As previously posted, this morning I made highly unusual for me early morning trip to Hart Acoustical and got 7 tubes of OSI SC-175 acoustical caulk, which is the same kind I got to seal around electrical outlets in Lyndhurst. Or at least same label, I wonder because when I previously investigated the ingredients in early 2012 I thought that the principal component was a Melamine resin, which btw I think is fine unless you're drinking it in your milk... But now I no longer see Melamine listed, it has an Latex base, with some typical caulk ingredients including the ultra low VOC plasticizer oxydiethylene dibenzoate (hereafter called OD). I must have been wrong about the Melamine, or perhaps they've just renamed to same stuff "Acrylic" which can cover a lot of ground.
(Update: I applied a significant amount of the new caulk on Sunday night to re-seal some gaps left by Tom. This does not seem like the same stuff. This SC-175 is smellier and less stiff than what I used last time. I preferred what I had last time. However, evidence suggests that SC-170 is not what I used last time either. The OSI website now does NOT show either SC-170 or SC-175 as a Melamine caulk. I wonder why I believed that last time. SC-170 is solvent based, needs to be cleaned with minerals spirits, but SC-175 is latex based and cleans up with water. That would pretty strongly suggest that SC-170 is smellier than SC-175, not the other way around. That wasn't true last time for sure, I used only water and did lots of clean up. So the more I look at this, the more confused I get. One possibility is that what I got last time was very old tubes of SC-175. They were sufficiently old to have gotten slightly stiff and lost the smell. BTW, I don't trust my very own words in this blog a year ago saying that I was using SC-175 last time. I might have just said that because I then didn't want to create perception that what I had used was better than SC-175 because I hadn't tried the other one. So last time I lied to protect the unknown. Show how much faith to put in this blog. But at least it wasn't for pecuniary reasons.)
I didn't get Green Glue sealant because I'm not aware it is available in any local stores. And actually, the OSI SC-175 might be more useful for big cracks anyway, as it's more viscous, almost solid, when applied. (Not as solid as last time, unfortunately, and Tom's attempt to seal the big 1+ inch gap behind the baseboards was full of gaps, only some of which I had time to seal. Once I tried using the new tubes myself I could see why. To re-seal some of these gaps I had to use a float-like technique which was very messy and time consuming. No builder is going to do things that way for production work.) I'm only a little less sure of the ingredients in the OSI product. The Green Glue Sealant is basically just latex. The OSI product is more like typical acrylic latex caulk with mass adding ingredients for acoustic performance and OD added for permanent flexibility. (And unfortunately lots of ethylene glycol as solvent.) FWIW, it's also probably the cheapest product in the acoustical caulk category, which may explain wider availability.
Here's a great discussion of acoustical caulks and substitutes like plain old 50 year caulk.
OD does not appear to be particularly harmful in normal usage. According to this MSDS, it's a negligibly low VOC plasticizer...just the thing for permanently flexible caulk. It is not known to be or reportable as carcinogenic by the State of California (this is a correction, I first read the MSDS wrong, but it does use a disclaimer invoking federal law as it applies to the California law--perhaps just standard boilerplate, perhaps not). I believe now it is similar to lots of stuff we are surrounded by, fine unless you're imbibing it directly. Mostly, it just stays in the product, nearly forever, or so I hope.
I'm not worried at all about my exposure to the silica and quartz in the caulk, though these account for most of the wording in the MSDS. Once applied, those ingredients will most certainly just sit there. We live in houses built upon and sheathed inside if not outside with silica based products after all. You get far more silica exposure messing with mud, for example, than caulk.
Anyway, I didn't much of this left over yesterday, and Tom was convinced that the wall-to-ceiling gaps should be mudded, not caulked, for better appearance. Now I see I could have insisted that he used the caulk behind the mud. That is the recommended acoustical practice--if you need the mud at all. If you don't need the mud (to make flat visible surface) you should just use the acoustical caulk, as it has dampening flexibility. But that would have taken two days just for the sealing, and I didn't have any significant amount of acoustical caulk yesterday, having using up countless tubes earlier this year for sealing the soundproof wall door jamb for the Queen's room.
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| What the SE corner looked like yesterday |
And despite saying yesterday that he didn't think any caulk would fill the baseboard gaps which go up to 1 1/2 inches, today Tom went ahead and started applying the caulk to the smaller gaps around the critical SW corner of the room--where the subwoofer sits. The he decided the stuff was thick enough to use all round the floor of the room, which he did. I was very pleased! Just as he came to break the news to me, I was reading online about how it was best to use only acoustical caulk if possible, then mud on top for appearnces sake if necessary. Tom used 3 tubes today. The caulk will be covered by the baseboard so appearance isn't important, only coverage.
Tom also painted the ceiling with Behr Premium Plus Flat Ceiling Paint which he picked up when getting his lunch. He checked out the can previously used in the Queen's Room so he would know what to get. As posted earlier, I'm sticking with Behr Premium Plus for all interior work now. Tom used a sprayer and sprayed from multiple directions he told me. He also told me it was best not to pre-clean (that would loosen texturing) or use a roller (that would shred texturing--an experience I had when first painting most ceilings in this house...21 years ago!!!).
After the painting and caulking there was noticeable (though not intolerable) smell in the room. I opened a window after he left but seeing the gathering storm clouds closed it shortly thereafter and opened kitchen room (where I have been since) instead, though I don't smell any caulk in the kitchen.
Already, with the new mudding and caulking, the room seems more isolated from outdoor noises, the wind and barking dogs, in spite of the fact the room is nearly empty and is hugely (though nicely) reverberant. The reverberation dies away uniformly which is nice...no audible post-echoes.
So I think the room sealing has been a big win.
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