How to properly spread green glue

#1

Hi

Thanks for the help in the other thread. I am ready to move forward. I have the green glue, and have a Q about how to properly apply. I watched this vid:

https://youtu.be/RLtlcy5YDQM?t=67

It seems as tho the entire are is not covered. I assume it will spread out when the two panels are pushed together... but won't there still be small pockets of no glue? Is it not better to use a scraper to lightly scrape the glue over the entire area?

Thanks!

#2

Those small pockets are part of the system, and they are supposed to be there. Green Glue is not glue at all: it is not an adhesive, and is not meant to hold the panels together. It's entire purpose is acoustic. It is a visco-elastic polymer with specific properties that help it damp vibrations between the panels, and in vibrations moving through the panels. The random arrangement of the strings of green glue and the gaps between them is an important part of how it works. You do not want the panels to be tightly stick to each other... rather, you want the gunk to create a very small separation between the panels, so that they don't really touch each other. Also, the compound never really dries, and is not supposed to dry or harden (like normal glue would). It remains "tacky" and rubbery forever. I really wish they would not have put the word "glue" in the name, because it misleads people into thinking that it is an adhesive, and should be used like one, but that isn't the case. So just squirt out those strings of gunk randomly over the back surface, in swirly patterns, exactly as that video shows. One or two tubes per full panel of drywall (4' x 8') is about right. Don't spread it out or flatten it, or use a spatula.. just do it like they show, and you'll be fine...

#3

Thanks Stuart.

Green Glue is not glue at all

I know!

So, you want a gap between layers of sheetrock, ok that makes sense. But what doesnt make sense to me, is not having full coverage of GG on the panel(s). The way my brain is working... it's telling me that the areas in between the panels not covered by GG will not stop vibrations; that vibrations will still move through the panels in those spots. And that ALL vibration would be stopped if the entire panel was covered. I guess I am wrong about this?

#4

Those gaps are air "springs", and also separate the panels, so they don't touch. It's rather complex, but as the panels flex and vibrate, you do NOT want them to act as a single, solid mass: you want them to act a bit independently, sort of "sliding" past each other at the microscopic scale. The random arrangement of the "glue" and the air gaps accomplishes that. Technically, the concept is known as "constrained layer damping", where the layers can move independently but are damped acoustically by the "glue", along with the air gaps. If the coverage was 100%, completely joining the panels across the entire surface, the constrained layer damping would not be very effective. Too much Green Glue would inhibit the damping at the frequencies that matter most. I wrote an article about Green Glue a few years back, that you might find interesting:
The truth about Green Glue

- Stuart -

#5

#6

'nother Q

Is it better if the two panels of sheetrock are touching, or not? I put up one panel, and then put GG onto the 2nd panel, and then nail the 2nd panel to the first. Now both panels are in contact with the GG. BUT - say I put up one panel, and then put GG onto the 2nd panel, not going all the way to the edges, and then put some rubber (?) trim around the perimeter of the 1st panel, so when the the 2nd panel goes up, the GG that is on it is not touching the 1st panel. Is that better? Or is it better to not have an air gap in between most (not all) of the panels?

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