COMMON REPAIR PROBLEMS
Take a break – with water
Water in and on a windshield can come from direct impact (rain, snow, car wash, etc.) and from condensation where the temperature of the glass drops below the dew point of the moist air surrounding it. This causes the glass to fog. Whatever the source, water in and on a glass repair site can ruin your repair for two reasons, one mechanical and one chemical. For a repair resin to bond to a glass surface, the resin and the glass must be in total contact. If a film of water keeps the glass and the resin apart there will be no bond. Since the surface of a glass break is as full of hills and hollows as a mountain range, it is easy for a film of water to be trapped in that rough surface.
A chemical problem comes from the fact that most glass repair resins contain one or more chemicals that absorb water from the air or from the surface on the glass. Absorption may dilute the resin and lower its strength or even prevent the resin from curing at all. (This is why resin used on a windshield should never be returned to the bottle where it may poison the whole container, and why it should be capped when it is not being used to load an injector.)
So how to get rid of water? There are no foolproof methods, but there are a couple of tricks that sometimes work, and both are based on speeding up the rate of evaporation of the water in the repair site.
If the surface of the glass is covered with water, put off the repair because there is little chance water can be removed, but if the surface is dry, sometimes an injection of Dry Out Solution may help clean out any water lurking in the site.
Inject a few drops of Dry Out Solution into the break. Cycling the injector (vacuum – pressure back and forth) will help mix the solution with the water.
Next, leave the injector in the vacuum mode for a minute to drain out much of the mixture. Applying heat to the break will evaporate the rest.
A small hair dryer is a good source. Do not use an industrial heat gun as it will damage plastics and possibly melt the inner layer. Keep the gun moving to minimize hot spots, heat the entire length of the repair just to the point that the glass becomes uncomfortable to the touch. Then let the glass cool to room temperature before injecting the resin since some resins will boil and vaporize at temperatures the hair dryer can produce.
Given the wide variation in the composition of the windshield plastic interlayer and the fact that plastic and glass both age unpredictable, be very cautious with both alcohol and heat. This is particularly true if you are working near any aftermarket glass treatment that might not like either alcohol or heat and do not forget that even a drop of alcohol may ruin an expensive paint job.
HOW TO FILL STAR BREAKS
There are three basic ways to coax resin out to the tips of the legs of stars. The first is vacuum pressure. The second is through the application of heat to the inside of the windshield, and the third is by using the flex method.
- Almost everybody is familiar in one way or another with the vacuum pressure method. It consists mainly of creating a seal between the injector and the windshield, and then through various processes creating vacuum to remove air while applying pressure on the resin to take the place of the existing air. When the stars' legs refuse to fill completely, the process is repeated one or more times.
Pros: Simple with most systems. Very little chance of starts' legs spreading.
Cons: Very time consuming and has very little success on damages larger than a nickel or a quarter.
- The application of heat to the inside of the windshield is another process that many of you are familiar with and often use in conjunction with the vacuum pressure method. Some technicians advocate using heat during the vacuum segment and some advocate using it during the pressure segment. Let's examine what happens in a leg during the introduction of heat so you can decide which to use and when.
As soon as you apply heat to a start damaged windshield, two things begin to happen:
A. The viscosity of the resin begins to drop making it thinner so it flows more easily.
B. As the temperature of the glass increases, the glass begins to expand and the leg of the crack begins to close leaving less space between the walls of the crack.
Now, if you apply heat during the vacuum segment of the process, theoretically the expanding glass could close the crack and force air out. However, the danger here is that when the glass expands too much, it closes to the point that the refraction disappears, leading the technician to the assumption that it has resin in it, and he begins the curing process only to find that when it is cured and the glass cools, there are few tips that have refraction and are not bonded, and the star reappears.
Now, if we apply heat during the pressure segment, the glass warms, heating the resins and causing it to flow more easily, helping the technician repair the damaged area more quickly. However, if you are to get positive results from the process, you must give great attention to the temperature of the windshield as you are adding heat.
Too much heat will again cause the leg to close down, giving it the appearance of being full without any resin in the tips. Also, at temperatures slightly over 115 degrees, you can begin to damage the qualities of your resins.
Pros: On cool windshields the average stars can be repaired more quickly with little effort IF close attention is paid to the temperature applied to the glass. This takes practice and close concentration!
Cons: Often legs close due to expanding glass leading to premature curing and incomplete fills. Also, the process is nearly useless on warm and hot windshields. If there is a drastic temperature change you can cause the cracks to grow if heated locally. And finally, the process has only limited success on stars larger than a quarter.
- Some of you may not be familiar with the flexing method, but give me your attention and we will examine this one closely. Before beginning any repair, it would be wise to make sure the windshield is at the best temperature. If it is too hot, cool it down; it it is too cold, warm it up. Next, make sure your injector and resins are at room temperature. This helps ease many complications before they arise.
With everything at standard temperature and pressure (STP), prepare your tools, resins, windshield, damage, etc., as usual. When you affix your tools (holding structure) to the windshield, be careful to have enough bridge pressure to create a seal with the o-ring and no more. Excess pressure only increases the chance of damage spreading and reduces the effectiveness of the flexing method. After you have completed your initial standard vacuum-pressure, allow the resin to flow on its own for several minutes.
If, after several minutes, some of the legs have not filled, try flexing them one at a time. Apply a little pressure directly onto the leg in question as close to the injector as is reasonable.
First, start with very light pressure and watch what happens to the unfilled portion of the crack as you gradually apply more pressure. What happens is the crack begins to open up at the base of the crack next to the laminate. Each crack will require a slightly different amount of pressure. As you apply pressure it will seem that the crack spreads towards the injector. As the crack opens, areas that are full will begin to lose contact with resin. This is evidence the crack is opening. As soon as you see it opening, hold the pressure constant. At first hold it for about twenty seconds and watch the resin flow out to the tip. With most cracks one exercise will be enough.
Water, Water Everywhere
Whatever the source, water in and on a glass repair site can ruin your repair for two reasons - one mechanical and one chemical.
For a repair resin to bond to a glass surface, the resin and the glass must be in total contact. If a film of water keeps the glass and the resin apart there will be no bond. Since the surface of a glass break is as full of hills and hollows as a mountain range, it is easy for a film of water to be trapped in that tough surface.
A chemical problem comes from the fact that most glass repair resins contain one or more chemicals that absorb water from the air or from the surface of the glass. Absorption may dilute the resin and lower its strength or even prevent the resin from curing at all. (This is why resin used on a windshield should never be returned to the bottle where it may poison the whole container, and why it should be capped when it is not being used to load an injector.)
So how to get rid of water? There are no foolproof methods, but there are a couple of tricks that sometimes work, and both are based on speeding up the rate of evaporation of the water on the repair site.
High and Dry
If the surface of the glass is covered with water, put off the repair because there is little chance water can be removed. If the surface is dry, sometimes an injection of alcohol may help clean out any water lurking in the site.
Use isopropyl (rubbing ) alcohol but remember alcohol has a lower boiling point than water, so it evaporates faster. When mixed with water, the mixture will have a lower boiling point than water alone, so the mixture will evaporate more quickly than water does by itself.
First, check with your injector manufacturer to see if the injector assembly will be damaged by alcohol. If not, inject a small amount of alcohol (just a few drops) into the entire length of the break.
Keep in mind that a film of alcohol is as bad as a film of water and that the entire alcohol and water mixture must be removed from the repair site before any resin is introduced
With or without alcohol, heat removes water since it speeds evaporation. A small hairdryer is a good source. Do not use an industrial heat gun as it will damage plastics.
Keep the gun moving to minimize hot spots. Heat the entire length of the repair just to the point that the glass becomes uncomfortable to the touch. Since some resins will boil and vaporize at temperatures the hair dryer can produce, let the glass cool to room temperature before injecting the resin.
Given the wide variation in the composition of the windshield plastic interlayer and the fact that plastic and glass both age unpredictably, be very cautious with both alcohol and heat. This is particularly true if you are working near any aftermarket glass treatment that might not like alcohol or heat. Do not forget that even a drop of alcohol may ruin an expensive paint job.
One Leg will Not Completely Fill
The unfilled leg is either not connected to the pit or may be too narrow in the "gap" between the pit and where you can see the leg.
First, with your pump on pressure cycle, use your probe to push down on the unfilled leg, holding it open until the resin flows in. If this fails, remove the pump and use your probe to push down on the glass between the pit and the unfilled leg. This will crack the glass and open a path for the resin. If this also fails, insert a number 14 sewing machine needle in the pit at an angle toward the unfilled leg and tap it lightly to open a passage. A drill can also be used.
Resin Cannot be Pumped into the Break
The cylinder of your repair bridge may be screwed down too tightly on the glass. This could close up the legs of the break. It only has to be tight enough to prevent the resin from escaping.
There is No Access for the Resin
Drill the impact point and "pop a bullseye" to join the legs. There was probably a previous attempt at a repair that blocked access. Some drivers are under the impression that they can prevent a break from spreading with nail polish or Super Glue® products.
Other causes could be the use of a windshield repair kit sold by auto supply stores or a bungled attempt by another technician. In most instances nothing can be done about this, though drilling and popping a bullseye may work. Remember that if it looks bad or cracks out, your reputation suffers.
Getting Out of the Fog
A common problem in doing repairs is a "foggy" appearance when the repair is complete. If the proper steps are not taken, this will usually lead to a dissatisfied customer.. The "foggy" appearance is generally caused by moisture mixing with the resin in the break, but can also be the result of some other factors.
Moisture in the Break Moisture in the break can be the result of a few different things. The most common causes are rain, sleet or snow. If the vehicle was washed recently you may also see moisture in the break. If moisture is present, you will need to remove it before starting the repair process. There are some effective moisture removal tools available. The application of heat from a cigarette lighter can also be used, but caution is necessary because of the risk of running the break.
In some instances, the moisture may not be present in the break before you begin work on the job. It is possible to contaminate the break with moisture by using a syringe that may have had moisture in it from a previous cleaning or from washing the glass prior to making the repair. If this happens you should look for the "foggy" appearance while performing the repair. If you notice it prior to curing the resin, it can be removed by going through a vacuum cycle to remove the contaminated resin. Then clean the area, dry the break and repeat the repair process using a clean and dry syringe. Never inject unused resin into the original bottle once it has been removed because it could contaminate all of the resin in the bottle. Only draw the proper amount from the bottle when doing a repair.
Other causes of Discoloration Solar coated glass – The coating on these windshields is applied to the inside surface of the outer piece of glass. Once air reaches this coating it will become discolored.
Lamination separation – This will sometimes be found in breaks that are old and have been exposed to the elements for some time. The moisture may have been removed from the break, but because the plastic has been in contact with the moisture it will start to discolor.
In both these instances the discoloration will most likely be present before starting the repair.