I am finishing up building a music/film-editing studio, and one of the final steps of construction (before I start appointing the interior and gadgets) is finishing the walls… which is to say, finishing the acoustic enhancement to “typical” walls. This involves two layers of 5/8” drywall with a special layer of “magic” in between.
The magic is called Green Glue. The name is a bad choice (Green Goo, perhaps… or maybe Oobleck, if they could get the rights from Dr. Seuss), because it’s not glue at all, and this seems to confuse a lot of people. You can’t use GG to adhere the two sheets of drywall. It doesn’t work anything like construction adhesive (i.e. Liquid Nails). This actually comes up quite a bit in forum discussions, but the fact of the matter is that if you used Liquid Nails in the same way you would Green Glue, it’s likely that your acoustic dampening would actually be reduced instead of increased. Liquid Nails becomes rigid when it dries, so it is possible that it would simply turn your wall into a giant drum head, actually increasing reverberation and reflection (no absorption of sound waves, and instead more reflection).
Green Glue claims that their product converts vibration into heat. It remains flexible, and thus absorbs sound waves/vibration rather than allowing them to reflect back or transmit through the wall material.
My research regarding Green Glue actually began with this “why is it any different than Liquid Nails?” question –I was wondering if I could use Liquid Nails in the same way one would use Green Glue. You can sift through hundreds of pages of third party technical data like I did, or, you can go the quick route and take my word: Green Glue is worlds apart from Liquid Nails. If Liquid Nails was an elephant; Green Glue would be a Blue Heron (or perhaps a slug, considering the sticky goo factor).
After deciding that Green Glue was worthwhile (and worth the rather high price when compared to Liquid Nails, which, again, is not even REMOTELY similar), I ordered a 5 Gallon bucket of the stuff from Amazon… probably a mistake. I highly recommend going a more direct and productive route. The attention and specificity you will get from someone who knows what they are selling (like Ted White, co-founder of Green Glue, now owner of The Sound Proofing Company) are worth their weight in gold… and you will actually get a BETTER PRICE on what you need (not to mention complete and detailed instructions, vs. just a bucket in a box). The only downside is you have to actually communicate with a human. The Sound Proofing Company won’t sell you anything until you fill out a little online form telling them about your project, and then wait for someone to get back to you. Not a good system for impatient people who don’t like talking on the phone –like me (which is why I ordered from Amazon before realizing the above route might be better).
I paid $215 plus $15 shipping for the 5 gallon bucket on Amazon. Ted tells me he sells a 5 gallon bucket for $198. Here’s the kicker though… on Amazon, the special applicator (a 32 oz., specialized caulking gun called a Speedload Dispenser) sells for $56 plus shipping. Ted let me know his company sells the gun (which he helped develop) for only $29 (though their website indicates otherwise, so you’ll need to contact them directly).
I actually became acquainted with Ted because I was trying my damnedest to avoid purchasing that applicator. I didn’t want to “throw away” $60 on an applicator that I would use once and never again.
I was hoping I could use a trowel to apply the Green Glue, and this method is actually encouraged by several “licensed” resellers of the product. I can assure you, the guys who invented the glue and a bunch of other people who chimed in on the message boards get REALLY upset when you talk about using a trowel.
The consensus is that you are supposed to use two loads of Green Glue from the Speedload Applicator with the tip cut to 3/8” and a bead applied in a spaghetti type pattern. PERIOD. No other application method will deliver the desired results. I’m serious, guys. The people who claim to know the most about this product will get REALLY PISSED OFF if you try and go any other route (I got pretty beat up on several message boards). Seriously. They get really mad… which is weird, because the manufacturer of the product and many, many other official resellers say it makes NO DIFFERENCE whatsoever what pattern you apply the glue, and also what thickness of bead should be used.
For what it’s worth, the written materials that come with the tubes tell you to cut the nozzle to 3/8” and apply one load in one direction and the second load in a perpendicular direction (no mention of spaghetti or any sort of randomness). The Speedload Applicator comes with nozzles pre-cut to 3/8”.
The literature that comes with the applicator also clearly states: “…Lines, squiggles, plops, etc. The pattern isn’t an issue, it’s the amount being used. The Green Glue needs to be roughly even across the board.” They even show one example pattern that is extremely uniform… which supports the use of a trowel. And one of the photos of the application shows Green Glue literally just “plopped” onto the drywall.
The “makers of Green Glue” (the people now running the company) could clearly care less about the application pattern of the product. They also think 1/4” is fine for the bead. Or 3/8”. Or whatever. Another site, SoundIsolationStore.com, says: “A larger tip opening on the nozzle to speed up application will still yield the same results as applying Green Glue Compound with a smaller bead.” They go on to say: “No specific coverage pattern is necessary to ensure excellent results. Apply at least semi-evenly over the correct amount of square footage per tube and you will succeed.”
This YouTube video DIRECTLY from Green Glue Company, LLC (“copyright Green Glue Company, LLC 2008”) shows a person “spooging” Green Glue onto drywall in streams and globs. Not the spaghetti technique. Not the two directions technique. And very much NOT a uniform bead of Green Glue (anywhere from what looks like 1/4” thick to maybe nearly 2” thick).
This video directly from the Green Glue Company website regarding installing GG with the speed gun applicator from a 5 gallon bucket says you should cut the nozzle to 1/4” (not 3/8” like I was told is a MUST). It should be noted for shits and giggles that the hole the guy cuts in the nozzle in the video looks like you could drive a truck through it. This video directly from the GG website regarding installing with 28 oz. tubes also says 1/4” (not 3/8”). Both videos show the person applying a straight line “2 to 3 inches from the edge” all the way around the perimeter of the drywall sheet before treating the rest of the board. The “5 gallon bucket” video also says you should pull the plunger on The Speedload Applicator 2-5 times before starting in order to lubricate the gun, but makes no mention of adding any lubricant. To my knowledge, the guns don’t come pre-lubed, and in fact, the instructions that came with mine make a rather lengthy point of how to add WD-40 at various places to lubricate the gun before beginning. This 5 gallon bucket video also notes that one tube of GG is only about 70% as effective as two tubes. Both videos go on to say “the application pattern does not matter so long as you have distributed the compound evenly across the drywall.” I got SO MUCH SHIT on various discussion boards for asking WHY the spaghetti pattern was the only way to do it. (Also, the idea that the application pattern doesn’t matter leads me to believe that applying with a trowel is totally fine). The video also says that no treatment of the first layer of drywall is necessary (I mudded all the seams on my first layer, and I don’t regret spending the extra time), but that the second layer should be staggered (to overlap the previous layer’s joints). Finally, they recommend a quarter inch gap is left between all edges of your second layer of drywall so you can apply acoustical sealant –but then make no mention of whether or not you are supposed to mud over that, or if you then just paint the “acoustic goo” sealed seem, which I can only assume would be extremely obvious looking (not a “finished” look). [UPDATE] From SoundIsolationStore.com: “Step 4. Seal Your Wall Once the topmost layer of drywall is attached, seal the wall thoroughly using Green Glue Sealant or a comparable high quality acoustic caulk. Tape and mud your seams as you would normally do, and prepare for your wall finishing.” If you have staggered your drywall so that the top layer seams are flush against a solid piece of drywall (not lined up with the lower layer seam), I’m not sure why this would be necessary, but it is what it recommended. The literature that comes with the Speedload Applicator says, “Dedicated high performance rooms such as recording studios and theaters often specify the use of acoustical sealant in corners and along the floor. You can alternately use drywall compound to make sure all gaps are filled. The goal is to make the room has as air tight as possible. [sic]” It should be noted that the Speedload literature also goes so far as to say THEY DO NOT RECOMMEND taping and mudding the first layer of drywall.
NOTE: All videos and literature say you need to apply the drywall with screws within 15 minutes of applying the glue.
For what it’s worth, I still think there’s merit to the trowel method if you are applying Green Glue in cooler temperatures. I wouldn’t try using a trowel when it’s warm out or if it’s warm in the room (the GG will be too viscous), but when my studio was at 50 degrees Fahrenheit and the product was much thicker and tackier, the GG spread perfectly with a trowel (see photos below). A 1/4” tooth would be perfect for Green Glue’s recommended bead size, and applying it in two opposing directions seems like it would work great. It’s not a totally random pattern, but according to Green Glue, that really doesn’t matter.
Ted White says Green Glue needs to be applied at around 70 degrees Fahrenheit for proper compression, and while I believe him (especially since he was around for all the testing of the product), the literature that comes with the glue and on the GG website makes no mention of this. Somehow the temperatures here in Colorado reached 70 degrees Fahrenheit this January (no kidding!), so I ended up using the Speed Gun Applicator, but had the temperatures remained cold, I would likely have spent less time trying to bring the ambient temperature of the studio-under-construction up to 70 degrees, and would have gone with the trowel (ESPECIALLY since the Green Glue site and many others say the thickness of the bead and the application pattern are both completely irrelevant as long as you use the correct amount and get even coverage).