Bubbles in the pits

[glassdoctor]

Just have a comment to add to the past discussions on this topic. These little bubbles can show up during the cure process. They are not visible prior to curing. Deep drill holes or deep pits are the ones most likely to get the bubble.

There have been a lot of theories in past threads regarding why and what to do to prevent it. Temperature, pit resin viscosity, and cure speed are likely key variabes.

Something I have noticed that I don't recall being mentioned is a big factor. The type of cure film used.

Some months back, I was getting too many of these bubble surprises. The tabs I was using were relativley stiff. I like using them because they last a long time and are easy to work with. The thin film is more delicate and harder to handle and keep track of.

But I went back to a flimsier thinner film to see what would happen. Guess what? No more bubbles. The thin tabs allow the resin to "suck in" while it cures, leaving more of a dimple.

This is what I saw with the resins etc. that I use. Different resins and practices may se different results. I have used stiff tabs without getting bubbles also, and the problem seemed to come and go mysteriously. But in this case, the change in cure tabs was an immediate and striking change.

I would like to hear from others using stiff tabs that never get bubbles, etc and see if there is any pattern here. Maybe Delta has done extensive testing?

[Delta Kits]

Stiff tabs have more of a tendency to have bubbles, but the main culprit is your bottle of pit resin.

We recommend that everyone store their pit resin upside down. When you're ready to use it, don't turn it back upright, but just unscrew the lid, put a drop or two, and put the lid back on.

When you start turning the pit resin upright, then upside down, it aerates the resin and creates bubbles.

[glassdoctor]

I know this is a common tip, and it's certainly at fault in some cases. But I don't think the bubbles I get are from aerated resin at all.

In the past I have done tests such as using a bottle that has been sitting still overnight, and letting the resin and tab sit all day without being cured to see if any bubbles appeared before the cure. No bubbles after sitting for hours, then a magic bubble after a one minute cure. I have also put pit resin in a syringe to try to eliminate the air in the resin, but that didn't do much.

In my case, I did nothing different other than change tabs. I store and handle my resins the same way. That's why I posted the results.

What about resin viscosity? I have used relatively thin pit resin and very thick resin. I don't recall a difference there, but I have not tried to trace any patterns.

[Delta Kits]

GlassDoctor,

My post was general in nature, and not specific to your problem. Most air bubble problems in pit resin are due to aeration.

In your case though, obviously that's not the case.

Do you get curing tabs directly from a windshield repair equipment manufacturer? The reason I ask, is when we were looking around for a material for curing tabs, there are MANY materials that seem like they would work, except that they have a coating on them (which the manufacturer may or may not happen to mention) that has turned resin milky, created air bubbles, etc...in test cases.

So, if you are buying them strictly for this purpose, i'm sure that's not the problem, but if you're making them yourself, i would find a new material.

[glassdoctor]

Interesting, Jeff. I'm curious about the effects you mention, particularly the discoloring resin. I haven't seen this before. Did this happen immediately, or weeks later?

Do you know why a coating or particular material would cause bubbles?

I know I have tried a few materials that didn't work well due to various reasons, like adhesion to the resin.

Some tabs I have used are form wsr suppliers and some are "homemade". The "wsr" tabs I have used have been pretty thick and stiff. I like using thicker tabs better, but they were getting more bubbles. The tabs that work really well for me are 3.3 mil polypropylene sheet protectors. I have used this on and off for years. Another thing I like about this material is that it's the least "sticky" tab I have used. Most tabs will stick to the resin if you remove it before the resin is cured well. These tabs can be pulled off "mid-cure" without sticking. This is useful for larger pits that need a second "fill"... you can peel off the tab and add another drop early in the cure process.

[Coitster]

I used the curing tabs for years and then when I developed my new technique that allows me to not have to scrap over the resin hole and yet its completely flush with the glass and clear as a bell. I now only using the curing tape. Delta sells them for a few bucks and they are well worth it. I have heard of people using packaging from cigerates and also syran wrap, you got to be kidding me. Some people just take the cheap thing to a new level. Hope I didn't offend anyone but don't go cheap on your supplies.
David
Coitster

[GRT]

Its weird but I've been having the bubble problem again. It seems to come and go. Like no problems for a few months, then bam, there BACK.. Its got me scratching my head because I use the same good quality supplies I've always used. Keep the pit filler upside down ect....
It sure makes me mad when I have to dig bubbles out of a pit with a needle.

[Delta Kits]

I'm curious about the effects you mention, particularly the discoloring resin. I haven't seen this before. Did this happen immediately, or weeks later?

Immediately noticeable. We had a pile of different manufacturers and materials, and just tossed all the ones that had any sort of effect on the resin.

[glassdoctor]

Coitster, I gotta go get some seran wrap now!

Actually I have seen a demo video that showed the guy using what looked like seran wrap... the really flimsy stuff, like a sandwich baggie. Hmmm, sandwich bags.... be right back.

What is the difference between curing tape and tabs? Is the tape the really flimsy stuff? I remember you talking about that pit fill technique, and it would have to be really thin stuff, huh?

[Coitster]

When I end a chip repair and I am filling the pit left over, I use the pit resin. Its specialy desined for that. I only use thin resin to fill the chip itself.
David
Coitster