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A deep crack is not a chip you can repair almost invisibly. It is already a 20–30 cm line or more running from the impact point across the glass. A studio has six months of relative freshness on a 5–8 mm chip; on a deep crack, it has 24–48 hours. Beyond that window, the chances of saving the glass drop every day. Below: what a technician physically does with a deep crack, what "stopping" a crack means, the limits of the method, and when the honest answer is straight to replacement. For owners who have just found a long crack on the glass and are trying to decide whether to rush to the studio or to start ordering new glass.
Contents
- What a "deep crack" is — and how it differs from a chip
- The 48-hour window — why freshness matters
- What the technician does to "stop" a crack
- Limits of the method — when "stopping" no longer works
- Pricing and the repair-vs-replace decision
- What to do right now if a crack starts
- FAQ
What a "deep crack" is — and how it differs from a chip
In auto glass repair industry terms, damage is sorted by several parameters. A chip is local damage up to 2 cm — an impact dot plus short legs or a round cavity ("bullseye"). A deep crack is a line from 5 cm and longer, running from the primary impact point across the glass.
The key difference is direction and growth dynamics. A chip is static — it is either there or not. If no crack has grown out of it in 6 months, odds are it never will. A crack is dynamic. Every temperature swing, every road bump, every wiper press lengthens it by a millimetre or two. A 10 cm crack becomes 25 cm in a month. A 25 cm crack becomes edge-to-edge in another month.
Typical Tbilisi dynamic for a deep crack: day 1 — heater click, 15–20 cm line on the glass. Day 2 — driver runs errands, gravel patch, crack grows to 25 cm. Day 5 — cold night, morning warm-up, crack moves on, now 35 cm. Two weeks in — the glass is no longer repairable in principle, replacement only.
This is why a deep crack needs different logic from a chip. A chip can wait a couple of weeks (though not in winter). A deep crack waits a day or two at most.
The 48-hour window — why freshness matters
The polymer resin used by the technician fills the inner cavity of the crack and bonds its walls. That works under two conditions only: the cavity is clean, and the cavity has not grown so much that the walls no longer meet plane-to-plane. Time breaks both.
First 24 hours. The crack is fresh, almost no contamination inside, walls smooth. Resin penetrates to full depth, UV cures it into solid plastic, walls are bonded together. Cosmetic result: a thin visible line (the crack does not vanish), but structurally the glass is restored. The point is — growth is stopped.
24–48 hours. Dust, condensation moisture, wiper particles start getting in. Resin penetrates worse, the bond is partial. Cosmetic result: the line is more visible, a darker streak may remain where the contamination sits. Structurally the glass holds, but the risk of regrowth is higher.
After 48 hours. The crack has had at least one day of operation to live in. There is dirt inside, salt at the edges (winter) or road dust (summer), the walls may have shifted from vibration. Resin no longer bonds properly, the repair becomes cosmetic without structural value. A few weeks later such a "fix" usually grows again from the same crack tip.
A week or more — almost always replacement. Exceptions exist, but they are rare and each case is judged separately.
What the technician does to "stop" a crack
"Stopping" a crack (industry slang: "crack stop") is not glass restoration but damage localisation. The goal is not to restore appearance, but to fix the crack length so it does not grow further.
The process:
- Inspection and assessment. Technician looks at the crack under a lamp, measures length, evaluates the crack-tip type (sharp, split, branched), checks penetration depth into the laminate. Decision is made — try "stopping" or recommend replacement straight away.
- Drilling the trap point. At the very tip of the crack, exactly where it "wants" to grow next, a tiny ~1 mm hole is drilled. That micro-hole is a physical trap for stress. As a crack grows, it follows the line of maximum stress; a round hole redistributes that stress around its circumference and the line cannot continue.
- Crack cleaning. Isopropyl alcohol and compressed air clear out everything that has gotten into the crack cavity in the last few hours — dust, moisture, reagent residue. The cleaner the cavity, the better the resin bonds to the walls.
- Resin injection along the line. A bridge injector moves along the crack in 2–3 cm steps, filling the cavity with resin and pulling air back at each point. It is slow — 30–40 minutes of injection alone on a 25 cm crack, not counting other stages. No rushing: a missed segment becomes a future growth point.
- UV curing. A clear film is laid over the full length of the crack (pushing out the last air under the resin), then the UV lamp goes on top. 8–12 minutes per segment, the lamp moves stepwise along the length of the crack.
- Trim and final polish. A blade slices off the bead of resin protruding above the surface, a polishing compound finishes it. Result — the crack line stays visible up close, but the glass surface is flat to the touch and wipers ride over it cleanly.
Total time on a 25–30 cm "stop" — about 90 minutes. That is 2–3x longer than a standard chip repair.
Limits of the method — when "stopping" no longer works
Not every crack can be "stopped". There are situations where the technician gives an honest "replacement only" right at inspection.
A crack that has reached the edge of the glass. If the crack line has joined any edge (top, bottom, side, inside the wiper-sweep area), a trap point will not work. The crack is coming from the edge, and the edge cannot be trapped — there is no "next centimetre" where a trap could be set. Glass gets replaced.
A crack in the driver's direct line of sight. A rough 60 cm rectangle in front of the steering wheel. Even a perfectly stopped crack leaves a visible line and 1–2 mm of optical distortion in that zone. By Georgian law any damage in the driver's zone is a formal reason for a failed safety inspection. Cheaper to replace immediately than to drive with the risk of a fine and an inspection.
Multiple crack legs from a single point. If the impact point has thrown 3–4 long lines in different directions, each one needs its own trap. Technically possible, but the cosmetic result after such a "stop" is worse than a new glass and structurally the glass stays weak in the centre. Acceptable on a donor car, usually not for daily driving.
A crack with a glass fragment broken off deeper than the laminate. If a piece of the outer glass layer chipped off at the impact point, or worse, the damage went through the laminate film into the inner layer, injection is useless. Resin has nowhere to go, no bond is possible. Glass gets replaced.
A crack on a car with an ADAS camera in the camera's field of view. Modern cars with assistant systems (lane assist, autopilot, automatic braking) have a camera behind the mirror looking through the windshield repair. Any damage in its field of view throws off system calibration. BMW, Mercedes, Toyota and similar manufacturers only recalibrate after a glass replacement, otherwise the ADAS warranty is void. Repair in that zone is formally possible but legally and operationally not advised.
Pricing and the repair-vs-replace decision
Our pricing for deep crack repair:
- Crack up to 15 cm — from 95 ₾
- Crack 15–30 cm — from 140 ₾
For cracks longer than 30 cm, the final price is set at the in-person inspection — crack shape, location and accessibility all play a role. A long but straight, accessible crack sometimes costs less than a medium but awkwardly shaped one.
Glass replacement:
Replacement is carried out at dedicated glass specialists in Tbilisi; each studio prices differently based on sensor, heating and ADAS configuration — check with them directly. BESTAUTO does not replace glass and does not publish competitor numbers.
Decision logic is simple. If the crack is fresh (under 48 hours) and meets "stopping" conditions — try repair. Cost is many times lower than replacement, the risk is clear (if the repair fails — the labour money stays with the studio, and replacement happens anyway). If the crack is old, in the driver's zone, or has reached the edge — replacement immediately. There is no point paying for a knowingly bad repair, especially if replacement is coming anyway.
Booking glass repair in the first hours after the crack appears makes sense. Final decision — after an in-person look under the lamp, takes 5–10 minutes.
What to do right now if a crack starts
Scenario: you just noticed a 20–30 cm line on the glass that was not there an hour ago. What to do in the first minutes.
Do not panic, do not "rush" to a studio across the city right away. Every road bump, every turn, every burst of heater grows the crack. If you have a choice — first kill the thermal load (heater on minimum or off, no airflow on the glass), then drive calmly to the nearest studio without hard acceleration.
Do not try "home methods" from the internet. Clear nail polish, epoxy glue, duct tape, electrical tape — none of this fixes anything. They either do nothing or they get in the way of a later studio repair (glue and polish create UV-light interference, tape leaves sticky residue). If the glass is going into a studio, take it in clean, no "preservation".
Phone ahead. Knowing a technician with an injector is waiting saves 30–40 minutes. On the call describe length, location and time of appearance — the technician will say right then whether to come in or to start ordering new glass.
Take photos. If you have KASKO insurance, a glass claim usually wants before/after photos from the service. Fresh photos taken before the crack grew further help with the insurance claim.
And one last point: the crack is not "urgent" in the "drop everything, drive immediately" sense. It is urgent in the "do not push it to next week" sense. The gap between a repair today and a repair in 3 days can be the gap between "stopped" and "replacing the glass".
FAQ
Can I drive with a deep crack until the weekend to make it to the studio?
Technically — yes, if the crack is not in the driver's direct line of sight and has not reached the edge. But every day of operation grows it by a few millimetres. If the crack appeared on Tuesday and you only booked Saturday, there is a high chance that by Saturday the "stopping" window is gone and replacement is the only option. Better to carve out 90 minutes the same day.
What does "stopping a crack" mean and why does it stay visible?
"Stopping" means the crack does not grow anymore. The cavity inside is filled with polymer resin that has bonded the walls. Structurally the glass is restored. But visually the line stays — resin has a slightly different refractive index than glass, and part of the crack length may have been "dirty" before reaching the studio. This is not a cosmetic chip repair, it is a structural halt of the damage.
How much does a 25 cm crack repair cost vs a glass replacement?
15–30 cm crack repair from 140 ₾, exact figure set at in-person inspection. Replacement is done at dedicated glass specialists in Tbilisi; each studio prices individually based on sensors, heating and ADAS camera — check with them directly. BESTAUTO does not replace glass. The money gap between repair and replacement easily reaches tens of times. Live repair pricing on windshield repair.
If the crack is already a month old, will repair help?
In most cases — no. A month inside the crack is enough contamination to prevent a proper resin bond. Plus the crack has almost certainly grown — what was 25 cm is probably 35–40 cm now. The technician will still look at the glass under a lamp and give an honest answer, but 9 times out of 10 it will be "replace".
What if the crack appears at night in winter and the studio only opens in the morning?
Main thing — do not run the morning warm-up at full power. Before driving in: open the car, do not turn on the heater, or set it to absolute minimum aimed away from the glass. Keep the glass from taking another thermal shock. Outside in the morning do not pour any water on the glass, do not chip ice with anything metal. Drive to the studio carefully, no hard manoeuvres or potholes. Phone in for 10:00 as soon as the studio opens. Between a night-time crack and a morning visit the gap is 8–10 hours — still inside the 48-hour window, "stopping" odds are good.
Conclusion
A deep crack is damage that needs a decision in hours, not days. The studio has a 24–48 hour window in which resin injection plus a drilled trap point can lock the crack and save the glass from replacement. Beyond that window, both cosmetics and structural reliability drop every day, and a week later the only option is usually a full replacement at a glass specialist instead of a 95–140 ₾ "stop" at our studio.
The method has limits. A crack in the driver's zone, a crack to the glass edge, a branched crack, a crack through the laminate — none of those are repair candidates. An honest technician says so right at inspection, refuses the work for the money's sake, and does not leave you with glass that will need replacing anyway. That criterion — willingness to say "replacement only" right away — separates a working studio from a place that takes any money for any procedure.
Key takeaways:
- A deep crack = a 5+ cm line that grows every day of operation.
- "Stopping" window — 24–48 hours from appearance, then odds drop.
- Method: trap point at the crack tip + resin injection along the full line + UV curing.
- "Stopping" does not restore glass clarity — line stays visible but does not grow.
- Replacement is mandatory: crack in driver's zone, crack to edge, crack through laminate.
- 15–30 cm repair from 140 ₾, replacement at glass specialists (we do not replace). The money gap reaches tens of times.
Book a crack inspection and "stopping" attempt at BESTAUTO via the windshield repair page or by phone to whichever studio is more convenient in Tbilisi, Georgia:
- BESTAUTO Guramishvili — Guramishvili Ave. 78, tel. +995 550 000 299
- BESTAUTO Politkovskaya — Anna Politkovskaya St. 51, tel. +995 550 000 199
Both studios are open Monday to Saturday, 10:00–20:00. Before the procedure — a free under-the-lamp inspection, crack measurement, freshness assessment, and an honest call on stopping odds. If repair is no longer the answer — a straight reply on that and help with ordering the replacement glass.
