Crack repair tool question

[T-DUDE]

Hey Screenman! I hope this doesn't sound way dumb but are you using a Q-tip or a cotton ball?

Also, are you saturating the Q-tip/cotton ball with resin or are you just pushing the resin that has leaked out to the surface of the windshield along and back into the crack? Thanks!

[puka pau]

Screenman's right: sliding a bridge CAN cause the glass to flex and draw in air, and obviously using a cotton swab is a less invasive technique, and the pressure of the injector seal on the glass CAN pinch the crack and restrict resin insertion but why should any of those objections prohibit anyone from using either or both techniques just because something negative CAN happen? If, for example. I'm confronted with a star break with a leg that won't fill I can use any or all of three basic techniques. I could use a probe to open the leg. Could the use of a probe cause the leg to travel? Yes. I could use heat on the inside of the glass. Could the use of heat cause the leg to travel? Yes. Or, because I use a traditional-style screw-type injector/plunger I could exert some pressure on the injector cap to flex the glass. Could this cause the leg to travel? Of course. So does that mean that I shouldn't use any of these techniques? To my mind not using a technique because something MIGHT happen is kind of a flimsy excuse. I would think that we should all be proficient in as many techniques as possible.
A few things that CAN happen using the surface application technique: A sharp curve or a jagged, zig-zag section in a long crack will accept resin more easily if injected under pressure from a bridge. And it's real easy to trap air in a crack using a cotton swab. If you do flex the glass with a bridge enough to allow air to penetrate into the crack, it's easy to just back up a couple of inches and do that section over - which is something you can't do using a cotton swab.
The successful implementation of any technique is dependent on the suitability of the tools and the expertise of the technician. I use the sliding bridge and the surface application techniques interchangeably, although I use a syringe rather than a cotton swab - it requires way less resin. Actually, I used both techniques on one crack last weekend.
The video demonstrates the efficacy of the sliding bridge technique. I've been using it for over twenty years on literally thousands of long cracks ( I define a long crack as one longer than six or so inches). It's a consistent, reliable and repeatable method. However, you need a bridge with a suction cup (not a vacuum cup). And you need an injector gasket that seals easily to the glass without using excessive pressure. And you need sufficient practice. The upside is that the sliding bridge technique is generally a lot faster than surface application particularily for cracks longer than twelve or so inches and uses way less resin. The only part that's "messy" is the lubricant, but you'll notice in the video that it took the demonstrator all of ten or so seconds to remove the lube from the glass. Anyone who can potentially apply multiple strategies to address a given problem will generally be more proficient and less frustrated. As the late Steve Jobs once said, "Beware of dogma".

Cheers;

Puka Pau

[screenman]

I completely agree with having the skills to do things in different ways, also we should find what works for us. I tend to stop at cracks of about 18 inches now and sell, sell sell, on preventive maintenance as opposed to waiting until the crack has got that long.

[Auto Glass Rescue]

Thanks for all the input, this is great information!

Screenman,
So you are using a cotton swab and not a Q-tip?

Puka pau,
Can you tell me more about the syringe you use, like what type it is and where did you get it?

Thanks,
Eric

[screenman]

Just a Q Tip, If you use a syringe make sure it is UV proof when you lay it back in the tool box. I put only enough resin on the Q Tip to do the job, if it runs down the glass then I have put way to much on it. Just one tiny drop from the dropper will go a long way in filling a crack. Been there and got the T Shirt with a syringe and did not like it.

[Brent Deines]

Done properly it should only take a few drops of resin to fill an 18" crack regardless of whether you slide or surface apply with a dropper, syringe or cotton swab (Q-Tip is a brand name of cotton swabs). Don't be fooled by the length of the crack or the fact that a little resin may drip down the glass, most cracks are actually pretty tight and it does not take much resin to fill them.

[puka pau]

Auto Glass Rescue;

I get my syringes from a retail medical supply store - the kind that sells wheelchairs, crutches, bedpans, etc. There are various sizes available. I buy them in a box of 100.

The trick to using a syringe is to load a cc or two, depress the plunger until you see a drop at the tip and then touch the tip to the crack. Make sure that the beveled part of the needle tip is oriented downward facing the crack and that the needle is held at about a twenty degree+/- angle and that the needle point is in the tiny groove at the top of crack itself. You can find the groove by moving the needle back and forth. Once the tip is seated in the groove apply an extremely light bit of pressure to the plunger - just enough to get the resin flowing. This is the part that takes practice. Its sooo easy to use excessive pressure which of course makes the resin squirt out of the needle and makes a mess.That's the downside. The upside is that when you get the hang of it the resin flowing into the crack through capillary action will just about pull itself out of the needle without using hardly any pressure on the plunger at all and if you keep the needle tip in the crack you can move smartly from beginning to end in way less time and use less resin than you would with a cotton swab or a Q-tip. Done properly, almost no excess resin will be left on top of the crack and no drips or dribbles will be apparent. Obviously, anyone afflicted with an essential tremor, St Vitus Dance or the palsy should probably source an alternative technique. It takes a steady hand.

Cheers;

Puka Pau

[screenman]

I like to have a slightly wet surface to the crack when filling as this helps seal the curing film that I place on the crack as each section fills, this helps prevent any air being drawn back into the crack as you move along it.

[puka pau]

After filling I "wet" the surface of the crack with a thin bead of pitfiller resin before I tab it. The pitfiller mixes with the repair resin to provide a more robust surface seal (particularily with a wider crack) than repair resin alone.

[Vikingfann]

No matter which way you fill the main crack, how do you get a good fill on the original rock chip with spikes that caused the long crack? The situation is typically when the chip is located closer to an edge that the crack has run to. My injector won't hold much pressure or vacuum when the main (much wider) crack runs through this type of chip.

Jere

Attack-A-Crack Windshield Repair
Lake Elsinore, SoCal