Glue for veneer

[jteneyck]

Here's a glue properties comparison chart I put together from available data.  The data should be consistent within manufacturer, but there's no way of knowing if they are from one manufacturer to another.  

John  

[Juss1]

What’s the difference between open and assembly time? Is adding clamping pressure part of assembly time?

[jteneyck]

What’s the difference between open and assembly time?  Is adding clamping pressure part of assembly time?

I think open time is the time you can leave the glue on a surface before placing it against the mating surface.  Total assembly time is the time before you need to have clamp pressure and includes open time.  

A comparison from Woodcraft:  Link

John

[Bill Tindall]

What’s the difference between open and assembly time?  Is adding clamping pressure part of assembly time?

The chief chemist at Franklin(Titebond parent company) and I had a nice chat on this topic some years ago.  It was his opinion that these names should never have times associated with them, but marketing overruled him. 

When the glue surface is exposed after application to wood water begins to evaporate from the surface.  After some unpredictable amount of time, dependent on temperature, humidity, air flow and maybe other factors, the surface will begin to dry.  If the surface gets too dry it will not bond to the surface it needs to bond to to make a successful joint.  The glue must wet what it is bonding to to get a strong joint.   At most "open times" published for various formulations should only be used for comparison.  Actual time can vary substantially from what is published.  

"Closed time, assembly time or working time" is the time one has for moving the parts around after assembly.  This time depends mainly on the moisture content of the wood and the thickness of the glue in the joint.  Low moisture wood will suck water from the joint faster than wetter wood.  Once the water content of the glue reaches some low critical value the joint can not be moved without destroying the bond.  

A tip:  A property of adhesives like Titebond is that they have huge impact strength long before they acquire much shear strength.  We can take advantage of this fact.  A mortise and tenon joint that has seized prematurely is immune to further pounding(impact) it together.  However, steady pressure (shear) from a clamp will slide the seized joint together effortlessly.  I take advantage of this property every time I assemble a dovetailed case, for example.

[jteneyck]

The chief chemist at Franklin(Titebond parent company) and I had a nice chat on this topic some years ago.  It was his opinion that these names should never have times associated with them, but marketing overruled him. 

When the glue surface is exposed after application to wood water begins to evaporate from the surface.  After some unpredictable amount of time, dependent on temperature, humidity, air flow and maybe other factors, the surface will begin to dry.  If the surface gets too dry it will not bond to the surface it needs to bond to to make a successful joint.  The glue must wet what it is bonding to to get a strong joint.   At most "open times" published for various formulations should only be used for comparison.  Actual time can vary substantially from what is published.  

"Closed time, assembly time or working time" is the time one has for moving the parts around after assembly.  This time depends mainly on the moisture content of the wood and the thickness of the glue in the joint.  Low moisture wood will suck water from the joint faster than wetter wood.  Once the water content of the glue reaches some low critical value the joint can not be moved without destroying the bond.  

A tip:  A property of adhesives like Titebond is that they have huge impact strength long before they acquire much shear strength.  We can take advantage of this fact.  A mortise and tenon joint that has seized prematurely is immune to further pounding(impact) it together.  However, steady pressure (shear) from a clamp will slide the seized joint together effortlessly.  I take advantage of this property every time I assemble a dovetailed case, for example.

As an engineer, I understand where the Titebond chemist is coming from.  A definitive answer in with respect to glue open, set, etc. time is impossible to state.  On the other hand, customers want and deserve guidance on how best to use your product, so you have to publish something.  I find the times listed by Titebond to be overly generous with the wood and amount of glue I use, but at least I know that TB Original is going to set up faster than TB III - and it certainly does.  

John