I go out to my car yesterday morning, and the windshield has a 6 inch crack in it. I drove the car an hour earlier, and there was no crack. It's rather obvious, so I don't think I simply failed to notice it. I did not notice anything hitting the windshield either. There's no ding in the windshield, only a crack. This morning the crack looked longer. Not sure if I was imagining it, I marked the windshield with a sharpie. A few hours later, the crack was 1/2 inch past my mark.

Will it stop? Or will I need a new windshield? And how did a spontaneous crack develop in the first place?

I've heard of companies that fix cracks. Do they really fix them, or just stop them from growing?

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Unseen factors don't make it spontaneous
Temperature changes can work on an existing flaw until it finally gives too.

Windshield repair is normally an epoxy that fills the crack and makes it very unnoticable.

I've never seen a repaired crack keep craking- that doesn't mean it doesn't happen.
Many folks will drill a tiny hole at the end of the crack to stop it from spreading.

It's normal for a crack (at least the unbranched kind) to show little or no growth for a long time and then suddenly get a lot longer all at once. It happens silently, too. I've had it happen while I was right there driving, and didn't know it until I looked down again and saw that the crack was longer than it had been a minute before, after days or weeks of no change. It happens most of all when the weather is cold and the defroster is going.

A single-line crack will eventually grow to extend from one edge to the other, leaving you with two adjacent pieces of glass where one was meant to be, but that doesn't mean it needs to be replaced unless:
1. The law calls it an obstruction of your view and it would fail the next inspection;
2. You decide it's an unsafe visual obstruction yourself, or just don't like seeing it there; or
3. You think it's introduced an annoying new rattling/buzzing sound to your car.

If none of those three things apply, you can just drive around with a two-piece windshield.

I've had two windshields in a row get linear cracks, one just before I ditched the car anyway, and the other windshield has been replaced. In the latter case, for the final few days when the crack was at its biggest before removal, certain parts of my music started to have a buzz/rattle accompanying them, and I think it's because of a resonance effect from the fact that the glass was splitting. (...not necessarily the glass itself vibrating; it could have merely affected resonating behavior of some other part, like in the ceiling, especially with the motorized sunroof).

The desk guy/cashier/receptionist at the place where I had my windshield replaced told me that even linear cracks must begin with an impact with a rock or something like a rock, even if you don't see an impact point with a divet or a web-effect. Growth after that is another matter because it can progress spontaneously, but they all have to start that way. But it can start so small that you might not know it until days later when you see it for the first time.

ive seen a crack on my moms windshield spread about 7 inches one time. it was pretty cool watching it.

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I wish I could share your enthusiasm

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Back in the winter of 2002/2003 it was bitterly cold - often -20* F during the day, or right close to it, during a two week period in (I think) February. I was working at Dartmouth, and just got off shift in the afternoon. I went to get into my Sundance, and when I shut the door the back glass shatters into a thousand little pieces. I didn't notice a crack in it, but when it shattered I watched as the cracks originated from a central point of failure and quickly spiderwebbed out. Sucked majorly, but insurance covered it under comprehensive.

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"4th Law of Modern Thermodynamics: Where Mihoshi is, Chaos Reigns." ~W. Hakubi
"Gun control is hitting your target; Recycling is reloading your brass." ~ Lex of Dirty Work.

A small crack (Less than the length of a dollar bill) can generally be repaired. Very cheap (my particular insurance company covers it for 100% of cost, no deductable, if you have comprehensive coverage). If you let it go until it gets longer, then the only fix is to replace the windshield. Still relatively cheap (compared to body work or something), but is now between $200-$400 (in this area anyway). At that point, we don't cover your deductible.

Obviously insurance varries based on company/state/and coverage you carry. And prices probably vary by location. But the moral is, get it fixed while it's a cheap and easy fix. Otherwise it becomes a more expensive, and less easy fix (and a good number of people who have had their windshields replaced end up with less than ideal seals that let in drafts, make noise, etc...that's a very common complaint when a total-replacement has been done).

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I'm like one of those idiot savants...well, except for the savant part.

Theory of Zombie Relativity:
1) Everyone Else is a Zombie relative to You
2) Whether or not it matters is related to the inverse square of the distance between their teeth and your brain
(Quoted from Demigrog)

Our state typically has a $50 - $100 deductable on auto glass replacement. Most of the auto glass companies take advantage of this and offer to pay your deductable for you.

After one particularly hot summer day - I returned to my parked car after a day at work and found my rear window completely shattered into bazillions of tiny pieces. Needless to say - that had to be replaced. Didn't cost me a dime. I didn't find any foreign object to explain it so I can assume then that the heat was at least part of the issue. If a passing car threw up a small stone coupled with the pressure build up in the car - that would explain my experience.

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Spock Jenkins of the Vulcan Jenkins'.

Once when I was a kid, back in the dark ages when spectacles' lenses were made of actual glass, I had a lens shatter spontaneously. Very strange sensation, as you might imagine.

People thought I was lying -- that I'd dropped them or something. Nope, it happened with no warning or apparent cause, when they were on my face. A day or so later I rubbed my eye and a shard of glass came out.

Glass can do that. Internal stresses build up, and then one day, pow!

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"It is quite clear that Occam's razor does not sharpen in your pyramid." (Nicolas)

"Still, a man hears what he wants to hear and disregards the rest." (Paul Simon)

My dad painted office windows and doors with gold leaf...Attorneys at Law...etc, so he worked with glass a lot. If you take a glass cutter wheel, and etch slowly a "T" at the endpoint of the crack, the relief in the stress will sometimes arrest the propagation. Say the crack runs three inches "west" across your window...start the glass cutter wheel about an inch below "south of" the current tip, and just"west" of it, and score it upwards slowly till you're about an inch "north" of it. That'll usually hold the event until you can repair it. The crack reaches the score line, and makes a perpendicular jaunt, terminating. Works in glass greenhouses where wind can cause stress fractures, and repairing is far more conveniently done in fairer weather. On a vehicle, you can't obstruct view, but elsewhere, tape strengthens the joint, too. ...and safety glass in vehicles makes the T less effective. pete.

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A third rate theory forbids
A second rate theory explains after the fact
A first rate theory predicts...A. Lomonosov

I've had the windshield defroster cause the glass to crack when it was about -30C.

Last week a crack developed overnight right across the bottom of the windshield from where a stone had hit it almost two months earlier.

But the most awesome glass-cracking I've witnessed was when my pick-up was rolled last year. As the roof above the windshield caved in from left to right, I watched numerous cracks eminate, also from left to right, from the top of the windshield. Hope I never experience that again.

Yowza!

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Bring back Firefly!

"It is quite clear that Occam's razor does not sharpen in your pyramid." (Nicolas)

"Still, a man hears what he wants to hear and disregards the rest." (Paul Simon)

I highly, Highly, HIGHLY recommend AGAINST doing just this. I did this to my own windshield, convinced that it would stop a crack from growing up my windshield. Instead of going up, it branched out, and now crosses the lower half of my windshield. Almost all the way across, both ways. I took a 4 inch crack and extended and redirected it to a few feet total. Not a good idea!

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You can stop-drill glass, but I'd use the drill bits made for glass. Regular drill bits can catch the edge and now you've got twice the crack!

Do fill it in with epoxy then use progressively finer grades of sandpaper before moving to glass -polishing compounds (such as red rouge).

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Perception isn't reality. It's merely an abstraction thereof, and quite often not a very good one at that.

I am human. Fully human.

Uhhh.... Would did you drill the hole with?

A .22?
Although Fazor may also suggest a cod, sock, or a spork.

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A glass bit. Picked it up from one of those fix-your-own-home places. The crack didn't spread immediately, mind you. It was fine for a few days, until there was a snow-on-the-windshield-but-the-heater-is-running thermal conflict moment. I was driving to work, and I hear a BANG! BANG! BANG! I look in the rear view mirror, thinking I should see my muffler rolling along behind me, or my transmission or something. Then I notice the crack growing laterally. Over a period of three days, it went from a little 4 inch crack starting from the bottom, to a crack spanning almost the entire width of the windshield.

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I don't get the link...


Really strange... Do you know anyone else that had an experience like that?

Operationally, or the joke? It's about using strange things to drill holes. Kind of a dry reference, but I couldn't get the picture out of my mind.

Anyway; I've tried it once too, to no avail. But, I cant remember the type of bit I used.
I've also tried windshield repair kits to no avail.

Since then, I've learned to spend a bit more money to maintain my vehicles... So now I either live with it or replace it.

I haven't seen anyone mention about mounting flaws. I've heard that many of the cracks may be from bad frames, dirt in the mounting, or even a hidden, latent, manufacture flaw in the glass

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