Large pit failing

[tooldini]

I have a customer that has a very large pit and it keeps coming out on her. I have done it twice and it came out again. She is very nice about it and I asked her is she minded that I use her car as a test for large pit fills She is cool with it so called again and said it fell out again 3rd time. This thing is about 1/4" or more. I have tried several different pit resins and same thing. Seems someone had a idea a while back but a search turned up nothing. Seems it may have been screenman but not sure. Any ideas would be helpful cause I am going back tomorrow or sunday to try again LOL

[SGT]

Jeff,

Was this pit smooth or rough? If it was smooth, may I suggest using your drill to gently scuff the pit area to help provide a better bonding surface.

If it was rough or even smooth are you sure there was not a hydro phobic coating used?

[Mr Bill]

Last time I was at the dentist I asked to look at his drill and drill bits. He had a drill bit which cut a little ridge inside the tooth cavity so the filling would get a better grip.
Maybe if you drilled sideways at a 45 degree angle into the sides of the pit you could creat some anchorage.

[tooldini]

Thanks guys I will try roughing the edges up, thats kinda what I was thinking but wasn't sure what anyone else thought. It seemed as though it was kinda rough to begin with but maybe it will work to rough up the very outer edges. SGT I don't remember her using rain x or anything but I will ask her again to make sure. thanks again

Jeff

[GlassStarz]

Also pit filler is thicker and doesnt get into all the surface after roughing it p you might try a small amount of thinner resin on the surface and top it with the pit?

[jayjacque]

Are you talking about one of those large chip outs? If so, I discovered it's pretty important to use a good brand of thick pit resin. I had a few come out from a cheaper brand before.

If it's pretty large (after scribing) you might try filling it only part way up instead of all the way, place the curing tab over and cure. Scrape. Then do it again, this time fill all the way, put the cure tab over and cure again.

[tooldini]

I did it today and scribbed the whole pit which was every bit of 1/4 around. I dripped some thinner resin in, then kinda dabbed at it with lint free towel. Then ran my thicker delta pit resin in it. I also cleaned the pit very good and dabbed with alcohol swab to really make sure it was clean before I put filler in. Looked alright when done but we will see in time,, she's gonna call if it fails again. Then maybe I can find some other way or maybe it is just impossible to keep large pits intack. thanks for the help

Jeff

[Brent Deines]

Jeff, it is definitely "not" impossible, and in fact should not require all the extra effort you have put into it. If large pits falling out were a frequent occurrence we would have a lot of very unhappy customers, and plate glass repairs would not even be possible. Fortunately that is not the case.

The "only" time I have experienced this problem is when a hydrophobic coating, or certain types of waxes have been applied to the glass. Sometimes car washes now include Rain-X or wax in their rinse cycle, and now Rain-X has their own windshield washer fluid that also contains that product. In both of these scenarios the % of Rain-X is minimal and diluted with water so it is not much of a problem, but it's still good to be aware of that application since your customers may not even be aware of it.

Most of the advice you have received here on the windshield repair forum so far is spot on, and although I do not recommend using alcohol in the pit area, the procedure you used on this one should provide a good surface for the resin to bond to. In the future I recommend that you make sure there are no hydrophobic coatings on the glass surrounding the pit area as well because when roughing up the surface with a scribe or drill I find that many technicians shy away from the outside edge which can cause adhesion problems.

I recommend that you do one of two things before starting every repair.

1) Test for hydrophobic coatings by covering the chip with a chip saver or piece of tape, then spray water or glass cleaner directly on the area to be repaired. You should be able to tell right away if a coating or wax has been applied if you know what to look for. If you don't know what to look for you should do some testing on treated and untreated glass so you know how each one reacts when water is sprayed on it. Try various different coatings as each one is a bit different. If determined that a hydrophobic coating is present, treat accordingly.

2) Probably a better solution is to treat every break as if a hydrophobic coating has been applied. If you do this you should never have a problem with the pit falling out again.

There are a number of different ways to remove hydrophobic coatings from glass, but one of the simplest, safest, and in my opinion most effective, is to buff the area around the pit with 0000 steel wool, then use your probe or drill to rough up the surface of the pit. The entire process takes about 2 minutes and ends any concern that the pit might fall out. White Scotch Bright pads will work, but in our testing take slightly longer than 0000 steel wool.

Cerium Oxide is very effective at removing Rain-X, but to get the best results should be mixed with warm water, so it takes a bit longer and is a bit messier. I have used Cerium Oxide for years with excellent results, but have recently switched to using the moisture evaporator or steel wool.

Many people don't realize it, but the Dry Star moisture evaporator can also be used to remove hydrophobic coatings, however in order for it to be effective the tool needs to be preheated until the element is red and held flat against the glass for a full 20 seconds directly over the pit area. This works quite well for me as this is how I use the tool anyway, but as has been noted by several windshield repair technicians on this forum, not everyone is comfortable using the moisture evaporator in this fashion. Extreme heat is quite effective at removing hydrophobic coatings so heat guns and torches can also be used for this purpose, but I do not recommend that practice as it is difficult to control the temperature and it is possible to damage the windshield if extreme caution is not exercised.

There are a number of acid based products that will remove hydrophobic coatings, including water spot removers, toilet/shower cleaners, etc., but they should be used with caution as the concentration of acid is high enough that it can be harmful to the skin and in some cases the glass if not removed immediately after application. Although some windshield repair technicians will also inject a break with an acid based chemical, I do not recommend this process due to the possibility of contaminating the resin and/or damaging the laminate, and have not found it necessary.

If you want to test the pit resin, buff a small area on a piece of glass or windshield with 0000 steel wool to make sure there are no applied coatings that could inhibit the bonding process. Apply a drop of pit resin to the surface, cover with a curing tab, cure, remove the tab, and scrape flat with the razor blade at a 90 degree angle to the glass. If the resin pulls off with the curing tab or flakes off in chunks when scraped, you may have a problem with the resin. Since you mentioned that you are using a Delta Kits product I find that a very remote possibility, but testing the resin will help narrow down the possible causes of your problem. If the resin adheres to the smooth glass surface and scrapes off consistently, the problem is not in the resin and since the rough surface of the pit area is a better surface to bond to than smooth glass, there is no reason for the pit to "ever" fall out.

One last thing I should add. On most repairs I still test the area for hydrophobic coatings prior to beginning the repair, and if I determine that the glass has not had a coating applied I don't do any of the above procedures and have no problems with the pit falling out of even the largest repairs. That's not to say that preventative measures are not a good idea, but just that they should not be necessary on the majority of repairs if a high quality resin is used.

[screenman]

Whilst agreeing with that which Brent has just mentioned I can see one possible fault with your technique and this is the alcohol swab. Try using this swab on a clean piece of glass and when the alcohol evaporates in lots of cases there is a slight film left, this film can and will inhibit full bonding. My method is to clean the pit fully with my drill using it as a powered scribe and not drilling into the damage just roughing it, I will then go with a small amount of normal resin followed by pit fill. This of course is after I have done full dryout's etc. I hope you get to the bottom of this problem as things like this can certainly be frustrating.

[ghost rider]

Great advice from everyone, but nobody said anything about cure time. It seems to take longer to cure deeper pits, at least I seem to have better luck with large pits if I let them cure a couple extra minutes. I would like to hear Brents official cure time, please. Also, when scraping, make sure the razor blade is sharp and you are not too aggressive. Most pit resins are a little flexible when cured and you could be pulling the resin loose by scraping too hard.