Windshield Repair Forum

Since the original topic slid off to another topic I'd like to re-address the original.

The daisy effect on a bullseye is ALMOST always due to TOO much pressure BEFORE the curing and not pressure DURING THE CURING.

(The last statement is arguable depending on the expansion value of resin under pressure as it cures. A value of which I am unaware or ignorant. I think I solved that by making a practice of releasing a very slight bit of pressure before pressure-curing a bullseye but not a star or combo.)

Particularly on a super heated windshield, it is vitally important NOT to apply excessive pressure when injecting the resin into the bullseye break or you WILL crinkle the laminate resulting in the daisy effect depending on the depth of the bullseye.

I SLOWLY screw down on the stem and watch the flow carefully and wait.

If resin hasn't flowed GENTLY with minimum pressure to the entire circumferance of the bullseye, I then CAREFULLY apply a bit more pressure until it does.

When I am satisfied, I pull a suction cycle and then repeat the procedure as many times as necessary to achieve the final result.

And then,

yes and then,

I pressure cure.

That's my story and I'm sticking to it.

But, thanks for your input glassdoctor and Repair1.

I won't mess up this one, since I was the one responsible for the last debacle....

The daisy effect on a bullseye is ALMOST always due to TOO much pressure BEFORE the curing and not pressure DURING THE CURING.

This is about comments my comments, but I think they may be misunderstood, at least partially. I'll try one more time, then I'll ride off into the sunset. I'm not attacking anyone or anything here, btw.

The effect I was referring to is specificly related to the 1-2 minutes when the break is exposed to uv and cures, and not to any daisy that occurs prior to the cure. My point is that given the exact same conditions of pressure and temperature, etc, the break's daisy will not increase in the same 1-2 minutes if not cured. So, my point is that pressure has nothing to do with it, because that same pressure without UV does not produce the same results.

Let's say I do a repair and pressure cure it for 3 min., the pit fill, etc... and it has a slight daisy when done, it looks good. But if you could turn back the clock and just leave it alone for those 3 min., then remove and cure, etc... there may be less noticable daisy lines.

I hope this isn't misunderstood anymore. Every time I try to explain it, I get the same response as quoted about too much pressure, etc.

NOTE: This whole daisy thing I am sure can be greatly diminished by reducing the pressure or working on cold glass. And I understand that others get different results than I do. This is just my observations and nothing more. That's my story... 8)

Try something for me though... after working a combo for 10 minutes or whatever until it's ready to cure, pay close attention to exactly what the outside "lines" look like when you begin the cure under pressure and compare it to the post-cure appearance a couple minutes later. I am curious if anyone else finds there is a clear difference in the degree of the daisy lines, for lack of better english.

hi, ho Silver! And away!!! [-(

If it ain't broke; don't fix it.

Stick with your procedure, glassdoctor. Sounds like it works for you.

We have a particular problem here with REALLY superheated windshields during the summer.

I'm not sure about the expansion properties of resin and would be interested in finding out more.

Assuming a bullseye is properly filled sans daisy, then cured under the pressure cycle, is it not possible that a daisy is then generated by expansion of the resin into the laminate since it has no other direction to go?

(One reason why I very SLIGHTLY back off on the pressure before curing a bullseye and not a star.)

I've found that the most important consideration when dealing with a bullseye on a hot windshield is to very slowly introduce the resin into the CLEANED pit while allowing gravity flow to spread the resin out as much as possible. Carefully increase the pressure until the circumference is filled.

Multiple suction and pressure cycles using gentle pressure cycles will then result in a bullseye that's hard to find.

Yeah, we stick to what works. I definitely don't mean to imply that those who pressure cure with good results need to change. Maybe I can learn from what is doen that works wel for you. We all use different equip. and techniques, and we find what gets us the best results. There are subtle things we all probably do that we can't type out here and we may not even realize... we just do it.

I know I found it hard when I first tried to teach a friend wsr because I had really never "thought" about exactly what I did during a repair... I just did it. I was self taught and worked alone for years. So I had to stop and think about WHY I do what I do etc, so I could better teach my "student".

Multiple suction and pressure cycles using gentle pressure cycles will then result in a bullseye that's hard to find.

Definitely some truth to that. ..

Working bullseyes on hot glass is never good. Resin viscositiy will have some bearing on the results, etc., but room/ambient temps or below will give the best results in general.

I never work on anything on a hot windshield, esp. bullseyes if I want it to really turn out great. Cooling a windshield only takes a couple minutes if you can open the doors. Maybe 5-10 minutes on a 95* day and the car is locked. This is using water, rags and some sort of shade device. I used to work hot glass back in the day, but no more for me.

Reducing the pressure certainly sounds like it would reduce any "excess" daisy effect. I haven't done any real testing of this... and I wouldn't be a good candidate test it, as I don't normally pressure cure.

Actually today I did pressure cure one for a specific reason. It was a star-combo and the center was crushed pretty bad, and there was some stubborn spots right below the injector... and they neede some more cooking to clear up, but the legs and the rest of the break was all done, so I let it cure under pressure for a while to give the small problem area under the injector a chance to either clear up or be cured "clear".

And sometimes I will pressure cure just because I feel like it.

Assuming a bullseye is properly filled sans daisy, then cured under the pressure cycle, is it not possible that a daisy is then generated by expansion of the resin into the laminate since it has no other direction to go?

Well, I think that is very likely... it would make sense. Something has to account for the difference, unless it's all a figment of my imagination. That could be... #-o

But then when you cure pit resin it shrinks. So does the resin expand or does it shrink? I have heard both, but it can't be both now can it? Hmmm... :-k

I think the resin must expand since the cure itself is exothermic resulting in some amount of heat and gas as a consequence.

To what degree the resin expands is still unfamiliar to me and will be related to a host of variables.

Perhaps Jeff could set aside the blue pencil for a moment and enlighten us.

If there was a small half moon and it was covered by the tip of the injector how would one cure under pressure? Most of my curing is done out doors. :-k Thanks

Yes, if the break is small and the injector covers most of it, the pressure cure won't do much. It can only cure what you can see. I know someone will say... "but the glass is clear... the UV will get under the injector..."

Well, it's possible, but it's just my opinion... what's under the unjector doesn't cure, for all practical purposes. Maybe if you let it sit for half an hour?

The guys that pressure cure all the time may have a different view... and they should know better than me...

I

I have heard a lot of comments here about being careful not to use too much pressure when doing a repair, can anyone tell me how much PSI they consider to be safe when performing a repair?

When I did some training at GT my trainer took the pressure up to 60 PSI many times and said it would do no harm. But let me say this same trainer trained me to pressure cure from inside the windshield so I am thinking there are a lot of things I may need to relearn.

I bought a Delta bridge and injector and the instructions say it goes from 5 PSI to I think 15 PSI, Which seems a bit low to me but if one were to somehow measure the PSI when applying thumb pressure to the plunger I think you would get a lot higher PSI.

Anyway I am just looking for comments.

2hipp4u

if it fills the break then ya had enough pressure