moisture evaporator episode

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David T
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moisture evaporator episode

Post by David T »

Greetings all,

As a habit (here in the deep south where it rains daily during the Summer), I have used Delta's moisture evaporator on every repair.

Today, I did 2 repairs on one windshield. One was a small star break and the other was a much smaller star break with a single "leg". I used the moisture evaporator on the larger of the 2 for the recommended 20 seconds. Then, I applied the evaporator to the smaller star break and within 10 seconds, I heard a very low volume "cracking" sound, while watching (in horror) the single "leg" in the break extend by an additional 3/4" of an inch.

The vehicle was in the shade, the windshield was NOT hot (well under 90F). After 5 "pressure/vacuum" cycles and a small amount of heat applied to the inside of the windshield, the crack totally filled. In fact, after taking the bridge off the windshield and putting it back in the tool box, it was difficult to even find where the damage originated in order to apply pit resin.

My question is: has anybody had a crack extend when using a moisture evaporator? Because my area has nearly 100% humidity and rains almost every day during the Summer, I have found this tool to be almost essential in eliminating small amounts of moisture/water trapped in a "star break" or a "bulls-eye" before doing a repair.

However, if using it can cause a crack to "run", I'm feeling somewhat reluctant to continue using it on every single repair. If anybody can offer any feedback or suggestions, it would be greatly appreciated.

Thanks,
David
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Roo
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Re: moisture evaporator episode

Post by Roo »

I had the exact same thing happen to me yesterday. However it was a large combination break(slightly bigger than a quarter) with 3 small legs coming from break. I judge my dry out based on recent weather and yesterday we had lots of rain in Denver so I decided to dry it out to be safe. Well at about 15 seconds in to the dry out one of the legs ran about 2 inches! After 5 pressure and vac cycles and adding a little heat to inside I was able to fill the entire crack without drilling. This makes me nervous to use the drystar although I did dry out 3 mores without increasing the damage. I will be watching this thread closely to see what everyone thinks.
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Re: moisture evaporator episode

Post by screenman »

Just make the amount of time you apply the drystar for slighty shorter, I have certainly had it happen when I first started using one, however with practise that now happens less. Drying out is an absolute must in most weather conditions if the screen is even had the slightest chance of being damp in the last 24 hours then there is a chance of moisture being present.

The nice thing about a crack out from the drystar is that the break will normally stop running when it hits a cooler area of glass, which is why when I use a blow torch I also only heat a very small area.
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Brent Deines
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Re: moisture evaporator episode

Post by Brent Deines »

David,

You specifically said the windshield was "not" hot before you started, but you did not say what the temperature was. Whenever you are applying extreme heat, such as with a moisture evaporator, to a small area, it is always best to warm the glass around the break first. We recommend 80-100 degrees but I like it to be closer to the 100 degree mark before I use the moisture evaporator. That said, I have yet to experience a crack you, but anytime you are heating the glass quickly there is always a slight possibility of that happening.

In your case I can't help but wonder if the 3/4" crack was already there but filled with water so you could not see it. The crackling sound could have been the water as it began to boil, especially if there were chemicals in it from a car wash, washer fluid, etc. I have experienced that. Although possible, in Roo's case I think that is unlikely as 2 inches is a lot of crack not to notice. However, while trying to film a long crack repair recently, the crack was so tight that without pressure from the inside of the glass you could not see the last 4 inches or so, but as soon as you flexed the glass from the inside it opened up. When pressure was removed the crack disappeared again. Although heat expands the glass and tends to close cracks, heat can create enough movement in the glass to open a very tight crack, especially if it has moisture in it. We did not save the video because the crack was just too hard to film, but looking back on it I wish we would have saved it to show just how invisible an existing crack can be at times.

I have heard some technicians on the windshield repair forum say they have a high percentage of crack outs when using the moisture evaporator, but considering the number of times I have used it with no crack outs I have to believe they are doing something incorrectly. I would not necessarily call what happened to you guys crack outs as you were able to complete a satisfactory repair. In fact, if I am correct about David's repair, it may be that it actually identified the existing crack that may otherwise have been missed. Still, even considering these episodes as crack outs, what is the percentage of crack outs you are experiencing? If it is 10% or even 5% that is far too high in my opinion. If it is less than 1 percent I think the benefit is worth the risk, although even 1% would make me nervous, but given the number of technicians we talk to every day that use the moisture evaporator the number of crack outs reported is barely worth mentioning.

I always feel bad for the new technician that breaks out a windshield. Whether due to heat or something else, if your first windshield repair cracks out you have a 100% failure rate and it is very difficult to gain confidence after that. It was years and well over 1000 repairs before my first crack out, which had nothing to do with a moisture evaporator, so although it did shake me up a bit I could rationalize it as being somewhat insignificant in the scheme of things. If it happened today my stomach would still do flip flops, but knowing that my failure rate is so low you can't even put a number to it allows me to continue with confidence whereas the confidence of someone new to the industry may take a very long time to recover.

Just food for thought.
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adam@gtglass
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Re: moisture evaporator episode

Post by adam@gtglass »

And, as a resident of SW Colorado, I know that he is understating the amount of rain that Denver got... Wow, what a storm. My girlfriend's parents were staying with us here in Durango for the weekend, but they live in Denver area; and we watched the news coverage of that storm. Flash flooding is probably a better description.

To stay on topic though, I agree that it could have been hidden by the wetness, considering how wet it was that day. If it was a crack-out, it is surprising that it only went another 3/4 of an inch or so. I could be wrong, but it seems most temperature related crack-outs run out a little further than that if they run at all--at least, in my humble experiences.

Cheers,

Adam
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David T
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Re: moisture evaporator episode

Post by David T »

Thanks for all the feedback. To update, the windshield I was working on was parked in the shade and I would estimate that the temperature of the glass was in the mid 80's (not overly warm to the touch).

While I could be wrong, I don't think there was a unseen crack that was present before using the moisture evaporator. I have previously worked with glass before starting WSR and the sound of it cracking is pretty distinct.

The small crack that developed while using the moisture evaporator could easily have been caused from not using it properly. In the training class I attended (Clearwater, FL), we were instructed to slowly move the evaporator around the damaged area for 20 seconds. In the training class I attended in OR, we were instructed to hold the evaporator over the damaged area and NOT move it at all (which is the method I have been using for previous repairs). Now, I'll make it a point to move the evaporator over the damaged area and keep a very careful watch over cracks to avoid running.

Since 100% humidity is the norm year here (with a daily rain during the summer), I think this tool is essential in making quality repairs. The recommendation Brent made (i.e. applying the evaporator to a windshield that has a temp of 80F-100F) makes sense. If repairs should be made in a temperature range of 70F-90F and the evaporator is used on a windshield that is 100F, isn't there a much higher risk of the resin developing a "flower" like appearance? Other than parking a vehicle in the shade, any suggestions about cooling a windshield down to 90F?

Thanks,
David
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Re: moisture evaporator episode

Post by t4k »

David T wrote:



Since 100% humidity is the norm year here (with a daily rain during the summer),

Thanks,
David

Where are you located....in a rain forest?
David T
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Re: moisture evaporator episode

Post by David T »

t4k,

Where are you located....in a rain forest?

Close, southern Louisiana.

David T
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Re: moisture evaporator episode

Post by t4k »

David T wrote:t4k,

Where are you located....in a rain forest?

Close, southern Louisiana.

David T
Well that explains the humidity and the temperature. :D
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Brent Deines
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Re: moisture evaporator episode

Post by Brent Deines »

David,

Actually holding the moisture evaporator directly on the glass and "not" moving it for 20 seconds is the correct application for drying out a break. I'm sorry if you received incorrect and/or confusing information at the training class in Florida. When using the moisture evaporator to warm the glass you move it around in circles around the break, but not for drying out the break. A number of technicians on the windshield repair forum disagree with our recommendation and recommend everything from less time to moving in circles, to holding the tool away from the glass, but in our testing all of these things make it less effective, which is probably why many of these technicians also have to apply heat with the tool more than once to get the break dry. More than one application should be very rare if used according to the instructions we provide with the tool. That said, moisture will not remain in a break for very long when temperatures are over 100 degrees, and a full 20 second application may not be necessary if the glass is already very hot. The 20 second recommendation assumes that the break is full of water and the glass temperature is around 80 degrees or less. I still use a 20 second application whenever I use the moisture evaporator, but admittedly that is sometimes overkill so although I have yet to have a crack out when drying out a break, you could certainly adjust your time down a bit when the glass is hot if that makes you more comfortable.

I agree with Adam that temperature related crack outs generally don't stop at 3/4", especially if you actually heard the glass crack, but you were there and we weren't, so there is no way for us to know one way or another. Just because we have not experienced it does not mean it is not possible. When working with broken glass we need to expect the unexpected.

I have never had the moisture evaporator cause flowering, but when resin is injected into glass that is over 100 degrees the risk of flowering is certainly higher, so Delta Kits recommends cooling the glass if above that temperature, and always allowing the glass to cool following the moisture removal process. Shading the glass and using the vehicle's air conditioner with the defroster fan on high are how I typically reduce the temperature of the glass. As screenman has mentioned using an aluminum block is also a very effective and safe way of reducing the glass temperature at the area to be repaired, although if the glass around the break is not cooled the break area will not stay cool very long. We have been doing a lot of testing with different aluminum configurations and now have a design that is quite efficient. We'll provide more information about that soon. Other technicians sometimes use water, alcohol, or other solutions to cool the glass. I don't recommend these procedures, but if you choose to use them just be sure you cover the break to keep moisture out, only apply warm liquids, not cold. Soaking a towel in warm water works better than spraying the glass as the towel absorbs much of the heat and shades the glass at the same time, but again, the only time I would recommend using a liquid is if other options like using the air conditioner and shading the glass are not possible.
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