Crack Out Liability ? and Introduction!

[Brent Deines]

With the air temperature around 60 degrees how did the windshield get so hot? It is about 60 degrees out here in Eugene right now and my car has been parked in the full sun for several hours. The glass temp is about 75 degrees.

Like Bill, I often lay my hand on the glass and if it is too hot to keep it there comfortably I cool the glass down, but if I can hold my hand on it I proceed with the repair. Not too scientific but it works well for me.

Was your resin significantly colder or hotter than the glass? In my experience it is putting cold on hot or hot on cold that increases the chance of crack outs, not just repairing hot glass. In fact, I prefer to work on glass in the 80 to 100 degree range, and my repair time drops in the summer as it takes me less time to cool the glass than it does to warm it to my preferred working temperature. Sudden temperature changes of any kind make me nervous however, so I never spray anything on the glass. If you do choose to spray something on the glass to cool it, be sure the liquid it not too much colder than the glass and cover the chip before you spray it. Generally I just shade the glass and open the windows of the car and by the time I get ready to inject the resin the glass is at a reasonable working temperature, but if the ambient temperature is 100+ degrees and the glass has been in the full sun for awhile it does take a bit longer. We used to get some of that in Montana, and of course in Arizona and Texas they get it all the time, but we don't have that problem much in Oregon.

Bill brought up another good point about some cracks being invisible on hot days. It's not always a case of the glass cracking when you start injecting your resin, but sometimes just that the crack is opening up so you can see it. Never the less, it's not a good feeling and not something your customer is going to understand. Yes it is part of the business, but it should not happen very often if you are managing your temperature and pressure properly.

[Dave M]

Ricersux,
As stated here before, the heat sync tool is not used to cool down a windshield that may be too hot for a repair. It is used after moisture has been evaporated from a break and the break area, where the heat was applied is too hot. You put the heat sync on the glass, over the break, to cool it off prior to putting the injector in position. It only cools the area covered by the tool!
I have used the heat sync many times here in Maine with great results. It does as advertised. Since we're talking about temperature changes on the glass, I have a question regarding the heat sync. I've always been a bit leery putting the cold aluminum tool directly on the hot "spot" fearing that a drastic temp. change would further crack the break. So much so that I touch the glass in 1-2 second burst before actually setting it on the break. Your thoughts Brent!?

[t4k]

I had the heat sync expand the legs on a chip about two weeks ago. You definitely want to use it with care on a hot W/S.

[Ricersux]

Brent, I checked the temp of the glass after it cracked out and it was 107f and my resin was around 55f, I guess that could be a factor too. I simply didn't take the correct precautions before starting the repair imho. I had a leg jump out about 3 inches this winter by apply too much heat too soon but I was able to terminate the leg and I was able to get it filled and was quite happy with the results. I learn something everyday that helps with my technique and the quality of my repairs.

[Brent Deines]

One of my first and one of only a few crack outs that I have had was due to the exact same thing. Windshield well over 100 degrees and resin about 60. As soon as I started injecting the resin the crack took off and it happened so fast I could not get the bridge off in time to make any difference. I also had the same thing happen when a windshield was very cold and I used room temp resin. Since I started matching resin temp to glass I have had very few problems with crack outs and I really don't get all that concerned about glass temperature other than I try to warm or cool a large section of glass rather than a small area.

I'm still trying to figure out how the glass got so hot with an ambient temp of only 60. Did you heat the glass or was it that hot just from the sun?

[screenman]

In my early days of testing with the heat sink tool I took the glass temperature way above what we would normally do, and then applied the heat sink, not once did I have a problem. Just looking at hot glass is enough to break it let alone man handling it by sticking bridges and screwing down injectors, cooler glass is far more robust. This is why I keep my heat in as small as area as possible when drying out, if it does run it will stop sooner on cool glass. As someone else said if it is to hot to put your hand on it is too hot to work on. When checking temperatures with your hand use the fleshy part under your thumb, this is a very tender area and will give you better feel than any other part.

[Ricersux]

I did not heat the glass it was sitting in direct sun light at around 1pm. In the winter I use a small hair dryer to warm the glass prior to using the drystar and it works great...takes a few minutes longer but everything works better at the 60 to 80 degree mark.

I just need to get into summer mode and cool the glass to the correct temp and I think all is good.

Brent, what do you recommend for cooling down windshields? This is my first year being mobile only, its much easier to control these factors with a brick and mortar but much too expensive.

[Brent Deines]

Well let me say right off that this is one of those areas where I do things a bit differently than many other technicians. I generally just shade the glass. In this area that is generally enough.

In warmer climates I have worked in I would run the defrosters with the air conditioning on cold whenever possible in addition to shading the glass. A lot of people think this method cracks out windshields, but I have yet to have that happen. If the air conditioning in the car has not been running I will turn the temp to as cold as possible and use the defrosters. The air will begin blowing hot air and then slowly cool down so the glass is also cooled slowly, but evenly and efficiently.

If I can't move the car I will use a pop up tent or lay a beach towel across the entire windshield to shade the glass before I start, and if possible open all the windows to help cool down the inside of the car.

I have also used a wet beach towel to cover the entire windshield, covering all of the chips with chip savers first of course. I find that works better than spraying a liquid as the glass temperature of the windshield is dropped, not just the spot you are working on, and the towel seems to absorb the heat better so you don't have to keep re-applying the spray. You can spray the entire windshield but it will begin to heat up again immediately after the liquid evaporates. Keep in mind I use warm water to soak the towel, not cold, so as not to shock the glass, which I have found to cause crack outs.

It's interesting how many techs on this forum say that hot glass is more apt to crack out than cold glass. I have not found that to be true at all in my experience. In fact, in Montana where the temperatures can get well over 100 at times in the summer and below zero in the winter, the vast majority of crack outs occurred in the winter, and in out training classes we have found that if we heat the training room up several hour prior to creating the damage and starting the class we are less apt to have crack outs than if leave the heat off in the training room until it is time to make the damage and start the class.

Regardless of whether the glass is hot or cold, in my opinion the most important thing is to match your resin temp to your glass temp as closely as possible. I know I have said this many times in the past, but I think it is worth repeating as I believe it is one of the most important factors to consider to minimize crack outs, and it is often overlooked by windshield repair technicians.

I also have to say that in my experience warming and cooling the entire windshield is far preferable to spot warming or cooling, except when it comes to super heating for the purpose of removing moisture. In that case I recommend heating the entire windshield, or at the very least a spot several inches larger than the damage to a working temperature that is on the high end of your normal range prior to using the moisture evaporator. In my case that is around 100 degrees. That way when the moisture evaporator is applied the shock to the glass is minimized. I then use the Heat X-Changer to to cool that spot quickly, but again, the Heat X-Changer does not need to be, and should not be, cold when you put it on a hot windshield. If it is 20 degrees cooler the Heat X-Changer will work well, but if it is 50 degrees colder it could shock the glass to cause a crack out.

It’s hard for me to hear that crack outs are such a big problem with some technicians as I have had very few. Whether you take my advice or the advice of other technicians that have different theories based on their experiences, just be sure you are taking advice from someone who does not have a high percentage of crack outs.

[kennycrane]

I cracked out my first ws the other day, wow I could not believe it. it was a beautiful day 75 degrees a car had been setting out in the sun all day. I had been use to warming ws so never gave it any thought. I dried any moisture out with my moisture evaporator cooled it off with my heat exchanger. when i got on the break and applied pressure no thumb pressure 2 min. into the pressure cycle I was looking at it to see how it was filling and CRACK 6'' to the side and 6' all the way to the top of the ws. I was sick, but it had to be that the windshield was very hot and I am sure that my resin was only 75 degrees at the most. Costly and humbling but I feel I know what caused it so I can prevent it next time. Thanks for all of the great tips on this forum!
Idabel, Okla.

[newman]

crack outs very rare (have had none doing well over 2000 repairs) ins jobs covered.... cash jobs tell customer not savable or pay up !?!?!