Step by Step: Repairing a Chip With a DIY Kit

A DIY chip repair is mostly preparation and patience. The resin work takes ten minutes; getting the conditions, the pit and the seal right is what decides the result. Read the whole procedure before you open the kit, because several steps cannot be undone once resin is in the break.

Confirm the chip is a candidate

Kits work best on a bullseye or small half moon under about an inch, at least 2 inches from the edge, outside the driver's primary viewing area, not penetrating to the inner ply, and less than a week or two old. If you are unsure what you are looking at, use the damage identifier and check it against the repairability rules. A star break with long legs, a combination break or anything touching the edge is a poor DIY candidate and is better handled as described in DIY versus professional.

Set up the conditions

• Shade, not sun. A garage, carport or building shadow. If none is available, wait for early morning or evening, or shade the windshield with a sunshade laid over the outside while you work.
• Glass temperature roughly 60 to 75 F, the band consumer kit resin is blended for. Feel the glass with the back of your hand: it should feel neutral, not warm, not cold. If the car has been sitting in sun, give it 30 minutes in shade to come down. If it is cold, run the cabin heat gently on low for 10 to 15 minutes and then turn it off. Never blast the defroster on high at a chip. The temperature reasoning is spelled out in temperature and repair quality.
• Dry. No rain in the last several hours, and no washing the car that day. Water inside the break has to leave before resin can enter.
• Wind and dust. Avoid a dusty or windy spot. Grit landing in an open pit is contamination you cannot remove later.
• Light. Have a flashlight. You will use it several times.

Prepare the break

1. Do not wash the windshield first. This is the most common opening mistake. Water wicks into the fracture and takes hours to leave.
2. Clear loose glass from the pit. Use the pin or scribe from the kit, or a clean sewing pin, and pick out the crumbs of glass sitting in the crater. Work gently and vertically. Do not lever sideways against the crack legs.
3. Dry the break if there is any doubt. Warm the area gently and evenly from inside the car with low heat, or leave the car in a warm dry garage for an hour. Then let the glass return to working temperature before you continue.
4. Clean the surface around the pit only. Isopropyl alcohol on a lint-free cloth, wiped in a ring around the damage so the seal has clean glass to sit on. Never spray glass cleaner: most contain ammonia, and ammonia and silicone-based protectants both contaminate a break so resin will not bond. Let the alcohol flash off completely.
5. Do not touch the pit with your fingers. Skin oil does the same thing as a protectant.

Mount the applicator

Center matters more than anything else in this step. Look through the mount hole and line it up directly over the pit, not over the middle of the whole break pattern. On an adhesive pedestal you get one attempt, so hold it above the glass and sight it before the adhesive touches. On a bridge kit, place the suction cups, then adjust the feet so the injector barrel points perpendicular to the glass and lands squarely on the pit.

Press the seal down firmly enough to compress the rubber ring evenly all the way around. On a curved area of glass, check that the ring is contacting on all sides rather than bridging on two.

Resin and pressure cycles

1. Add resin. Follow the kit's quantity, usually a few drops into the chamber or a pre-measured syringe. More is not better: excess resin ends up on the glass surface where it will cure and have to be scraped off.
2. Draw the plunger back first if the kit allows it. Hold it for 30 to 60 seconds. This is a weak substitute for a professional vacuum cycle but it does pull some air out of the pit and the near part of the legs.
3. Apply pressure. Push the plunger down, or thread the injector down, to steady moderate pressure. Hold it for 2 to 5 minutes. Do not lean on it. Excess force flexes the glass and can run the break.
4. Release, then reapply. Back off to neutral for 30 to 60 seconds, then apply pressure again. Each release lets trapped air migrate back out through the resin, and each pressure stroke pushes the resin front a little further. Three to six cycles is normal.
5. Flex the glass gently if your kit instructs it. With pressure released, press with two fingers on the inside of the glass directly behind the break, just enough to open the legs a fraction, then let go. Very light pressure only. Over-flexing is one of the fastest ways to run a chip into a crack.
6. Check the fill. Release pressure, look from inside with a flashlight held outside at a low angle. Clear means filled, silver means air. Keep cycling on any silver legs.

Pit resin, curing strip and cure

1. Remove the applicator. Lift it straight off. On an adhesive pedestal, peel slowly from one side. Wipe any resin that ran onto the glass with a dry cloth before it cures.
2. Add pit resin. One drop of the thicker pit resin (or the same resin if the kit has only one) into the surface crater, enough to sit slightly proud.
3. Lay the curing strip. Place one edge down first and roll it flat across the resin so air is pushed out ahead of it. A trapped bubble cures into a permanent dimple. Press gently outward from the center with a fingertip or the flat of the razor.
4. Cure. Move the car into direct sunlight, or use the kit's UV light. Sunlight typically needs 5 to 15 minutes depending on season and angle. A UV light usually needs 2 to 5 minutes at close range. When in doubt, cure longer.

Leveling and cleanup

1. Test the cure. Peel a corner of the strip. If the resin under it is still tacky, lay it back down and cure longer. Scraping soft resin tears it out of the pit.
2. Peel the strip fully in one steady motion.
3. Level with the razor. Hold the blade almost flat against the glass, no more than about 10 degrees, and push it across the cured button in one direction. Several light passes, not one hard one. A steep blade angle gouges the resin out or scratches the glass.
4. Clean up. Now you may use glass cleaner, on the surface only, away from the repair. Check the result from inside and outside, in daylight.

Time budget for each step

Troubleshooting

Expect a faint visible mark when you are done. That is normal even for professional work, and what a repaired chip looks like sets the realistic standard. If the result is poor and the damage is in your sight line, price the alternative with the cost estimator before deciding what to do next.

Frequently asked questions

What temperature should the glass be?

Aim for glass surface temperature around 60 to 75 F, the band consumer kit resin is blended for, which sits inside the 60 to 80 F window shops work in. Below about 50 F resin thickens and will not travel into fine legs. Above about 85 F it thins, runs, and begins curing from ambient ultraviolet light before the break is full. Touch the glass rather than trusting the air temperature.

Can I do this in a parking lot on a sunny day?

Only if you can get the windshield into full shade, such as a garage, a carport or the shadow side of a building. A sunshade over the outside of the glass while you work is a workable substitute. Sunlight hitting wet resin starts the cure immediately.

How do I know when to stop injecting and cure?

Shine a flashlight through the break from the opposite side and look at the fracture planes. Filled fracture is nearly clear because cured resin matches the refractive index of glass. Any leg that still flashes bright silver still holds air, and curing now makes that permanent.

What if resin leaks out around the seal?

The mount is not flat or the glass under the seal is not clean. Remove it, wipe the ring area with isopropyl alcohol, let it dry fully, and remount squarely centered over the pit. On a bridge kit, adjust the feet so the injector is perpendicular to the glass, not tilted.