Tactics for Controlling Glass Temperature

Mobile windshield repair technicians are often not afforded the luxury of having a climate controlled work environment in which they can perform their services, so controlling glass temperature is an ongoing concern. While there is no perfect outdoor solution, there are several procedures that may be used to safely keep the temperature of a windshield within the optimal temperature range of 70 to 100 degrees Fahrenheit during the repair process.

Warming a Windshield for Repair

If the ambient air temperature is 50°F the windshield could be that same temperature. The glass could also be more than 10 degrees colder if it is in the shade and/or if the ambient temperature had been lower earlier in the day. Conversely, it could be over 20 degrees warmer if the if the vehicle is parked in direct sunlight. Check the temperature with a digital thermometer before you warm it up and then do one or more of the following:

Start the car and turn the defroster fan and temperature control to high.

Some technicians get nervous about this, but assuming the vehicle is not already warmed up, in which case the glass would already be reasonably warm, the defroster will begin blowing cool air and gradually warm up as the vehicle’s engine warms up.  This is a great way to warm the inside of the glass and keep it warm throughout the repair process.

As the glass gets warm you can use the heat and fan control to maintain the optimum temperature.

Using the defrosters will warm the entire windshield which is safer than spot heating.

Warm the outside of the glass with a hair dryer.

Be sure to warm the area around the break so you don’t have any hot or cold spots. This will also help to maintain the temperature if you turn off the hair dryer.

A suction cup mounted hook and a strip of Velcro can be used to hang the hairdryer on the glass so the warm air is directed over the break throughout the repair process. This is particularly important if you are unable to use the vehicle’s defrosters.

A bubble dome may also be used to help trap heat from the hairdryer on the outside of the glass.

Heat using a butane lighter.

As a last resort, or if only a little heat is needed, a butane cigarette lighter may be used to warm the glass from the inside. While quick and handy, heating with a cigarette lighter will leave soot on the inside of the glass, so be sure clean the inside of the glass.

Heating the glass from both sides is preferable but not always possible. If you cannot heat from both sides, or if you only need a little heat, heat from the outside whenever possible.

The primary reason for heating from the outside is that far less heat is needed for the same result. If heating from the inside only you have to heat two layers of glass plus the PVB, so to get the outside lite of glass warm the inside needs to be very hot.

Too much heat can cause cracks to partially close making it difficult to get resin into tight cracks and may cause delamination, commonly referred to as flowering. Delamination is when the PVB laminate begins to separate from the glass. The three main causes for flowering are too much heat, too much pressure, and the age of the glass. Delamination is a structural problem and flowering can be very unsightly.

Cooling a Windshield for Repair

Open the cabin windows to let out the hot air. This is the easiest measure to take and should be the first action to take when trying to cool a windshield for repair.

When a vehicle is parked in the hot summer sun, the glass temperature can be 150° Fahrenheit or higher. While it may be tempting to spray cold water or use a cold wet towel to cool the windshield, the sudden change in temperature may cause damage to spread.

Delta Kits does not recommend cooling a windshield with water because of the risk of cracking the glass, but there are technicians that use this method. If it is used, be sure to cover the damage with a chip saver prior to wetting the glass, and make sure the water or towel is warm, not cool or cold. Failure to head this recommendation may cause the glass temperature to change too rapidly, resulting in a cracked windshield. (Note: A Bubble Dome can also be used to keep the repair area dry. See it in action here!) One or more of the following tactics can also be used to cool a windshield:

Pull the vehicle into the shade if possible.

If it’s not possible to pull the vehicle into the shade, place a hood protector or thick towel over the glass. Keep the glass covered throughout the repair process.

Start the vehicle and run the air conditioning on high through the defroster vents.

The air conditioning will blow warm air at first and then gradually get cooler. The best possible way to cool glass is s l o w l y.

Adjust the air conditioning output to keep the glass within the recommended temperature range throughout the repair process.

A great tip: Be sure your resin is approximately the same temperature as the glass. You don’t want 60 degree resin touching 100 degree damaged glass or vice versa. The injector should also be approximately the same temperature as the resin and glass so it does not cool or heat the resin outside the optimum range.

It is not necessary to have the glass, injector, and resin all exactly the same temperature. Just be sure that they are all within about 20 degrees of each other.

Use minimal pressure when injecting resin into hot glass. Although Delta Kits’ low pressure injector design makes it much more forgiving than other injectors, caution must still be exercised when applying pressure, especially in hot weather.

You may find that you prefer glass temperatures slightly above or below the range recommended by Delta Kits. It is a recommendation, not a law, so as long as you are getting excellent repairs there is nothing wrong with finding your own preferred range. If you start having problems with your repairs however, go back to Delta Kits recommendations and see if that helps.

Note:  Different manufacturers have different recommendations for optimal glass temperature, so if you are not using a Delta Kits professional windshield repair system please consult your equipment manufacturer’s instructions.