The Garrett -Wade catalog has a PVA glue that it claims:
1) It fills gaps with strength
2) Squeeze out does not penetrate the wood and easily chips off when dried,
no need for scrapping.

If it actually does this I will certainly use it, but it seems like bull
when an obsure brand is radically superior to the successful brands.

Has anyone used it. (Hey, occassionally my joints have gaps...)

Well if it is like the Lee Valley 202GF, then yes. Fills gaps with
strength? I've never tested it, but it does indeed fill gaps. I like the
brown colour too. I have to shake it up real well before use as it the
solids settle out.

John

toller wrote:
The Garrett -Wade catalog has a PVA glue that it claims:
1) It fills gaps with strength
2) Squeeze out does not penetrate the wood and easily chips off when dried,
no need for scrapping.

If it actually does this I will certainly use it, but it seems like bull
when an obsure brand is radically superior to the successful brands.

Has anyone used it. (Hey, occassionally my joints have gaps...)

toller wrote:

The Garrett -Wade catalog has a PVA glue that it claims:
1) It fills gaps with strength
2) Squeeze out does not penetrate the wood and easily chips off when dried,
no need for scrapping.

I wonder how it holds a joint together if it "does not penetrate the wood and
easily chips off when dried"?

--
Jack Novak
Buffalo, NY - USA
(Remove "SPAM" from email address to reply)

Yeah, I was thinking, what good is a glue that will chip off wood when
dried?

"Nova" wrote in message
...
toller wrote:

The Garrett -Wade catalog has a PVA glue that it claims:
1) It fills gaps with strength
2) Squeeze out does not penetrate the wood and easily chips off when
dried,
no need for scrapping.

I wonder how it holds a joint together if it "does not penetrate the wood
and
easily chips off when dried"?

--
Jack Novak
Buffalo, NY - USA
(Remove "SPAM" from email address to reply)

"toller" wrote in message ...
The Garrett -Wade catalog has a PVA glue that it claims:
1) It fills gaps with strength
2) Squeeze out does not penetrate the wood and easily chips off when dried,
no need for scrapping.

If it actually does this I will certainly use it, but it seems like bull
when an obsure brand is radically superior to the successful brands.

Has anyone used it. (Hey, occassionally my joints have gaps...)

I've used the 2002GF glue from Lee Valley and love it. Never tried its
gap filling ability, but its extended working time and thickness make
it a pleasure to use.

"Nova" wrote in message
...
toller wrote:

The Garrett -Wade catalog has a PVA glue that it claims:
1) It fills gaps with strength
2) Squeeze out does not penetrate the wood and easily chips off when
dried,
no need for scrapping.

I wonder how it holds a joint together if it "does not penetrate the wood
and
easily chips off when dried"?


How about glues that hold metal pieces together. They don't penetrate the
metal. The problem is the strength of the glue bond to each piece and the
internal strength of the glue layer itself. A roughed up surface holds
better than a smooth one because there's more glue in the between pieces
volume, ain't it?

If it chips off easily, it doesn't seem to mean that the bond itself will be
weak. The stresses would be different, wouldn't they?

Agkistrodon

"Scott Wilson" wrote in message

I've used the 2002GF glue from Lee Valley and love it. Never tried its
gap filling ability, but its extended working time and thickness make
it a pleasure to use.

Same here. I prefer it to the big name brands.

Don't know if the 202GF from Garrett Wade is the same as the 2002GF from Lee
Valley though.
Ed

"toller" wrote in message
...
The Garrett -Wade catalog has a PVA glue that it claims:
1) It fills gaps with strength
2) Squeeze out does not penetrate the wood and easily chips off when
dried,
no need for scrapping.

If it actually does this I will certainly use it, but it seems like bull
when an obsure brand is radically superior to the successful brands.

Has anyone used it. (Hey, occassionally my joints have gaps...)



I've used Garrett Wade 202GF for at least ten years. It's good. Joints are
strong, it does fill gaps, and excess does chip off.

--
Conehead

Anybody remember the name of a wood airframe German fighter airplane
developed around 1943-44 that had two engines? As I recall from the History
Channel, it was supposed to be a terror in the air but the Germans couldn't
put it into production because the vibration shook the wood joints apart
unless they used a special glue. The factory that made the glue was bombed,
the formula burned up in the fire, and the glue chemists apparently killed
in the attack.

Agkistrodon

"Agki Strodon" wrote in message
nk.net...


How about glues that hold metal pieces together. They don't penetrate the
metal. The problem is the strength of the glue bond to each piece and the
internal strength of the glue layer itself. A roughed up surface holds
better than a smooth one because there's more glue in the between pieces
volume, ain't it?

A roughed up surface does not necessarily mean a better bond. Have you ever
laid a pane of glass on top of another with water between the two? Almost
impossoble to pull apart because of the surface tension.

"conehead" wrote in message
...
"toller" wrote in message
...
The Garrett -Wade catalog has a PVA glue that it claims:
1) It fills gaps with strength
2) Squeeze out does not penetrate the wood and easily chips off when
dried,
no need for scrapping.

If it actually does this I will certainly use it, but it seems like bull
when an obsure brand is radically superior to the successful brands.

Has anyone used it. (Hey, occassionally my joints have gaps...)



I've used Garrett Wade 202GF for at least ten years. It's good. Joints
are
strong, it does fill gaps, and excess does chip off.

Still hard to believe, but worth $7 to find out. Thanks.

"Leon" wrote in message
m...

"Agki Strodon" wrote in message
nk.net...


How about glues that hold metal pieces together. They don't penetrate
the
metal. The problem is the strength of the glue bond to each piece and
the
internal strength of the glue layer itself. A roughed up surface holds
better than a smooth one because there's more glue in the between pieces
volume, ain't it?

A roughed up surface does not necessarily mean a better bond. Have you
ever
laid a pane of glass on top of another with water between the two? Almost
impossoble to pull apart because of the surface tension.



But that's a different physical phenomenon.

Agkistrodon

"Agki Strodon" writes:

Anybody remember the name of a wood airframe German fighter airplane
developed around 1943-44 that had two engines? As I recall from the
History
Channel, it was supposed to be a terror in the air but the Germans
couldn't
put it into production because the vibration shook the wood joints apart
unless they used a special glue. The factory that made the glue was
bombed,
the formula burned up in the fire, and the glue chemists apparently killed
in the attack.


Can't help with the German glue, but the Brits used Aerolite 306.

BTW, I still have some.


--
Lew

S/A: Challenge, The Bullet Proof Boat, (Under Construction in the Southland)
Visit: http://home.earthlink.net/~lewhodgett for Pictures

Agki Strodon wrote:

Anybody remember the name of a wood airframe German fighter airplane
developed around 1943-44 that had two engines? As I recall from the
History Channel, it was supposed to be a terror in the air but the Germans
couldn't put it into production because the vibration shook the wood
joints apart unless they used a special glue. The factory that made the
glue was bombed, the formula burned up in the fire, and the glue chemists
apparently killed in the attack.

Sounds like the Messerschmitt 328 twin pulsejet.

Wasn't the only wooden aircraft in WWII, though. The British Mosquito was
for a while during WWII the fastest airplane in the world, and I believe
the only high performance wooden aircraft of WWII to go into volume
production. The German Go.220 twin turbojet would have been a terror if it
had been developed in time, but the factory was captured just as they were
getting ready to start production. Then there were the He 162 variants.




Agkistrodon

--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)

Agki Strodon wrote:


"Nova" wrote in message
...
toller wrote:

The Garrett -Wade catalog has a PVA glue that it claims:
1) It fills gaps with strength
2) Squeeze out does not penetrate the wood and easily chips off when
dried,
no need for scrapping.

I wonder how it holds a joint together if it "does not penetrate the wood
and
easily chips off when dried"?


How about glues that hold metal pieces together. They don't penetrate the
metal. The problem is the strength of the glue bond to each piece and the
internal strength of the glue layer itself. A roughed up surface holds
better than a smooth one because there's more glue in the between pieces
volume, ain't it?

As a general rule, a _clean_ surface holds better. Roughness doesn't
improve bond strength with most adhesives and substrates and in many cases
it weakens the bond.

If it chips off easily, it doesn't seem to mean that the bond itself will
be
weak. The stresses would be different, wouldn't they?

Agkistrodon

--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)

Lew Hodgett wrote:


"Agki Strodon" writes:

Anybody remember the name of a wood airframe German fighter airplane
developed around 1943-44 that had two engines? As I recall from the
History
Channel, it was supposed to be a terror in the air but the Germans
couldn't
put it into production because the vibration shook the wood joints apart
unless they used a special glue. The factory that made the glue was
bombed,
the formula burned up in the fire, and the glue chemists apparently
killed in the attack.


Can't help with the German glue, but the Brits used Aerolite 306.

BTW, I still have some.

It's still in production. Good rundown on it at
http://www.seqair.com/skunkworks/Glues/Aerolite/Aerolite.html.

--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)

In article et, "Agki Strodon" wrote:
How about glues that hold metal pieces together. They don't penetrate the
metal. The problem is the strength of the glue bond to each piece and the
internal strength of the glue layer itself. A roughed up surface holds
better than a smooth one because there's more glue in the between pieces
volume, ain't it?

No, a (slightly) roughened surface holds better than a smooth one because
there is more surface area for the glue to bond to.

--
Regards,
Doug Miller (alphageek-at-milmac-dot-com)

Get a copy of my NEW AND IMPROVED TrollFilter for NewsProxy/Nfilter
by sending email to autoresponder at filterinfo-at-milmac-dot-com
You must use your REAL email address to get a response.

"Agki Strodon" wrote in message news:aKqEc.2199

But that's a different physical phenomenon.

Is it? The water like glue displaces the air that is between the 2
surfaces. If there is a spot in a glued up joint that has an air space, the
joint is week at that point




Agkistrodon

"Agki Strodon" wrote in message link.net...
Anybody remember the name of a wood airframe German fighter airplane
developed around 1943-44 that had two engines?

I can find it tonight. AFAIR, it was colloquially known as "mosquito"
(or the German equivalent) because it was a deliberate attempt to copy
the De Havilland.

the Germans couldn't
put it into production because the vibration shook the wood joints apart
unless they used a special glue.

Tegofilm. They did make them without it, using an alternative glue,
but they broke up in flight.

Towards the end, there were several German aircraft with wooden
fuselages, if not wooden wings too. Natter and Salamander are some of
the more famous of the "desperation weapons".

Well when the glue dries, then it is a different phenomenon.

John

Leon wrote:
"Agki Strodon" wrote in message news:aKqEc.2199


But that's a different physical phenomenon.


Is it? The water like glue displaces the air that is between the 2
surfaces. If there is a spot in a glued up joint that has an air space, the
joint is week at that point




Agkistrodon

The 202gf seems to be cheaper than titebond III and Gorilla glue. If it
is also waterproof why bother with the others?

Len
----------

conehead wrote:
"toller" wrote in message
...

The Garrett -Wade catalog has a PVA glue that it claims:
1) It fills gaps with strength
2) Squeeze out does not penetrate the wood and easily chips off when

dried,

no need for scrapping.

If it actually does this I will certainly use it, but it seems like bull
when an obsure brand is radically superior to the successful brands.

Has anyone used it. (Hey, occassionally my joints have gaps...)




I've used Garrett Wade 202GF for at least ten years. It's good. Joints are
strong, it does fill gaps, and excess does chip off.

--
Conehead

"Leon" wrote in message
news

"Agki Strodon" wrote in message
news:aKqEc.2199

But that's a different physical phenomenon.

Is it? The water like glue displaces the air that is between the 2
surfaces. If there is a spot in a glued up joint that has an air space,
the
joint is week at that point


I don't want to be seen as a pedantic jerk by you chaps even though my
students often called me one but:

Glass sheets are held together by water between them because the water has
driven out the air and occupies the space between the two sheets. The
sheets themselves are then forced together (and against the water lamina) by
the air pressure that pushes them together at about 14 lb/sq in. The only
mediating pressure is the very slight air pressure on the thin lamina of
water between the sheets of glass that forces the water to push outward
against the sheets by pushing inward on the water. Surface tension has not
much to do with it unless there is an interactive attractive force in the
glass (or whatever) that pulls the water molecules toward the sheet but this
would be very slight in almost all cases of materials. Air pressure is the
force both holding the sheets together and, to an extremely small degree,
pushing them apart by pushing on the water lamina. If the glass sheets are
uniformly flat and measure, say 10"x10", each sheet is 100 sq in. The air
pressure produces 14 lb/sq in on each sheet so the total is [14 lb/sq in x
100 sq in/sheet x 2 sheets] - [the pressure on the water from the sides], or
2800 lb. (I ignored the very very slight pressure on the water lamina
because it close to zero). 2800 pounds is the amount of force needed to
separate the sheets if there's no other factor. We don't need that much
because when we slide the sheets over each other we reduce the amount of air
pressure push against them at the places where they are together. Finally,
by sliding the sheets enough, the holding pressure is reduced to an easy
force to apply.

Glues work differently and don't depend on air pressure to hold things
together. There are essentially two aspects, the adhesion of the glue to
the surfaces and the internal bonding strength between the molecules that
make up the glue itself. The solvent for the glue (water, alcohol,
whatever) is just a carrier. The glue dries by losing its carrier and (in
some cases) the chemical nature of the glue itself changes when that
happens. When it dries, it bonds to the things being glued and internally
inside the dab of glue between them. In the old days, both these bonds were
relatively weak and either the glue's internal bonds broke or the bond with
the material broke. Some glues produce bonds to materials that are stronger
than the material itself is internally AND the internal glue intermolecular
strength is also stronger.

Spaces in glued up joints produce weakness because theres no glue in the
spaces to form a bond.

Agkistrodon

"Edwin Pawlowski" wrote in message
. ..

"Scott Wilson" wrote in message

I've used the 2002GF glue from Lee Valley and love it. Never tried its
gap filling ability, but its extended working time and thickness make
it a pleasure to use.

Same here. I prefer it to the big name brands.

Don't know if the 202GF from Garrett Wade is the same as the 2002GF from
Lee
Valley though.
Ed


They may be the same formula because they all kinds look alike and are in
the same price range. The Lee Valley 2002GF is about USD 11.00/liter and
the GW 202GF is about USD 12.00/quart.

I've never seen it sold here in Durham or Raleigh, NC, CSA but I'm going to
order some of each. Maybe some experiments and a report?

Agkistrodon

"Agki Strodon" wrote in message
hlink.net...

I don't want to be seen as a pedantic jerk by you chaps even though my
students often called me one but:

Glass sheets are held together by water between them because the water has
driven out the air and occupies the space between the two sheets. The
sheets themselves are then forced together (and against the water lamina)
by
the air pressure that pushes them together at about 14 lb/sq in. The only
mediating pressure is the very slight air pressure on the thin lamina of
water between the sheets of glass that forces the water to push outward
against the sheets by pushing inward on the water. Surface tension has not
much to do with it unless there is an interactive attractive force in the
glass (or whatever) that pulls the water molecules toward the sheet but
this
would be very slight in almost all cases of materials. Air pressure is
the
force both holding the sheets together and, to an extremely small degree,
pushing them apart by pushing on the water lamina. If the glass sheets
are
uniformly flat and measure, say 10"x10", each sheet is 100 sq in. The air
pressure produces 14 lb/sq in on each sheet so the total is [14 lb/sq in x
100 sq in/sheet x 2 sheets] - [the pressure on the water from the sides],
or
2800 lb. (I ignored the very very slight pressure on the water lamina
because it close to zero). 2800 pounds is the amount of force needed to
separate the sheets if there's no other factor. We don't need that much
because when we slide the sheets over each other we reduce the amount of
air
pressure push against them at the places where they are together.
Finally,
by sliding the sheets enough, the holding pressure is reduced to an easy
force to apply.

Glues work differently and don't depend on air pressure to hold things
together. There are essentially two aspects, the adhesion of the glue to
the surfaces and the internal bonding strength between the molecules that
make up the glue itself. The solvent for the glue (water, alcohol,
whatever) is just a carrier. The glue dries by losing its carrier and (in
some cases) the chemical nature of the glue itself changes when that
happens. When it dries, it bonds to the things being glued and internally
inside the dab of glue between them. In the old days, both these bonds
were
relatively weak and either the glue's internal bonds broke or the bond
with
the material broke. Some glues produce bonds to materials that are
stronger
than the material itself is internally AND the internal glue
intermolecular
strength is also stronger.

Spaces in glued up joints produce weakness because theres no glue in the
spaces to form a bond.

Agkistrodon




Yea, that's just what I was gonna say. :-)
--
********
Bill Pounds
http://www.billpounds.com

Yea, that's just what I was gonna say. :-)
--
********

What? The part about being a pedantic jerk??? Hell, I know it! And I
don't give a flip, either.

Agkistrodon

Towards the end, there were several German aircraft with wooden
fuselages, if not wooden wings too. Natter and Salamander are some of
the more famous of the "desperation weapons".

Yeah, the history if some of the designs they had for future planes would
have made Wernher von Braun proud. One Messerschmitt design was captured by
the Americans and became the F-86 Saberjet used a lot in Korea. I'm not
sure about the designer but there was also a design (Focke-Wulf?) captured
by the Russians that became the MiG -8(?) that fought the F-86s. So, the
Luftwaffe kept on flying!!

Agkistrodon

"Agki Strodon" wrote in message
hlink.net...
..

Spaces in glued up joints produce weakness because theres no glue in the
spaces to form a bond.



Now you are beginning to show signs that you understand the point that I was
trying to make. You stated,

"Agki Strodon" wrote in message
news:4TCEc.20861$bs4.13057

Spaces in glued up joints produce weakness because theres no glue in the
spaces to form a bond.

Now you are showing signs that you might understand the point that I was
trying to make.

You said,

"A roughed up surface holds better than a smooth one because there's more
glue in the between pieces volume, ain't it?"

Roughed up surfaces often cause spaces in the glued up joint. A smooth
surface is Ideal for glue.

"Leon" wrote in message
m...

"Agki Strodon" wrote in message
news:4TCEc.20861$bs4.13057

Spaces in glued up joints produce weakness because theres no glue in the
spaces to form a bond.

Now you are showing signs that you might understand the point that I was
trying to make.

You said,

"A roughed up surface holds better than a smooth one because there's more
glue in the between pieces volume, ain't it?"

Roughed up surfaces often cause spaces in the glued up joint. A smooth
surface is Ideal for glue.



That is really debatable, mein Herr. It depends. If the glue can get into
the roughed up spaces, it will be stronger because there will be more glue
in the joint as a result of the increased surface area caused by the
roughening up. The gap causes a weakened area of the joint relative to the
rest of it because there's no glue there. This calls for scientific
investigation!! Roughed up vs. smooth glued surfaces. Aha, something I
know about.

If I do some sexperiments, would anyone want the results?
How would you design the set of experiments? I'll do them this weekend.

Agkistrodon

"Agki Strodon" wrote in message
link.net...

If I do some sexperiments, would anyone want the results?
How would you design the set of experiments? I'll do them this weekend.

I believe the glue companies already have this data. IIRC their
recommendation is a smooth surface. Hence there are rip blades made for
glue line ripping that produce smooth surfaces. Jointers straighten a
board and produce smooth surfaces for gluing.
Thick glue in a joint is not desirable. It is usually an indicator of a
poor joint that does not fit well. Roughing up a surface has little value
for gluing as the surface produced from roughing up leaves loose and weak
fibers of wood.

"Agki Strodon" writes:

If I do some sexperiments, would anyone want the results?
How would you design the set of experiments? I'll do them this weekend.



First step - glue together two end-joint pieces. The ends are always
rougher than the sides. So the glue should hold better according to
the theory you are testing.

Some of you may have already done this... :-)


--
Sending unsolicited commercial e-mail to this account incurs a fee of
$500 per message, and acknowledges the legality of this contract.

On Wed, 30 Jun 2004 18:16:38 GMT, "Agki Strodon"
wrote:


The German "mosquito clone" aircraft was the Ta-154, designed by Kurt
Tank and so it's also referred to as a Focke Wulf. As I thought, it
was also named "Moskito"

I don't know what Tego-Film replacement was, but my sources describe
it as a cold glue that had problems with residual acid. Maybe it was
an early PVA ?

Yeah, the history if some of the designs they had for future planes would
have made Wernher von Braun proud.

I doubt it - he just did rockets
("That's not my department", says Wernher von Braun)

One Messerschmitt design was captured by
the Americans and became the F-86 Saberjet used a lot in Korea.

No, this was the P.1101. It was captured almost complete in
Oberammergau, generally ignored for years and NASA later flew it as
the Bell (sic) X-5. The original version had a variable sweep wing
that was ground adjustable, but Bell developed this to allow in-flight
sweep changes. Last person to fly it was some guy called Neil
Armstrong.

The F-86 almost entirely ignored the German swept wing research. What
the Americans learned about sweep, they mainly picked up from the
British.

The first supersonic jet to fly was the DH108 Swallow, a swept wing
tailless development of the 1943 Spider Crab - both with short and
tubby wooden fuselage sections, built by the Mosquito laminated wood
sheet production technique. However the Swallow was a bit of a widow
maker and all three prototypes killed their pilots. Not before
however, almost certainly becoming the first supersonic jet, albeit
unrecorded and in a near-fatal dive.

Germany's tailless Gothas and Hortens would probably have suffered
similar problems, had they ever been flown under real power.

The first supersonic aircraft was of course the Miles M.52. Cancelled
by a short-sighted British government in 1946, the first real test
wasn't until a model flight in 1948 - when it promptly achieved M1.38
in level flight, with no fuss at all.

The Russians weren't so daft. They copied everything Messerschmitt did
with swept wings and produced the Mig-15 and Mig-17 on the basis of
them. However, given what the British did by giving them Nene engines
to power them, no doubt we'd have given them wing designs too, if
they'd asked.


The Me328 (twin pulse jets) was a dismal failure. The wooden fuselage
was destroyed by the intense acoustic noise from the pulse jets, so
they were moved off the fuselage and under the wings. Here they became
uncontrollable, as pulsejets aren't easily throttled to balance their
thrust. Unbalanced thrusts such a long way from the centre line gave
it a tendency to yaw wildly - and the fuselage still fell apart.

--
If we fail, then let us fail heroically
(or even better, stoichiometrically)

Agki Strodon wrote:


Towards the end, there were several German aircraft with wooden
fuselages, if not wooden wings too. Natter and Salamander are some of
the more famous of the "desperation weapons".

Yeah, the history if some of the designs they had for future planes would
have made Wernher von Braun proud. One Messerschmitt design was captured
by
the Americans and became the F-86 Saberjet used a lot in Korea.

Not quite. A lot of German data on swept wings was used in the design of
the F-86, but it was not a German design or a copy of one. The US did
capture the P.1101 prototype, of which the Bell X-5 was a partial clone.
Other than being a swept-wing jet it bore little resemblance to the F-86.

I'm not
sure about the designer but there was also a design (Focke-Wulf?) captured
by the Russians that became the MiG -8(?) that fought the F-86s.

TA-183. The Mig-15 looks a little bit like it but a long way from being a
clone.

So, the
Luftwaffe kept on flying!!

Agkistrodon

--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)

"Agki Strodon" said:
A roughed up surface holds better than a smooth one because there's
more glue in the between pieces volume, ain't it?

"Agki Strodon" said:
Spaces in glued up joints produce weakness because theres no glue in
the spaces to form a bond.

Forget the physics... wood fibers are held together by lignin and xylan,
woodworking glues mimic natural glues by bonding the wood fibers together.
That's why it isn't necessary for the glue to soak in and why a smoother
(planed) wood surface holds better than a rough (sawed/sanded) surface.
--
Mac Cool

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


On 6/30/04 1:37 PM, in article
.net, "Agki Strodon"
wrote:


"Leon" wrote in message
news

"Agki Strodon" wrote in message
news:aKqEc.2199

But that's a different physical phenomenon.

Is it? The water like glue displaces the air that is between the 2
surfaces. If there is a spot in a glued up joint that has an air space,
the
joint is week at that point


I don't want to be seen as a pedantic jerk by you chaps even though my
students often called me one but:

Glass sheets are held together by water between them because the water has
driven out the air and occupies the space between the two sheets. The
sheets themselves are then forced together (and against the water lamina) by
the air pressure that pushes them together at about 14 lb/sq in. The only
mediating pressure is the very slight air pressure on the thin lamina of
water between the sheets of glass that forces the water to push outward
against the sheets by pushing inward on the water. Surface tension has not
much to do with it unless there is an interactive attractive force in the
glass (or whatever) that pulls the water molecules toward the sheet but this
would be very slight in almost all cases of materials. Air pressure is the
force both holding the sheets together and, to an extremely small degree,
pushing them apart by pushing on the water lamina. If the glass sheets are
uniformly flat and measure, say 10"x10", each sheet is 100 sq in. The air
pressure produces 14 lb/sq in on each sheet so the total is [14 lb/sq in x
100 sq in/sheet x 2 sheets] - [the pressure on the water from the sides], or
2800 lb. (I ignored the very very slight pressure on the water lamina
because it close to zero). 2800 pounds is the amount of force needed to
separate the sheets if there's no other factor. We don't need that much
because when we slide the sheets over each other we reduce the amount of air
pressure push against them at the places where they are together. Finally,
by sliding the sheets enough, the holding pressure is reduced to an easy
force to apply.

Glues work differently and don't depend on air pressure to hold things
together. There are essentially two aspects, the adhesion of the glue to
the surfaces and the internal bonding strength between the molecules that
make up the glue itself. The solvent for the glue (water, alcohol,
whatever) is just a carrier. The glue dries by losing its carrier and (in
some cases) the chemical nature of the glue itself changes when that
happens. When it dries, it bonds to the things being glued and internally
inside the dab of glue between them. In the old days, both these bonds were
relatively weak and either the glue's internal bonds broke or the bond with
the material broke. Some glues produce bonds to materials that are stronger
than the material itself is internally AND the internal glue intermolecular
strength is also stronger.

Spaces in glued up joints produce weakness because theres no glue in the
spaces to form a bond.

Agkistrodon

On Wed, 30 Jun 2004 19:23:03 -0400, Michael Williams
wrote:

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

In the course of learning to work wood, I suppose it would do me good
to learn about adhesives. Any recommended tomes on the subject? I
don't need "all" the science, but I would like to see coverage similar
to that presented in Flexner or Jewitt's finishing books.

kiitos
JP


-mw


On 6/30/04 1:37 PM, in article
k.net, "Agki Strodon"
wrote:


"Leon" wrote in message
news

"Agki Strodon" wrote in message
news:aKqEc.2199

But that's a different physical phenomenon.

Is it? The water like glue displaces the air that is between the 2
surfaces. If there is a spot in a glued up joint that has an air space,
the
joint is week at that point


I don't want to be seen as a pedantic jerk by you chaps even though my
students often called me one but:

Glass sheets are held together by water between them because the water has
driven out the air and occupies the space between the two sheets. The
sheets themselves are then forced together (and against the water lamina) by
the air pressure that pushes them together at about 14 lb/sq in. The only
mediating pressure is the very slight air pressure on the thin lamina of
water between the sheets of glass that forces the water to push outward
against the sheets by pushing inward on the water. Surface tension has not
much to do with it unless there is an interactive attractive force in the
glass (or whatever) that pulls the water molecules toward the sheet but this
would be very slight in almost all cases of materials. Air pressure is the
force both holding the sheets together and, to an extremely small degree,
pushing them apart by pushing on the water lamina. If the glass sheets are
uniformly flat and measure, say 10"x10", each sheet is 100 sq in. The air
pressure produces 14 lb/sq in on each sheet so the total is [14 lb/sq in x
100 sq in/sheet x 2 sheets] - [the pressure on the water from the sides], or
2800 lb. (I ignored the very very slight pressure on the water lamina
because it close to zero). 2800 pounds is the amount of force needed to
separate the sheets if there's no other factor. We don't need that much
because when we slide the sheets over each other we reduce the amount of air
pressure push against them at the places where they are together. Finally,
by sliding the sheets enough, the holding pressure is reduced to an easy
force to apply.

Glues work differently and don't depend on air pressure to hold things
together. There are essentially two aspects, the adhesion of the glue to
the surfaces and the internal bonding strength between the molecules that
make up the glue itself. The solvent for the glue (water, alcohol,
whatever) is just a carrier. The glue dries by losing its carrier and (in
some cases) the chemical nature of the glue itself changes when that
happens. When it dries, it bonds to the things being glued and internally
inside the dab of glue between them. In the old days, both these bonds were
relatively weak and either the glue's internal bonds broke or the bond with
the material broke. Some glues produce bonds to materials that are stronger
than the material itself is internally AND the internal glue intermolecular
strength is also stronger.

Spaces in glued up joints produce weakness because theres no glue in the
spaces to form a bond.

Agkistrodon

"Jay Pique" wrote ...
In the course of learning to work wood, I suppose it would do me good
to learn about adhesives. Any recommended tomes on the subject? I
don't need "all" the science, but I would like to see coverage similar
to that presented in Flexner or Jewitt's finishing books.

You don't really need a book if you read Chapter 9 of the Forest Products
Lab Handbook (link below). It outlines the properties of a properly
prepared surface and discusses, in detail, the fact that glue bonding is
almost entirely a mechanical process rather than a chemical one. It sounds
like several people in this thread may benefit from reading Chapter 9. You
can download it - FOR FREE (the best part)- right he
http://www.fpl.fs.fed.us/documnts/FP.../fplgtr113.htm

--

Cheers,
Howard

----------------------------------------------------------
Working wood in New Jersey -
Visit me in the woodshop - www.inthewoodshop.org

On Tue, 29 Jun 2004 16:38:05 -0400, Nova
wrote:

toller wrote:

The Garrett -Wade catalog has a PVA glue that it claims:
1) It fills gaps with strength
2) Squeeze out does not penetrate the wood and easily chips off when dried,
no need for scrapping.

I wonder how it holds a joint together if it "does not penetrate the wood and
easily chips off when dried"?

When fresh glue is directly applied to a surface it has maximum
ability to 'wet out' the surface and achieve optimum adhesion.
Adhesion will normally be a combination of chemical and mechanical
properties.

Squeeze-out will never yield optimum wetting and therefore adhesion.
The fact that squeeze-out doesn't penetrate the wood and easily chips
off when dried doesn't really tell you much about the adhesives
properties where properly applied.
Wally Goffeney
http://mywebpages.comcast.net/wgoffeney/index.htm

Michael Williams said:

Roughing the surfaces, as most glue manufacturers recommend, exploits
this aspect.

Do any wood glue manufacturers recommend roughing the wood? The wood
should be planed smooth to achieve the strongest joint.
--
Mac Cool

Depends on the glue and the wood. Actually, I was thinking of non-porous
materials when I wrote the quoted text--forgetting the context of the
thread. Most wood glues work through 'wetting'-- the glue penetrates
several cells deeply in the porous wood, forming mechanical (interlocking)
(and also chemical) bonds. Thus smooth well mating surfaces are optimal as
clamping then very effectively helps force the glue into the wood. A
uniform thin layer is desirable. Machine and tool marks obviously diminish
this and create distinct pockets.

With very dense, oily wood, porosity is minimal. The story is different.
Epoxies do not depend on deep penetration and require different preparation.
Slightly roughing the surface is sometimes desirable; see for example,
http://www.glen-l.com/supplies/pxman-use.html.

I think I will say no more having already fallen into the generalization
trap. Mr Ruttan's suggested reference,
http://www.fpl.fs.fed.us/documnts/FPLGTR/fplgtr113/fplgtr113.htm is a good
one indeed.

-mw

On 6/30/04 10:57 PM, in article , "Mac
Cool" wrote:

Michael Williams said:

Roughing the surfaces, as most glue manufacturers recommend, exploits
this aspect.

Do any wood glue manufacturers recommend roughing the wood? The wood
should be planed smooth to achieve the strongest joint.