Hi Kayla,
The density of the blue food coloring (or rather, the molecular
weight, because when dissolved in water, the total density will be
close to that of water) probably won't stop the food coloring from
being absorbed by the celery stalk. Some things that might have an
effect -- the size of the blue dye particles might be so big that they
don't fit into the capillary tubes of the celery (probably not the case
for ordinary food coloring), and the miscibility of the food coloring
in the water may have an effect. Good food colorings dissolve easily in
water (unless you get an oil-based one to be used for coloring oils --
these probably won't be absorbed by celery). Normal food coloring dyes
are therefore are attracted to the electrically polar water molecules.
They should get dragged up the capillary tubes in the celery along with
the water.
I once bought some rather pretty blue flowers at a farmer's
market, and was initially surprised to find that the water in my flower
vase had turned bright blue after a couple of days. I think they
watered the flowers with water laced with blue food coloring to make
the flowers more blue than they naturally would be.
That having been said, you can check out
this site
on paper chromatography, or if the link goes away sometime, do a web
search for "paper chromatography". Different dyes will be attracted
more to paper or to water molecules, and this will affect the rate at
which they will migrate across a piece of paper through which water is
seeping by capillary action. If your blue food coloring is a mixture of
dyes, and celery has enough interesting properties, the separate dyes
in the food coloring may actually separate in the celery. I suspect
that paper will work better than celery for this, but it may happen.
Tom J.
(published on 10/22/2007)
