202GF, A miracle glue?!

[Eddie Munster]

MW is correct.

Michael Williams wrote:

[J. Clarke]

[Agki Strodon]

I'm not getting this right, I don't think but if you are asking why water between the two sheets of glass doesn't just run out, here's why:

Three reasons are most important.

First, the intermolecular attraction between the positive hydrogen atoms in the polar water molecules and the negative oxygen atoms in the polar silicon dioxide molecules of the glass is greater than that between the water molecules themselves. This results in the "wetting" of the glass and the disappearance of the water's surface. The interaction keeps the water in place on the glass.

Second, there is air pressure at the edges of the glass pushing against the very thin water surface that occurs between the pieces of glass. Since the pressure is the same all around the resultant is a force pushing the water towards the center of the glass. It doesn't go there because of the considerations of "wetting" (as discussed above) pulling the water and forcing its dispersal over all the glass surfaces.

Third, there is also a thin surface of water at the edges of the water lamina forming a concave meniscus. This is the only place where surface tension exists in the system because it's the only water surface, there being no water surface inside the lamina. This is also a result of the first reason above.

Agkistrodon

[Agki Strodon]

I checked several maufacturers and other sites and found it about equally divided between smooth and roughed up. Who knows? I did not find any raw or reduced data but didn't look that hard.

Agkistrodon

[Agki Strodon]

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.

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

Absolute agreement.

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

[Agki Strodon]

If the silicone molecules inter-attract with the silicon dioxide molecules more strongly than they intra-attract amongst themselves, no. The plates would stick through wetting of the glass. They may be easy to separate and that is a way of finding the strength of the interactions.

As to whether anyone has done it, I dunno.

Agkistrodon

[Gerald Ross]

Does that mean that if you used something that wouldn't boil away, such as silicone, the two pieces of glass would not stick together in a vacuum? Has it been tried?

[Larry Jaques]

On Thu, 01 Jul 2004 18:29:00 GMT, "Agki Strodon" calmly ranted:

I'm sure he knew that it was the harmonic vibrations of the first 'snap' which multiplied in the pieces and facilitated further breaks.

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[Greg Millen]

Hmmm, interesting. My guess partially agrees with Lar. I'd say the harmonic from the initial break travels down the remaining stick until it reaches the second flex point. When the harmonic and the flex point meet, the spaghetti breaks.

Now, just how *do* brass screws permanently disappear in sawdust? Why is it so?

Groggy

[George]

They're attracted to pencils by the fifth force, the one that also causes socks to fly out of the dryer.

[Eddie Munster]

This phenomenon works with oils to. Or no fluids. and not using glass but any very flat surfaces. I would suspect if you reduced the air pressure in a chamber and measured the pll away forces of the two plates, nothing would change. Gosh it is even noticable at HD seperating sheets of plywood. What are Johansson blocks?

John

Agki Strod>>MW is correct.

[Fred the Red Shirt]

I think it depends on how rough and what sort of glue. With most any glue but epoxy the roughness must be small enough that you have a very thin layer accross the interface. If you roughen the surface to the point that the glue is filling gaps the result will be a weaker joint than if you just planed the surfaces smooth and glued them because the glue in the pockmarks will be weaker than the wood it replaced. I dunno where you cross the line between giving the glue tooth, and weakening the joint by requiring the glue to fill a gap.

I _think_ that a planed or scraped surface has the correct level of roughness for most glues, and does not have as many loose fibers or dust particles in the pores and does a surface roughened with sandpaper.

With epoxies, the glue in gaps is stronger than the wood and the strength can be maximized by eliminating the wood altogether, though the resulting furniture may leave something to be esthetically desired.

[Larry Jaques]

On Fri, 02 Jul 2004 09:09:07 GMT, "Greg Millen" calmly ranted:

That, sir, is due to the scavenger elf (with his brass magnet) who is hiding under all that sawdust and who absconds with them.

Nexxxxxt!

-- "Not always right, but never uncertain." --Heinlein -=-=-

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[Old Nick]

On Wed, 30 Jun 2004 19:23:03 -0400, Michael Williams vaguely proposed a theory ......and in reply I say!:

remove ns from my header address to reply via email

So the sheets would still stick together in a vacuum?

The surface tension of the ater is what stops the atmos pressure forcing the water out from between the glass, perhaps.

[Jay Pique]

parties. This is the wreck at its best.

Happy 4th of July all of you USAmericans!

JP

*************** Going "golfing" of all things today.....ugh.

[Howard Fairchild]

I must have missed the gist of the original post but here's some more useless info... If the glass plates are dead smooth, as in optical flats, and put together with nothing in between, they will be forever joined in a short while. No air space at all, there is a vacuum,, and the glass, an amorphous liquid, yep liquid, will grow together by molecular migration. This also applies to steel gage blocks as Johansen or Hoke blocks, but it takes a little longer for them to become a unit. Been there, done that.... This has no parallel to woodworking joint gaps, though... As for wood, cleanly cut, flat, preferably planed and not sanded, wood bonds better than rough wood any day.

Howie Metrologist