The Stress Crack Myth

Bananas do not grow on trees.

Bats are not blind.

Duck quacks DO echo.

Bulls do not become angry at the color red.

Windscreens do not stress crack.

Bananas grow on something the size of trees, but the banana ‘tree’ is not actually a tree. The banana plant, which can grow up to 25 feet, is actually the world’s largest perennial herb. When you carefully inspect a banana plant, you’ll notice that it doesn’t have woody fibers. It has strong stalks and leaves, yet it lacks the trunk and branches that would qualify it as a tree.

Bats see in black and white. At night they see better than we do. They lack color receptors; but in low light, we can’t see colors either.

Duck quacks have no special sonic quality to prevent echoing.

Bulls and other cattle are partially color-blind; they cannot see the color red. They are, however, defensive creatures and will charge when threatened, frightened or annoyed.

Education is the debunking of mis-education. This includes spotting and correcting the many myths emanating from the internet, folk wisdom and word of mouth. We have all been taken in, at some point or another, by a modern myth. The countless ‘stress cracked’ windscreens returned to wholesalers as defects are, 99.9% of the time, rocking horse shit. There is usually an explanation.

Windscreens do not crack spontaneously. This cited phenomenon is usually attributed to bad or incorrect fitting. In some instances the crack will be emanating from an impact, and in some rare cases extreme thermal fluctuations can be a cause. The study of fracture mechanics does not accommodate for laminated windscreens which have, “cracked for no reason”.

Stress-cracked windscreens: a trade fallacy.

A Condemned Windscreen?

According to the repair criteria set out by a national and insurance ‘approved’ windscreen repair and replacement company, this windscreen is not eligible for repair:

Windscreen Front Elevation

Why?

There are too many chips.

Whilst the windscreen isn’t exactly peppered, there clearly are five areas of damage, but they’re spread out and well apart. Would the same company be happy to attend to the same car and windscreen on five separate occasions? We don’t know what their policy is and whether or not they have a way to monitor it, but anyone would think they would for sure. So what’s wrong with repairing all five in one sitting?

A closer look at each chip.

A:

It’s low down and by its position, size and type not intrusive. However, it is still visible. From the image it does look like it may even have had a repair attempted previously and the car owner confirms this is the case. In any case, if it has had a repair, it was a very poor attempt and looks like it can still be improved by re-repairing. The structural element of the damage looks untouched, and only the impact crater has been filled.

B:

This one is in the A Zone. It’s tiny. The diameter of a five-pence piece is 18mm. Some man maths-style deduction suggests the damage is between 3 and 5mm. The permitted repair criteria for an A Zone repair is 10mm making this a viable repair on all counts.

C:

Chip C, by coincidence is in the C Zone. The coin provides a useful scale and in any case, looking at the damage (before or after repair) is obscured by the rear view mirror so the emphasis here would be on how it looks cosmetically from the outside, provided it is repaired structurally. There is an obvious sign of moisture in the break, therefore no issue in why this cannot be repaired.

D:

Chip D. A classic ‘bees wing’ with some ‘daisying’ around the impact mark. It’s low down in the C Zone and repairable.

E:


Chip E is in the perimeter of the windscreen known technically as the D Zone. It’s a tiny ‘half-moon’ style break with more surface damage than structural. There are a couple of minute pit marks next to it which are easily addressed (sometimes referred to as vanity repairs).

Overall, four viable repairs and one re-repair. Chip A was not cited as a reason not to repair. The repair company simply said there are too many. How many car owners/customers would trust the word of a professional making such an appraisal and agree to have the whole windscreen replaced? The reality is, it won’t be long before the new windscreen (which would not be a genuine OE part) to pick up similar damage?

There are no ‘windscreen commandments’ forbidding multiple repairs, nor technical explanations (on the repairer’s website) to validate why their repair criteria is set in this way. Incidentally, they also will not repair anything in the windscreen perimeter yet they ‘proudly’ boast a ‘Repair First’ policy. So what’s the issue here? It’s quite plausible for a motorist to need five separate repairs on five separate occasions (which would obviously mean five separate invoices) but why is it that if there are four or five on the same windscreen they won’t repair on one visit?

Granted, some car owners would choose to replace the windscreen, so who decides? The consumer? But what if the consumer decides against it? A new windscreen? Who decides that? The repairer? Who is the real beneficiary here?

Windscreen Condensation.

Have you noticed that your windscreen is fogging up more than it used to? It may just be something unavoidable, or it could be something much worse.

First and foremost, water vapour in the atmosphere which occurs when your body heats the air inside the car – as does your breath – increases the amount of moisture it can hold. This means when it comes into contact with your windscreen (or glass) it cools and condenses, forming a mist. Simple. Nothing to worry about; it’s science at work. There are several tips (or hacks as they’re commonly referred to on social media) on how to prevent this such as:

  • Use the heater efficiently. Start the heater off cold, then slowly increase the temperature as the air dries out, rather than overloading the cabin with hot, ‘wet’ air.
  • Open one of the windows as you wait for the condensation to clear. The idea is that you’re not raising the temperature inside the cabin which will slow the process [of clearing] down.
  • Coat the inside of the glass with a recognised water repellent which will help prevent condensation.
  • Keep the windows clean. Keeping your windscreen clean will go a long way to stopping it misting up in the first place.

If you still experience excessive condensation, you could be looking at a much bigger problem.

It is still worthwhile noting that glass will mist up more in cold or wet weather. During the colder months the car windows might take slightly longer to clear; even longer so if it’s raining. However if you find that the windows continue to mist up to the point that the water droplets become bigger and more visible, the car is battling a water problem.

Where is the water coming from?

If you’re not bringing the water in on your clothes, or have left a door, tailgate or window open to allow the carpet to soak up rain, something could be leaking. The most obvious culprit usually is the windscreen. Next in line could be the sunroof (if the car has one) or the sunroof drainage; next in line: doors (drainage in the door) or the door membrane (between the door card and door. Some cars will develop a heater matrix leak and is much harder to detect.

Whatever the cause is, get it looked at as a matter of urgency. Driving a car with windows misting up is dangerous as well as illegal. You might argue the fine or even pay it if you’re happy to throw up to £1,000.00 down the drain, but crashing the car will cost you much more. Injuring or killing someone (because you didn’t see them in time) is unforgivable and it is not something most people can live with.

Always clear all windows before setting off.

Lockdown Defiance and Ignorance

Why are we, the British public, so defiant? Is it just us?

Yesterday I went to collect a couple of (pre-ordered) windscreens from a wholesaler. They’re doing all they possibly can as a supplier and this is immediately apparent as soon as you approach the front door:

ONLY ONE CUSTOMER AT A TIME

Also stated on the sign is a further request to use your own gloves, pen and mask. This message is on each of the four panels of the sliding door.

As I approached the door I saw there was a chap from another windscreen company busy collecting his order. I waited; as he came out I asked if he was done. He said, ‘yes’. My way in was clear. It’s a small reception area about 3m by 3.5m. A small serving hatch to the office and and a handover counter where the products are placed for collection. Customers usually go in, sign for their goods and wait for them to be picked from the warehouse.

In the time it took for me to be handed my invoice; sign it, and turn towards the ‘jump’, two guys walked in to the reception area. One chap, from National Windscreens walked straight up to the hatch and the other, from AVG, stood there like a lamppost making the third point of a triangle. “So much for the ‘one customer at a time’ notice on the door eh, chaps?” The fitter from National Windscreens just stood there like with a blank look on his face, akin to an envelope with no address on it. The AVG guy, stood in front of the door, ready to return my serve, “There’s two metres between us. I can’t see what the problem is?”

Therein lies the issue. We are given an instruction in the form of a request yet the general public ignore it and find a reason – a way – to justify why it does not apply to them.

Mr AVG fitter must have seen the signs; you can’t miss them because you have to walk through them to get it. Besides, he knew what I was getting at as he responded directly to it. He didn’t double-take and pop his bottom lip out. He knew exactly what he was doing. The rules did not apply to his sanctimonious self. Brave a supermarket sweep and you’ll see the same attitude and behaviour. Even before the governement update on lockdown restrictions, people were already dusting off their picnic hampers in anticipation of the rules being relaxed.

Is it just us, here in England? Other countries seem to be more respectful of such advice.

It’s Just a Windscreen

Image

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Whilst shaving the excess cured resin during this repair, the solar reflective coating became visible under the light in the workshop.

Layers of Reflection 3
Holograms

This particular windscreen is heated (embedded within the sandwich construction of the windscreen is a mesh of very thin heating wires which you will see in the image if you look closely; another more modern version of this is heated chemically via a silver/zinc oxide coated film within the glass).

Also within this windscreen’s layers is a ‘solar reflective’ coating (also known as solar reflective or athermic). Solar glass will allow sunlight to pass through it while radiating and reflecting away a large degree of the sun’s heat. This windscreen is also a HUD variant meaning it has a ‘wedge piece’ integrated within the PVB interlayer, This effectively is the surface onto which the image is projected. It also negates the ghosting effect you get on normal glass.


The Weather WILL NOT crack your windscreen.

The cold weather will not crack your windscreen.

That chip you’ve had there for weeks or even months will not ‘turn into a crack’ because it’s cold outside. Fast forward to the summer and the same windscreen repair ‘experts’ will be urging you to ‘get that chip repaired’ because of the hot weather.

We may conclude from this that there is never a good time to have a chipped windscreen. In essence, this is correct however try telling that to the chap who has had a chip on his windscreen for three years (he doesn’t really care too much about the scaremongering because his car has passed its MOT three times since the chip appeared and it’s not in the wiper sweep zone).

Making one small change can potentially help towards preventing your windscreen from cracking.

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Windscreen Defrost Switch Symbol

Once your windscreen has cleared of condensation – or ice – channel the heat away from the windscreen (but keep the cabin warm). It’s not quite as simple, but essentially this is the basis: do not overheat your windscreen.

Thermal expansion.

Direct heat to the inside of the glass will cause the inner layer to expand. While this is going on, the vinyl inter-layer will also soften. Meanwhile, the outer layer (the one with the chip on it) is exposed to a much colder temperature; the heat and movement behind it (plus the torsional forces working through the car’s chassis) could cause the chip to crack. Once the crack extends, it will continue to move until it (eventually) reaches an edge on the windscreen. The same principle works in the summer when you have a much cooler temperature inside the cabin and heat outside the car.

Demist the Windscreen FULLY.

Redirect the blowers AWAY from the windscreen. It’s easy to forget the heater is on and channeling most of the generated heat to the windscreen. In the summer months, leaving the A/C on is great to keep the car cool but be mindful that the windscreen demist/defog is not directing all the cool air directly to the windscreen.

This is not an exact science as there are variables in the type of chip; its position on the windscreen; ambient temperature; temperature changes; the speed of temperature change; terrain (upon which the car is driven) and possibly even style of driving.

Aluminum Windscreens

Aluminum windscreens. Yes, you read that correctly, ‘But aluminum is a metal, and a windscreen is made of glass?’ I hear you ask.

To help make this information easier to process, aluminum glass is actually, technically, transparent aluminum. A sample of transparent aluminum say, a tube, looks like a tube made of glass but it’s actually aluminum. Well, an asterisked aluminum; this is not elemental aluminum but rather a material made from it as the core ingredient.

Transparent Aluminum tube

Despite clearly not being a metal (and not a glass either; glasses are amorphous solids while ceramics are crystalline) transparent ceramics demonstrate impressive properties. Transparent aluminum is produced by a process called sintering. Powdered ingredients are poured into a mould, compacted under tremendous pressure, and cooked at high temperatures over long periods. The resulting translucent material is then ground and polished to transparency ready for use.

Aluminium Oxynitride ( “ALON” ) is a ceramic composed of aluminium, oxygen and nitrogen. .

Aside from being optically transparent (≥80%) in the near-ultraviolet, visible and midwave-infrared regions of the electromagnetic spectrum, ALON is four times harder than fused silica glass; 85% as hard as sapphire, and nearly 15% harder than magnesium aluminate spinel. Since it has a cubic spinel structure, it can be fabricated to produce transparent windows, plates, domes, rods, tubes and other forms using conventional ceramic powder processing techniques. Tests show that a laminated pane of ALON 1.6″ thick can stop a 50 caliber rifle round, something even 3.7″ of traditional “bullet-proof” glass can’t do. ALON also has better optical properties than regular glass in the infrared wavelengths; where most glasses absorb IR, ALON is essentially transparent to it. That makes ALON a great choice for the windows on heat seeking missiles and other IR applications.

ALON also demonstrates superior scratch resistance.

SHUT UP and TAKE MY MONEY!

While the technology exists, there is currently no demand for automotive windscreens. Unbreakable and damage-resistant glass is undoubtedly a game-changer which could spell trouble for many AGRR businesses. However, in applications such as mobile phones, the increased demand for such a material will drive costs down, but windscreens might take a while longer.

An ‘aluminum windscreen’ presently could cost in the region of £30,000-40,000, a price tag which even Monty Brewster might balk at.

Audi A3 Windscreen Replacement

An Audi A3 windscreen replacement. This particular car was an RS3 (in Catalunya Red).

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Audi RS3 Windscreen Replacement

A-pillar covers. I like to take them off. It reduces the risk of damage, and with them out of the way you can check that the bond is making good contact on both the glass as well as the body. There’s a screw at the top of the cover, but before you go yanking on the moulded plastic, you need to free the bottom; and there’s a bit of trim which needs to be separated from the bottom of the A-pillar cover. In order to do this, there is a cover on each side of the dashboard. These must be removed.

The designers have been very helpful by providing a notch towards the bottom of the curved edge which allows you to slip the tip of a trim tool in as you start to ‘pop’ the covers off.

Removing A-Pillar Trim

Removing A-Pillar Trim

The trim can now be removed.

Screw Behind Airbag Cover

There’s a tweeter to disconnect from the cover too:

Tweeter

With the pillar covers removed, the next step is to remove the rear view mirror and the light (and rain) sensor behind it. The sensor is clipped in with a spring-loaded clasp. With the two sides of it released, the sensor will need to be eased out of the mounting bracket very carefully as it will be stuck to the glass with a sticky gel pad. Care must be taken not to go in from the bottom of the sensor as this is where the de-fogging sensor is hiding.

Removal of Rain Sensor

With the interior parts removed, the wipers and wiper cowl can also be removed. There are also two trims – one either side of the windscreen – which must also be removed in order to expose the windscreen edge.

The windscreen can now be released using a cut-out method. Whichever method is used, the emphasis should be on not to damage the paintwork. Here, a cutting wire is being fed into the car via a wire feeder tube. The tube pierces through the adhesive to allow the wire to pass through; a metal guard is positioned so that the act of passing the feeder through does not scratch the paintwork.

Wire Feeder

The windscreen is removed and old adhesive cut back taking care not to damage the paintwork. After cleaning and inspecting the bond line, the surface must be prepared in accordance with the polyurethane adhesive manufacturer’s guidelines.

Once the new windscreen is prepared for bonding, it’s a good time to reattach the rain sensor. A new gel pad is needed for this.

New Gel Pad on Rain Sensor

Steps must be taken not to trap any air anywhere when sandwiching the gel pad between sensor and glass.

Gel Pad Fitted

The new windscreen can now be fitted to the car. I like to date the inside of the glass and provide product details for the adhesive used. The installer’s name and a code for whom it was fitted may prove useful should there be any issues after fitting.

Traceability

Glue on glass or body: opinion is divided. I’m an advocate of applying the adhesive on the glass. You get to discharge the product in one go which means one start/stop point (therefore one join) and the glue gun can be held perpendicular to the glass during extrusion in order to minimise the risk of an effect called tunneling in the glue.

Urethane on Windscreen

The windscreen should be bedded down sufficiently so that when the side trims are refitted, there is no gap between the trim and the glass. If the adhesive is compressed to much gaps can show as the trims are held in on a fixed metal track which does not allow adjustment.

Trims

Audi RS3 windscreen replacement: done.

Comments and questions welcomed.

Dealer Approved Car? Check the Windscreen

Something to consider when buying a dealer-approved, used car.

A returning customer got in touch after he bought an ‘approved’ car from a main dealer. He wanted the non-standard windscreen removed and replaced with a genuine ‘OE’ part. As an engineer, he’s fastidious about most things in his life, especially when it comes to cars; for example his garage wasn’t designed to house his previous car (an Audi S8) so he measured the floor-space and calculated that the car would fit but, it would need to be millimeter perfect if he wanted to a) get of the car after parking it, and b) close the (electric) up-and-over door behind it. In order to achieve this – right first time, every time – he articulated a laser guidance system. It was setup to allow a tolerance of +/- 5mm on one side and 20mm at the front. Aligning witness marks on the driveway, bonnet and door mirrors against the red laser lines as he entered the garage served as checkpoints ensuring he was within tolerances. No tennis-ball-on-a-string for this chap!

Our friend’s keenness to demonstrate how precise his system was sets the tone for why he wanted his new car to be perfect. I watched him approach the garage opening, and the theme for Mission Impossible began to play in my head as he guided the car through an intricacy of omnidirectional lines. The parking was absolute and true to his blueprint. To measure the gap between the nearside door handle and the wall you probably would need a feeler gauge (which no doubt wouldn’t have been far from his digital vernier caliper). Excessive? Perhaps. But his commitment to the cause was wholly admirable. It can also serve as one of the best appraisals of your work when such a customer gives you their approval.

As I noted his latest instructions we discussed the age of the car, “2017” he stated.  The mileage – as ultra low as it was – was irrelevant; this car would still be covered by a manufacturer warranty. With this in mind, I suggested that he speak to the seller about what the outcome would be if there was an issue with the windscreen, or an electronic device connected to it such as the rain sensor or Lane Departure Warning camera. In the event of a (device) malfunction, or issue with the windscreen and/or installation, the manufacturer warranty would not entertain any claim if there is a non-genuine part fitted the workshop will just kick it out, or at least until the ‘fake’ part was replaced with a genuine one.

There was no resistance from the selling dealership as he negotiated the cost of an Original Equipment replacement from them, and a contribution towards having an approved installer fit it. Moving forward, the car now is 100% genuine, with authentic parts throughout, and will now accord with the warranty criteria.

ADAS Recalibration After Windscreen Replacement

Have you had your windscreen replaced recently? Is your car equipped with an Advanced Driver-Assistance System? Were you advised (or even warned) about the need to recalibrate that device? Do you need to look for a windshield calibration repair shop? Whether your ‘smart’ windscreen has been replaced or not, there is a realistic chance that it might need to be in the future, and this is where you could be faced with more questions… or perhaps not. The subject of recalibrating ADAS devices is a Pandora’s Box full of unsubstantiated claims.

For those new to the technology, some background: ADAS systems are designed and developed to automate and enhance vehicle systems for safer and better driving. These features are designed to help with monitoring, warning, braking, and steering tasks. ADAS relies on inputs from multiple data sources, including automotive imaging, LiDAR, RADAR, image processing and computer vision. These devices are mounted in various places in and around the vehicle; some are mounted behind the windscreen. Another great device for your vehicle is Effuel which is a fuel-saving device that helps your car run more efficiently.

ADAS

Advanced Driver-Assistance Systems

Advanced driver-assistance systems are one of the fastest-growing segments in automotive electronics. In terms of car design and evolution, motorists are in safe hands. Ultimately, and until we have autonomous vehicles, the motorist’s hands should however still be on the steering wheel.

Does your camera (or device) need recalibrating after the windscreen has been replaced?

There are a variety of factors to consider, but to cover all bases the blanket response would be to say yes it does. However, before the recalibration apparatus was made available to repair shops, windscreens on cars with ADAS were still being replaced. If the answer is to be yes, why haven’t those vehicles been recalled? The counter argument to that could also be that none of those vehicles needed adjustment, or even, none of them went into default mode after having the windscreen replaced and, worse still, crashed as a result of a misaligned device. There are no reported cases of crashes, injuries or fatalities which were attributed to an uncalibrated camera. Meanwhile, the same cameras are still being re calibrated today.

A motorist emailed me to ask if his device needed calibrating post windscreen replacement. His vehicle featured ‘road sign assist’ which he said he didn’t use anyway. The company who were replacing his windscreen stated that he must drive the car to another one of their sites (30 miles away) to have the camera recalibrated. There was an additional cost implication to this procedure (over £150) as well as his time and fuel to get him there and back. If it was – according the repairer – paramount for his safety why were they sending him on his way, in the compromised car, to another destination 30 miles away? He went ahead and had his windscreen replaced but decided against the recalibration procedure on the basis that he didn’t agree with paying what they were asking for, and then having to embark on a 60-mile round trip in order to get it. Interestingly, he later had his vehicle checked by a manufacturer main agent and there were no flags or faults in the vehicles computer system. Everything worked as it should. The Road Sign Assist device checked out okay.

Traffic Sign Assist

When replacing the windscreen on a vehicle, if the windscreen is a genuine OE product and you are fitting it using the correct bump-stops/trims/damming/mounting components, and within OEM tolerances, as long as you do not disconnect the ADAS device and put the vehicle through an ignition cycle, there is nothing to detect the new part.

Put simply, if you are using manufacturer branded products, fitting them to millimeter precision, and do not put the vehicle through an ignition cycle [with a device disconnected] the car will not know the windscreen has been replaced. It is therefore unlikely that you will encounter any issues. Furthermore, many (if not most) devices are auto-calibrating. They have to be, to allow for constant variables during use. The issues occur mostly (in terms of windscreen replacement) when non-genuine parts are used (referred to as aftermarket parts). Comparing an OE windscreen to an aftermarket copy of it, the differences often become immediately apparent such as misaligned brackets (to which the ADAS device is mounted) or that the material used is inferior. When you mount a camera to its bracket or plate which itself is not positioned correctly, the accuracy of that device is immediately compromised. This therefore, is a scenario where recalibration would be needed. Original parts do not offer any such issues.

The (American-based) Insurance Institute for Highway Safety conducted testing of windscreen-mounted advanced driver assistance systems in 2017 and found that a misaligned camera [on a test vehicle] led to issues with the vehicle’s autobraking and lane-departure warning functions. Honda Collision Marketing Assistant Manager Scott Kaboos summarised after the research that Honda required OEM windscreens be used and that they had seen “many issues” where aftermarket glass led to a situation where the calibration would not “take properly.” After the [repair] shop replaced the windscreen with an OEM edition, “everything worked fine again.” Kaboos stated.

IIHS senior test coordinator Sean O’Malley stated that this demonstrated the need for calibration rather than a ban on aftermarket parts concluding that, “The bottom line is that it could still be calibrated to work as intended.” While a factory-misaligned bracket was found on an aftermarket windscreen, the IIHS found no real issues with aftermarket glass itself, according to O’Malley. Chemical composition, laser refraction and refractive index testing found largely that ‘glass is glass’.

In the UK there have been no reports or stories in the press about firms – nor individuals – being taken to task over negligence. Why? Is it because there have yet not (and thankfully)  been any incidents? Could it also be that there actually isn’t any requirement for an installer to carry out a recalibration? In the same way that any Fred-in-a-shed-with-a-bag-of-tools can replace a windscreen among all the cries of how important structural rigidity is, and how airbags rely on the windscreen to be adequately bonded in order to be effective (provided the occupants are wearing seatbelts in the first instance) anyone can also replace the windscreen on a car equipped with ADAS technology. Is it compulsory to recalibrate those devices? No. Is it necessary to recalibrate them? Maybe.

Whether recalibration is compulsory (after windscreen replacement) or not, are they being checked correctly? Where are the before and after test results? Who is regulating that part of the industry? Who is policing it? How do we know that the procedure was actually carried out? Where is the second printout showing how much adjustment is or was needed? Proof? Is it merely a box-ticking exercise to distance from blame, or something to staple to the invoice to validate the extra charge?

This is a subject that will run for a while, and during that time the ones making the loudest claims in favour of recalibration are also looking for a return on their investment into what is being sold throughout the motor industry as a revenue stream.

Have you had an experience to do with ADAS and windscreen replacement, good, bad or indifferent? Please get in touch.