves (that brownish liquid
that appears at the surface of henna left out too long) it's not very
useful. Its reactivity diminishes on contact with air ... or that's
what I think I'm seeing, with the color sequence over several days.
If you want to see a gif of the dye molecule of henna .... email me.
Maybe you can make better sense of why exposure to air spoils the
dyeing power of henna than I can.
- Re: Hennotannic acid is a dye rather than a pigment atul 10:45:05 3/09/00
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