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Screen Saver

Got a cracked or chipped laminated windscreen? Here's the cost-effective way to fix it...

By Michael Knowling

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Windscreens - you never give them a second thought do you? Not until they get damaged that is. And according to research, the average driver will experience some form of 'screen damage every seven years. So what do you do when it comes your time - fork out for a new screen, or just let it get worse and deal with it later?

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Neither! Windscreens O'Brien have a hi-tech laminated windscreen repair technique that's an extremely cost effective alternative. And it also complies with the Australian Standards for Windscreen Repairs (AS/NZS 2366) - of course.

That certification is no small thing either, because the integrity of your windscreen is imperative in the event of a major accident. As the Windscreens O'Brien's literature tells us, "a damaged windscreen is a potentially weak and dangerous windscreen". And that's not good. As much as one-third of a vehicle's upper body strength actually comes from the front and rear glass. Furthermore, most modern vehicle's passenger airbags rely on the windscreen remaining in position for maximum effectiveness. So retaining the whole of the windscreen's original strength is obviously of utmost importance.

On completely another level - but, undoubtedly, one that most people take more notice of - windscreen chips and cracks also interfere with windscreen wipers, create light distortion, impair vision and are potentially dangerous distractions. Unfortunately, it's only natural to have your eye drawn towards a chip in a windscreen when you should really be watching the road. And another recipe for trouble comes about because the damaged part of the windscreen inherently bends the light rays coming in. This sends false information to your eyeballs, which can trick you into thinking that that approaching semi-trailer is a long way off - when, in reality, it's bearing down perilously close. Ouch.

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The most common cause of windscreen damage is - not surprisingly - from stones thrown up by other moving vehicles. Especially on unsealed roads. The best thing you can do to avoid damage to your windscreen is to hang a reasonable distance back from the vehicle in front (bearing in mind stones can flick up a long way), and pass cars coming from the opposite direction at a sedate speed.

But - dammit! - imagine that, no fault of your own, one day you've just copped a nasty "bullseye" chip in your windscreen through. Some box-head driving in front wandered off onto the gravel shoulder of a bitumen road and kicked up a shower of stones - right onto your windscreen. What do you do now?

Well, here's the process...

1. Take Action - Fast!

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Immediate windscreen "first aid" prevents cracks from spreading further through the glass, eliminates dirt and water contamination and also improves your chances of a virtually invisible repair. So as soon as your windscreen is damaged, it's important to act. Windscreens O'Brien has available (free) clear stick-on saver patches, which should be placed over the damaged area as soon as the damage occurs. These are the ideal cover, but - if need-be - a clear piece of sticky tape will suffice. Just keep it clean and sealed off. Next up, you'll have to get the damage repaired ASAP. If not, the damage can worsen (due to things like chassis flex and changes in temperature) and you might end up with cracks growing right across the glass. Repairs can be done by either dropping into the nearest Windscreens O'Brien branch, or by ringing for a call-out repair.

2. Squaring Up the Job

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The first step is to assess the windscreen's damage against the Australian Standard for Windscreen Repairs (AN/NZS 2366). This Standard was set following extensive research, testing and industry consultation. It identifies a Critical Vision Area (CVA) and places limits on such things as the size and location of the damage. The CVA is essentially the section of the windscreen that the driver is most frequently looking through. The Standard dictates that this area extends 15cm left and right from the centre of the steering wheel, begins 90mm down from the top of the windscreen and finishes 65mm from the bottom edge.

Here's a table specifying the aforementioned size limits for repairs on various types of damage in areas both inside and outside the CVA:

  Inside CVA Outside CVA
















As above for each type of damage in the combination

As above for each type of damage in the combination

In addition to the limits mentioned above, the Standard says repairs should not be done if:

  • There are already two or more repairs in the CVA and the new damage is also within this area.
  • There are eight or more previous repairs anywhere on the windscreen.
  • Any crack starts or finishes at the edge of the windscreen.
  • The damage affects more than the outer layer of glass (a laminated windscreen has inner and outer glass layers and a vinyl interlayer).
  • The damage has deteriorated the windscreen laminate bonding layer.
  • There is a previously repaired crack over 100mm in length.
  • Damage is in the CVA and there is an adjacent previous repair within the overlay area (150mm x 50mm).

Failing any of these means that the windscreen cannot be repaired and - although it is not law - windscreen replacement is recommended as soon as possible.

3. The Repair Technique

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After being deemed appropriate for repairs, your autoglazier will bring out his or her big case of goodies - a full Glass Medic Kit. They'll dive into it and - if the damaged area is full of compacted glass - pull out a probe and a fine brush to remove it. However, our photo-example 15mm diameter bullseye hit is already perfectly clean since Windscreens O'Brien inflicted the damage with a small lead ball there and then before our very eyes - all in the name of good PR!

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Note that during most of the job, a stick-on mirror is placed on the inside of the glass to make viewing easier.

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Where required, a small drill is used to make a fine hole into the centre of the damage area - usually the position where the glass has been struck. What this does is provide a feed for the polymer resin to flow through - which occurs later in the process.

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A plastic vacuum cup (with a sealing compound run around its foam rim) is then placed over the damaged area. This is plumbed into a 12V powered pump that provides a small amount of vacuum inside the wound. Five minutes is the standard duration for this step.

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The next step involves injecting an optically matched polymer resin into the drilled hole (which is still under vacuum). An applicator is used to drop around 5-10ml into the top of the vacuum cup and a "flat probe piston" is then screwed down on top of it. The piston's action past a certain point inside the cup reverses the pump cycle so that it now delivers positive pressure - thus aiding the flow of resin into the glass.

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It takes ten minutes for the polymer to get into all of the "fingers" of the damage zone. During this stage, you can even watch the polymer flowing through the minute cracks and crevices in the glass. Notice that protective gloves are used when handling the polymer resin. This stuff is ultra strong and can strip a car's paint while you watch!

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With the polymer still in a liquid form, the vacuum cup is removed and in its place goes a Mylar patch to keep the resin inside the glass. This has to be done very quickly, because the resin will run back out and down the windscreen if given half a chance.

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Next is the curing stage, which converts the liquid resin into a solid. The 12V socket is raided to power a small UV lamp, which sticks onto the glass over the Mylar patch. The ultra-violet rays cause a reaction in the resin that causes it to harden. Approximately five minutes passes before the polymer resin has fully cured.

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After the resin has set, a razor blade is used to scrape away the disposable Mylar patch and any excess resin about the place (a daub of polish is also placed in the working area to prevent scratching the glass).

And that's about it. The only thing left is to give the glass a nice cleaning over with a clean cloth and some glass cleaner. Thirty-forty minutes and the job's done!

The Result

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Glass repairs are difficult to detect if you don't know they're there - but some tiny evidence is invariably left behind. This appears as a small dark shadow within the glass, and a small strike mark often remains on the surface. Look closely at this photo and you can see the finished repair (as a small mark on the left side of the mirror) alongside another fresh bullseye hit (the big mark on the right). Note, though, that the quality of the repair depends largely on how clean the wounded area is kept once the damage is done. Once dirt gets in it's impossible to suck every last bit out - and that shows up in the end result.

However, marks (if any) are minimal and (more importantly) cracks won't get the chance to spread further across the screen. Further to this, Windscreens O'Brien's Technical Manager claims "repairing the windscreen restores it close to its original strength" - which is obviously good news if you're ever in a big accident.

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Windscreens O'Brien also offers a nationwide, written guarantee on workmanship, materials and repairs for as long as you own your vehicle. Not bad eh?

So get cracking!!! (but not literally)


Windscreens O'Brien Website at

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