chip took off

[bill lambeth]

Has anyone every had a chip run after you reapired it.This was a nickel size bullseye.Very easy repair.The repair come out very good but when I pulled my mirror the chip run about a foot and half.I am sure that it was probably a replacement that was in a bined.Any thoughts?

[GlassStarz]

another reason to pressure cure at the point you started removing stuff it was filled but not cured resulting in it taking off. Even if the pit seems hard doesnt mean the stuff inside is yet the glass filters the uv and it takes longer.
Rule of thumb is when removing injector and mirrors etc be gentle things are not set up.

[Brent Deines]

another reason to pressure cure at the point you started removing stuff it was filled but not cured resulting in it taking off. Even if the pit seems hard doesnt mean the stuff inside is yet the glass filters the uv and it takes longer.
Rule of thumb is when removing injector and mirrors etc be gentle things are not set up.

Sorry GS, but that makes no sense to me what so ever. I've had chips begin to run when applying pressure, but never when removing pressure. I believe that if you cure under pressure you are far more likely to have problems after the repair is cured, especially if the glass is already under stress.

The only way to pressure cure is either from the inside of the glass, or from around the perimeter of the injector, both of which require far more time than placing the light directly over the break. Even with the very best of lights you need at least double the cure time if curing from the perimeter or from the other side of the glass. Of course Bill has not told us if he cured under pressure or not, or even if the break was cured before it ran for that matter.

I think you are probably on the right track Bill. A shield that fragile was likely to be installed improperly, either from the factory or in the after market. Of course we have not explored the glass temperature, the resin temperature, how the mirror was removed, etc. There could be a number of factors that contributed to the running of the break, but I think it's fair to say having a properly filled break run after curing is a rare event regardless of your beliefs about curing under pressure.

[GlassStarz]

I read it to say when he pulled his mirror not when he released pressure it spread Whether pressure cure is used or not (and we all know how you feel about ipressure cure brent)
The resin obviosly wasnt cured if the chip was properly filled it shouldnt have taken off regardless of glass mfg. Thus something happened to make it spread I have watched several people reach in and tug off the mirror which would cause a flex and once in awhile prob a spread. Im sure most experienced techs (and mfgs) are careful when they remove stuff we all learn to be.
I have seen people push down on the injector to get a good suction on the suction cup rather than lifting the edge some times this flex will spread things as well sme mfgs have a suction pump for the cup to eliminate this

Either way if it spread right away one of two things happened IMHO eiter it wasnt filled correctly or the resin wasnt cured

[bill lambeth]

I did not cure under pressure.I swiveled my bridge over and took a peek before I started the curing process.The repair looked good.After thinking through the repair,I think I got in a hurry and was a little rough when I pulled the mirror off.I do cure under pressure in some repairs but not always.I agree with Brent about the pressure cure.I think that if you take your time you will not have to cure under pressure.I always swivel my bridge over and look at the repair before starting the curing process.As you all know,there can be air under your tip that you cannot see,so I always look at it.

[screenman]

Was there any chance of moisture being present, just a small amount at the end of a leg can make it a lot weaker than a dry repair. we show this sometimes in training by getting the guy to flex the end of a leg on a repair he has done and cured, if there is just the slightest amount of moisture left in the leg then it will run quite easily.

[CV Windshield Repair]

Brent, how is it possible to cure a repair from the inside? Doesn't the lamination prevent the uv lamp curing the damage that is on the outside. I once repaired a windshield that was damaged on the inside of the windshield when it was time to cure I removed my towel that I was using to shade the repair from the sun. The repair never cured!

[Brent Deines]

Brent, how is it possible to cure a repair from the inside? Doesn't the lamination prevent the uv lamp curing the damage that is on the outside. I once repaired a windshield that was damaged on the inside of the windshield when it was time to cure I removed my towel that I was using to shade the repair from the sun. The repair never cured!

As to why your repair "never" cured, I really can't say, but the PVB does not block 100% of the UV rays and does not prevent curing. UV rays will penetrate both layers of glass and the PVB layer of a windshield, but curing through the inner layer of glass and the PVB layer does at least double the curing time.

I can't say I have ever tried to use the sun to cure a repair to the inside layer of glass, but depending on the time of day, the time of year, the altitude, and other factors, the sun can be a bit unpredictable as a UV curing source. I don't recall the numbers right off hand, but when you compare the amount of UV produced from the sun on a sunny summer day vs a sunny winter day in the same location, there is a substantial difference. That's not to say the sun is not a powerful UV source, just that it does not produce a constant value like a good UV light will.

Testing with a UV spectrometer is a very simple process that measures the amount of UV light through a windshield, through plastic, out in the sun, or under a light. They are a bit on the expensive side, but very enlightening. There are a lot of false claims floating around about how much UV some lights produce, but the spectrometer ends arguments about such things in a matter of seconds.

[Guelster]

As to why your repair "never" cured, I really can't say, but the PVB does not block 100% of the UV rays and does not prevent curing. UV rays will penetrate both layers of glass and the PVB layer of a windshield, but curing through the inner layer of glass and the PVB layer does at least double the curing time.

I can't say I have ever tried to use the sun to cure a repair to the inside layer of glass, but depending on the time of day, the time of year, the altitude, and other factors, the sun can be a bit unpredictable as a UV curing source. I don't recall the numbers right off hand, but when you compare the amount of UV produced from the sun on a sunny summer day vs a sunny winter day in the same location, there is a substantial difference. That's not to say the sun is not a powerful UV source, just that it does not produce a constant value like a good UV light will.

Testing with a UV spectrometer is a very simple process that measures the amount of UV light through a windshield, through plastic, out in the sun, or under a light. They are a bit on the expensive side, but very enlightening. There are a lot of false claims floating around about how much UV some lights produce, but the spectrometer ends arguments about such things in a matter of seconds.

How about a cheap UV Meter? Would one of these do the trick?
http://www.q3i.com/uvhawk_series.php

[Brent Deines]

Never tried one. Never seen one for that matter. I would think accuracy might be limited, but who knows? Anyone else tried one of these?