Questions on how Crack Eraser resins cure

Tim Evans Uncategorized

Darwin from Portland asks me about the resins being soft and sticky when he cured them. It is a great question and here is his question and my answer to him.

I recently purchased your DIY windshield repair kit and I have some questions related to my first time use since I am running into some difficulties.
My first project consists of a star and a long 18″ crack on my daughter’s car.  I have watched the instruction DVD as well as some of your YouTube videos.  My plan is to attack the star first and apply what I learn form that experience to the repair of the long crack.  To begin I drilled the star and tapped it to get a bullseye.  Then, working with the injector and the “20” resin I was able, with some difficulty, to fill the legs of the star with resin.  Next I set my 8W UV lamp over the star and left it for about 10 minutes.  (This time of year we get a lot of rain and overcast days here in Portland so I’m working inside in the garage.)  After this I observed that the “20” resin was still very liquid.  From what I can see this seems to be the case in your videos too.  I wiped off the excess resin and then applied the CUS resin to the dimple and covered it with a cure tab and again put the UV lamp on it, for about 30 minutes this time.  The CUS resin seemed to set up a bit, but when I used the razor blade to trim and scrape the result it all just seemed to come off, leaving the dimple in the glass exposed.
That experience leads me to ask a few questions:
Does the “20” resin cure and solidify like the CUS resin?
What is the normal curing time for the two resins?
Is the curing time longer at lower temperatures?
Here’s another question after rewatching the videos: At the end of the repair process, or during, when you say to remove the tool, do you mean to unscrew the piston, or the injector itself?
Once I get the hang of this I’m wondering how the finished repair handles window treatments.  Specifically, is it OK to apply Rain-X to the windshield?

Hello Darwin,

All the resins cure to a soft plastic, This is because they need to be flexible because the windshield expands and contracts with temperature changes. So softer is stronger design of Acrylics used in windshield repair. Also they cure sticky unless the air is taken off such as inside the glass or under a cure tab. If you want to check the 20 resin put a drop on the windshield and then put a cure tab on top of it then cure it for 2 minutes and you will see how it cures with the air taken off.

Curing time depends on the UV source you are using. Our lamps cure 20 resin in less than 2 minutes and C resin is less than 1. Temperature is not a big factor in curing.

As for you last question we remove the tool by releasing the suction cup or cups and leave the injector in the tool for the next use.

There are more training videos on the web site here:

and we have a blog where we discuss training tips on a weekly basis here:

Once repairs are done Rain-X will not affect it. If Rain-X is used before the repair it will effect the bonding of the repair resin such as when you said the C resin did not stick to the pit-impact point on the star you repaired, If Rain-X is present the C or Pit filler resin will not stick in the impact area.