Insul. glass fogging is chemical etch???
I asked this 2 years ago when I first posted here at the suggestion of FHB editors, got flamed by Gabe big time, nobody had an answer — my! hasn’t Gabe mellowed since, just about named myself “roadkill” for the new site.
Time again to ask again.
My hunch is if anybody could answer with chemical insight it is D. Thomas?? Prove me wrong somebody; David, any ideas?
This has been buggin me for 4 years, never have found any research on this, people I work with that have doctorates in chemistry have no idea what I’m even talking about.
Anyway, when you dissassemble* the “fogged” themopane glass from 30 years ago (made by Fentron in Seattle, Ar filled not available 30 years ago) to try to “clean” it, it isn’t fogged, it is literally etched with a pebble like pattern (verified by SEM comparisons to corona etching of electrical insulation). Pebble pattern is approximately 1/2 the granularity of a basketball “pebbles”, it is not at all similar to HF acid etch surfaces. Both tempered sliding door glass and regular windows exhibit the exact same pattern. What is the chemical reaction that produces this etch????????. A possible thought is that it is bacterial origin (David, ask your wife?) rather than simple straight-forward chemical. The original sealant was butyl on aluminum channel,1/4″ spacing, dark anodized chromic acid aluminum frame. Windows in INdirect sunlight(everything in D. fir shade 90% of day) appeared to be most effected. Thermal cycle excursions were likely never above 100 F to 15F (Seattle area).
Any insights appreciated as to the mechanism of etching.
Art B.
* heat gun and thin/sharp carpet knife work well, the ones I was able to “clean” & polish 4 years ago and reassemble with silicone and dessicant on cold clear low humidity day are still clear.
Replies
A Stab in the Dark.....................
The failed seal on the IG unit acts as a bellows with each diurnal temperature cycle causing moisture to be trapped and condensed between the glass.
The initial amounts of water are absorbed by the dessicants in the initial assembly of the glass.
When the dessicants are saturated then they are recycled into the envelope on a daily basis. Sodium silicate is a common inexpensive dessicant and when mixed with water to saturation will produce an alkaline solution of silicate, which will deposit (etch) silicate crystals on the glass surface through the daily cycles. Hence the "fogged" milky window look.
Just my theory added to a little chemistry knowledge.....................Iron Helix
PS............I admire your patience in repairing IG units. I could never find it cost effective, nor could I give my customer a warranty.
I was with you 'till the very last sentence: are you saying that the windows aren't realy etched, but have a coating that you can clean off ?
Phill Giles
The Unionville Woodwright
Unionville, Ontario
All: About 1/2 of the 39 segments in the house have experienced the etching.
Phill:
It is really etched. If you drag a knife point across it you can feel the surface. It cannot be cleaned. Diamond powder or rouge and patience will polish it smooth, but that's not worth the effort (even for me).
Gabe:
Acually, you've turned into a real softie. I take it as a sincere compliment that I'm in the running for being the "cheapest". I actually have started to spend some after both kids got their financial security from dot.coms (got out in time), so realized I'll never be able to spend what I've got given my financial nature. I actually did buy 5 replacement IG glass panels last year, but installed myself.
PS: Since you're a concrete guy, you may appreciate that I just finished mixing 6 yards concrete today in 3 cft mixer rather than getting "ripped off" for $56/yard. Reclaim sand/gravel here is even up to $12.20/ton.
Ken:
Good idea about possible acid residue from pre-assembly glass sheet packing, will have to ask chemist friends about that aspect.
Iron H:
The original windows did not have any dessicant, they supposedly were sealed with dry nitrogen accoriing to the mfg at the time. The first ones I fixed about 10 years ago with silicone I added dessicant to , no problems with those yet.
6 yards is 162 cubic feet, divided by 3 is 54 loads, times 15 minutes for each cycle and dump equals 810 minutes or 13 and 1/2 hours of work.
With material costs, loss productivity etc, you spent the value of 500 dollars to install 6 yards of inferior concrete with 54 cold joints that you could have had delivered and poured in a 1/2 hour for less true cost.
Like I said many times, no such thing as time being worth nothing.
It costs more in energy to use blades than to use an electric shaver and for some reason some people just don't get it.
:)
Gabe
If cost is the only criterion, why shave at all?
The real question is not what your time is worth in the cash economy, but what you'd rather do with your time. It's not hard for me to imagine that some people would prefer mixing and pouring concrete for 13 hours over doing something more lucrative but less enjoyable to earn the money to pay to have it done.
But then I bake bread by hand, probably inferior bread, with cold joints, so what do I know?
Gabe: concrete/razor blades a little off the window subject, but:
1. Agree on the shaving part, that's why I've a beard, no cost <G> BTW, wife cuts my hair.
2. Where else am I going to get the equivalent exercise - go to the gym and pay money to lift cast iron ?? Exercise is probably my best reason for hand mixing, plus there is a surcharge for less than 7 yards. I do buy truckloads for > 7 yards.
3. My cycle time is under 4 minutes when I start but slows down as the day goes on(not counting picking up material on way home from normal desk job Mon-Wed) , my dump truck backs right up to the mixer at same level, mixer dumps right into forms on this job - moved mixer twice, I measure both cement and reclaim by the shovelfull only, water not measured, about 2"-3" slump is eyeballed by slope of mix in mixer. Started at 6AM, finished about 2PM, sore tonight, first time I've mixed more than a yard or so in about 2 years.
4. Certainly do agree that this is way inferior strength to single pour (it sure ain't how we poured Minuteman silos in the 60s), but since this was only a foundation and floor for an outbuilding (which will likely get torn down for another set of vinyl monstrosities that are invading my area whenever I die or move) . I even went really cheap and used only approx 3-1/2 sack mix, used only free scrap metal & old unpainted pipe for filler/reinforcing, a quantity of big clean/wet rocks thrown in, etc, etc.
oh yeah- when I poured the concrete floor in my basement I didn't want to dig down anymore for headspace since the job was starting to get old. Being by the shores of the greatlakes I was in bank sand big time down there in the cellar so guess where I got my sand for the concrete. 5 years 4 inches and not a crack showing yet.
I have read about hard water "etching" fine crystal and window glass. Hard water can be caused by dissolved calcium carbonate and calcium oxide in the water. If I remember correctly calcium oxide is otherwise known as lime. The glue in concrete. It seems reasonable that if this was deposited by water and then it dried it might contract unevenly, stress and spall the glass at a microscopic level.
Does this sound right or do I need to adjust my dosage. Hmmm. Pretty blue happy pills. Sweet.
4lorn:
Best expl. and fit to observed facts I've heard so far, looks like a relatively subtle effect. A correlating factor is that the windows that are located between concrete columns* were the first to show the effect - 10 years ago. Also one item I forgot to mention was that there was a barley visible white film in places that came off with acetic or HCl acid, both of which readily react with Ca compounds, so there may have been Ca migrate in thru a seal break, dissolved in H2O.
*2nd floor is supported by 14 ea 12"by18" 3/4 wrapped rebar reinforced concrete columns - mixed and poured by hand, but a measured 7 sack mix, 2" slump and vibrated - designed for 9.6 EQ. .
Nitrogen + Water+ Oxygen = H2NO3 (Nitric Acid) ----??????
We need a Modern TO Date Chemist.............I'm years RUSTY.....................Iron Helix
Hi, Art-
Worked with glass here in Olympia for 25 years, also some work w/IGU's. I'm not much for chemical analysis, but I'll add a small tidbit to the discussion.
If I understand you correctly, the fog pattern is a 'regular' pattern similar to basketball pebble grain but about half the size. The only thing I have encountered like it has been when cleaning clear 1/8" glass. I noticed that the cleaning solution (ammoniated type), after wiping but before completely dry, had a residual pattern that seemed to match the pattern of the paper packing sheets (corrugated paper) that is sometimes used between the sheets of glass. Perhaps the packing sheets left a (acid) residue of some sort? The glass was not etched and I was able to wipe clear. Just a thought about possible residue and eventual interaction with H2O in a failed IGU. Of course if your glass units are that old, it is typical that they failed. Insulated glass was in it's infancy. Many IGU manufacturers now offer warranties because the process has been refined so much.
Sorry I can't give a better guess. Hope to hear any other ideas.
Ken Hill
I didn't flame ya, I said you were the cheapest person that ever posted............maybe not those exact words.........maybe it could have been a little harsher.......maybe it was a lot more direct.....I've mellowed as much as you've started to spend.
Gabe