Advice On Moisture & Cracks

[paulrsf]

Sometimes when I use the Delta moisture evaporator on a bulls eye to help in removing Rainex or to dry out moisture from the break, a small crack will result, usually no more than an inch or two. When I attempt to complete the repair, I can't seem to get the resin to flow into the crack evenly so I am left with a bulls eye that looks repaired and a small crack extending outward that is less than acceptable.

1. How can I help to avoid causing the windshield to crack when drying out moisture from the damage area?
2. How can I get the resin to flow into the crack if one develops as a result of drying?

Thanks for your input.

Paul

[Glasseye]

1) Avoiding cracking while using evaporator - if cracking is happening on a regular basis you are probably overheating the glass. make sure you use the equipment as recommended by the supplier and allow enough time between heat cycles for the glass to cool down, which will reduce the risk of a break occuring.

2) During the repair process keep checking that any cracks are filling correctly i.e. looking at the crack from different angles to check for the crack becoming invisible. It may take a while, but as long as you can see improvement keep doing the process. It may help to gently flex the glass from the inside or apply a small amount of heat to aid resin flow. As long as you keep the work area covered from uv light you can work and rework the repair. Using something like a bubble dome is useful for this.

Occasionally I have a bullseye to repair with a small crack at the base of the " cone" of the bullseye. To get to that crack I drill down into the cone to ensure the resin will flow into it.

[Mr Bill]

1)apply a small amount of heat to aid resin flow. .

I have found that applied heat to a crack causes the crack to pinch closed and expell any resin which may already be in the crack.
Has anyone else noticed this?

[screenman]

Certainly heat will cause most damages to shut, with luck when it cools this will draw the resin in. Most guys mistake glass expansion with the damage filling, certainly most do not allow sufficient time for the glass to cool down again properly before curing.

[JWG]

heat in cycles...dont get in a hurry.
if a crack occurs, use a crack expander and plenty of TIME.

[screenman]

Why use a crack expander if it is not needed, I find very few cracks need an expander on them. If you have an unstable crack then I would say do not use a crack expander and if you do exercise extreme caution. A lot of cracks that run an inch or two with the Drystar are subsurface and a crack expander would be of no use.

[paulrsf]

The cracks that are occurring occasionally while using the Drystar are particularly difficult for me to fill for some reason. Taking a guess, I think it is because the heat has caused the glass to expand inward around the crack and it is too tight to fill. I've tried waiting awhile to allow for cooling but I am still having problems ultimately getting the resin to flow. When the resin does flow into the crack it often stop before the end and I am left with a pocket of air at the far end. I'm using a UV Dome or a UV shield, so I don't think the resin is prematurely curing making it difficult to flow. Next time something like this happens I am going to take a photo of it so I can show exactly what I am looking at.

Paul

[David T]

Paul,
I have had the same problem. It is gut wrenching to use a moisture evaporator (maximum time; 20 seconds), and hear the sound of a crack starting to run in the first five seconds of application.
Living in an area where there is nearly 100% humidity year round and rains nearly every day during the Summer, I have found it valuable to use the moisture evaporator for almost every repair (I will sometimes skip this step if a car has been kept in garage for several days).
After much discussion with Brent and Korey (and several forum members), this problem was almost totally resolved by using a "hair dryer" to SLOWLY warm up the damaged area BEFORE using the moisture evaporator (a heavy duty 100' extension cord makes this easy).
Sometimes, no matter how carefully (or slowly) the hair dryer is used to warm the damaged area, a crack may develop and start to run. In my experience, these cracks have been VERY small (less than 1/2"), but after taking some time to slow down the warming process (and then using the moisture evaporator after wards), and letting the WS cool before the repair is done, the "new" crack has always filled. This recently happened and the customer could not find the damaged area after completing the repair.
If you do a forum web search, there is a wealth of information on this topic that much more experienced WSR techs have posted.
Hope this info is helpful,
David

[paulrsf]

David-
Thanks for taking the time to reply. Great information! I suspected the small cracks that develop when using the Drystar had to do with the variance between the WS and the quick rise in temp. I notice the cracks are less frequent when I use the Drystar in a circular motion in the area of the damage before actually applying 20 seconds directly over the break. Like you, I need to use the Drystar very often, mainly to melt Rainex or some other wax treatment before using some steel wool to remove it from the damage area. Also like you, each time I use it I get a small pit in my stomach hoping that no cracks develop. I am going to try your recommendation of using a blow dryer to heat the glass so that the difference is not so extreme when applying the moisture evaporator. Also, it makes sense to let the glass cool for a longer period (something I am guilty of not doing -I'm a little impatient). I have seen a lot of posts on which dryer to use.
--Has anyone found an acceptable portable blow dryer that will work with the Delta Kits 12V battery pack? That would be more convenient for me than carrying a long extension cord for an AC outlet. Also, not every repair is indoor where there is power.
Thanks again for the reply.
Paul

[Brent Deines]

Paul, we do not recommend using a 12V hair dryer with the Delta Kits battery pack. It works great for lights and moisture evaporators, but is not meant to power a hair dryer or heater. Also, the ones I have used do not work nearly as well as an inexpensive AC hair dryer. There was a post not long ago that gave info on a couple of 12V models that technicians have had good luck with, but I think we bought both and still found them to be inferior to most AC models. In any case, if you use a 12V hair dryer please use a larger power source than the Delta Kits battery pack.

However, I do agree with using a hair dryer and certainly recommend slowly warming the glass around the break, or better yet the entire windshield if that is practical, prior to using the moisture evaporator. We do that and have only had one break start to run in the past few years, and I believe that was because one of my technicians did not warm the glass prior to drying out the break with the moisture evaporator. That doesn't mean it can't happen, but in my experience it's the rapid temperature change that causes the problem.