Windshield delamination discussion

DuaneEstill

Banned User
It's a good idea for this community to have 'received views' about certain things, and I haven't seen this one discussed just endlessly, and I was wondering myself actually. IT's healthy to discuss these things as a point of reference for any future potential issues.

Two established members of the community were in a disagreement, one being a seller of NOS windshields and the other being a master mechanic and experienced with industry standards in windshields.

I've bought approximately five windshields between the spiders and X's I've owned and I always hated delamination for purely cosmetic reasons, and the dreaded "smokey glass" thing we've all seen.

The one position was that delamination, in any form, compromises the structural integrity of the windshield to a significant point. The other position was, "Hey...it's a 30 year old car too, and a little delamination isn't going to matter in the larger context." (forgive me if I haven't presented the views well enough here, and this is not to stir anything up)

I do recall discussion that the windshield on an X, but not a Spider, is a stressed member of the carriage, ergo, that's why they're so hard to get out. And remember too that the X has a uber-stout cage to begin with, so we're still pretty darn safe even compared to modern cars. Spider windshields almost fall out/off.

I'll go on record as having bought many with minor delamination and would do so again, but if new one's are available and reasonable I'll buy new. When I'm in an X and thinking of the potential problem areas that could become extenuating, delamination isn't near the top of the list, but it isn't at the bottom either.

To me, the critical question is "How much delamination is going to be structurally significant on an X in the event of an accident?" or "Are there peripheral issues related to delamination?" Like....the windshield falls out or something.

Interested to know what other's think.
 
Size question

Are there size/shape differences between years? Will someone who produces a windshield for an 80 be able to fit it into an 85? Might help to narrow down choices...

Answered...
Matt at Midwest-Bayless sells windshields for year fit of 74-88, so I guess that answers my question.
 
funny

can't find the original thread to see what was discussed.

here's my view if you want to know about
transmissions = Steve H.
wiring stuff = Bob Brown
Windshields = Tommy
Sellin stuff = JJ
 
Notice the years

74 to 78 don't seem to delaminate, not sure why, but 79 and on do.

Depending on how much the car sits in the rain will affect the amount of cloudiness. My 79 has a bit at the bottom of the glass, but over the winter the area on the bottom of the glass becomes clear again. Wash the car a few too many times and the clouds are back again. As for strength, not even going there but appearance is an issue to me anyway.

TonyK.

Grimsby Ontario Canada
 
When I have the time to elaborate

in greater detail I will, if the "short answer" does not suffice. If ya need or want more specific details, just ask.

Just to clarify, though, I am a Certified Master Auto Glass tech, not a Master Mechanic. Although my thoughts and views could be considered mere opinions, they are educated opinions based on over 20 years of handling automotive and aircraft glazing products. Things change and improve all the time, so the question of what is "OK to use" or "best to use" are actually nothong more than "value choices". To make the best "value choice" I think you need the most accurate relevant information you can find.

OK, as to the question of should you buy/install a windshield that has any delamination, the "short answer" is NO -- UNLESS there is no other option and the windshield you have is smashed and/or you are facing fines (because some states have laws for cracked windshields. I can explain why that is the case too, if you really need to know). Even then, I would only do this as a temporary measure until a newer non-damaged part could be found.

Here's why: The factors that caused the delamination in the first place have an effect on both the glass and PVB (the clear lining) components that make up a windshield. This can lead to the glass becoming more brittle as well as diminishing the bonding capacity of the PVB. I've seen evidence of delamination-weakened windshields being knocked out of a car - leaving behind a very sharp rim of jagged glass from the inner sheet that remained bonded to the urethane.

Several factors can cause delamination, but in older windshields it's likely a result of moisture (read as dry rot of the PVB layer), extreme temperature variance, and/or constant UV exposure. Glass and PVB are not immune to the effects of oxidation and UV breakdown, although it does take time.

The glass off a windshield is not tempered like the door glass. It's just plain old plate glass, and it's rather thin and flexible prior to being assembled, shaped and bonded. The lining between the two sheets of glass is made of Polyvinyl Butyral and you can learn more about it's properties on WIKI and other similar sites. The PVB layer is what gives the windshield it's strength. Without it, the glass would break into large fragments with very sharp edges.

Fast forward to construction/installation differences. In the past, the job of the windshield was to keep stuff (like wind:p) out of the car while giving you a clear field of vision. In today's cars, the windshield is an important part of occupant protection in the event of a crash. It has to be able to withstand the impact of an airbag (combined with the transfer of force applied to it from a sudden stop which in the past would cause gasket-set windshields to pop right out). It is also an important component to frame rigidity and roof crush resistance. All windshields made today meet these standards, and even if a 30 year old windshield may have met the same standards 30 years ago there is no way to know if it still would today - not worth the risk in my professional opinion.

Bottom line here is that a new windshield made to AS1 standards far exceeds a 30 year old windshields made to the highest standard of the time. As far as bonding goes, the only method that will ensure that the windshield will not come out in an accident - even a rollover - is using a urethane system.

Another way to think of this is would you put 30 year old tube type NOS bias play tires that only had a little bit of dry rot cracking on the sidewalls, on your car ? I sure wouldn't, especially when there is good supply of reasonably priced alternatives. But then again "value" is an entirely subjective thing.

Of course, the windshield may not seem to be as critically important to safety as tires are. BUT, if tragedy happens and you need it to be that critical, any perceived value of going with the cheapest option for both the part itself and the quality of the installation will be lost.

It's kind of like buying insurance in that you really don't like paying for it and hope that you don't need to use it, but when you do need it, you are glad that you have it.

Another extremely critical issue is that UV light can breakdown the bond of the urethane in a relatively short period of time. Installation should only be done when the trim ring will be reapplied at the same time. Alternatively, a urethane system that uses black primer (sika) will afford UV protection.

Tommy
480-250-3142
 
Last edited:
Flutter-flutter-flutter...

...the sound of pigs flying.
A miracle akin to parting the Red Sea.
Kudos to Duane.
 
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