"Michael Williams" wrote in message
...
Hmmm. I don't think you have this quite right. According to your
description, why wouldn't the water just be forced out of the gap?

The sheets are held together because of the surface tension of the laminar
fluid layer.

There is NO surface tension inside the fluid layer. There cannot be because
there is no surface inside the water layer. The water wets the glass and
the interactions occur between water and glass molecules. Surface tension
occurs only at the edges of the lamina because surface tension is defined as
the intermolecular attraction between the molecules of the fluid at the
boundary of the fluid. Surface tension works against wetting and the
superiority of the SiO2 - H2O interaction over the H2O - H20 interaction
accounts for the wetting of the glass. If you smear paraffin on the glass
and then put water on it, the water will bead up and retain surfaces (and
surface tension) because the water-water attractive forces are greater than
the water-paraffin attractive forces.

Pulling the sheets apart would seriously increase the free
surface area of the fluid which surface tension seeks to minimize.

To the force of air pressure holding the plates together, we can add the
resultant force of all them damned SiO2 - H20 attractions. I think, though,
that it's rather small compared to the air pressure. We could set up an
apparaturs to measure it.

I think
it is pretty clear that this has nothing to do with the bonding in glue
joints, since, after all, the glue in short order ceases to be a fluid.

Absolute agreement.

Cohesion (- surface tension) is important, but adhesion is the key.
Roughing the surfaces, as most glue manufacturers recommend, exploits this
aspect. However, glue films should be thin, just not too thin. Have you
ever been impressed by the strength of a cured gob of glue?

However, it is far to easy to over-generalize when speaking of glue.

-mw

Quite so! Now for the biggest question in physics - one that Feynman and
the physics faculty at Cal Tech could not answer- why does a stick of
spaghetti almost always break into three or more pieces when you bend it by
the ends?

Agkistrodon