Large Pit Question

[Bois]

It seems that whenever I encounter a large pit opening and have to fill it in with pit resin, cure and then drill a small hole so the injector will fit, the pit resin traps air around some of the shattered glass pieces and it looks like pepper specks. I'm able to complete the rest of the repair OK but the pit hole looks ugly. Since I can't use a pressure/vacuum cycle when reducing the size of the original pit opening, what, if anything, can be done to reduce or eliminate the tiny air specks? I had one today that had a quarter size "daisy" break.

[Brent Deines]

I'm not sure I have much helpful advice on this one as I can't say I have experienced this problem, but when there are air bubbles in the pit resin they will sometimes show up in the break, especially after curing, which is why we always recommend storing the pit resin upside down prior to doing the repair. In addition to storing the bottle upside down it is important to keep it in that position while removing the cap and applying the resin.

Although we tell technicians over and over again, in training classes we see the bottles being turned upright as they remove the cap, thereby allowing air into the tip, and the longer a technician has been doing windshield repair, the harder it is to break them of this habit, myself included.

This may not work for all pit resins due to viscosity variances in competitor products, but it does work quite well with Delta Kits Premium Pit Resin and Premium Plate Glass Resin.

For whatever reason we have had a rash of breaks with large pits in our practice glass used in training classes over the past few months, so we have had the opportunity to train a number of windshield repair technicians using the fill and drill method used when working with large pit areas. To the best of my knowledge none of those repaired in the training classes had air specks in the finished repair.

I know it's a long shot, but sometimes it's the simple things that make all the difference, and anything below the pit resin should be filled just as easily after capping as it would be if capping had not been necessary.

[toab]

Bois: Look in the recent archives under "old school repair methods" for another approach to big pit repair.

[Bois]

Toab, thanks for the reference. I knew I had seen a recent thread on large pit repairs but couldn't find it earlier. Otherwise, I would have expanded your thread.

Brent, thanks for the response. However, my problem is not with air bubbles in the pit resin but air particles already in the pit area around minute pieces of broken glass (even after I clean the pit with my probe). The repair I did today had an oval shaped pit about 3/16" X 5/16" wide - just wide enough that the injector seal would not cover. I tried to place pit resin at the ends and keep the center exposed but the resin ran. After curing, the pit looked liked I had sprinkled pepper into the pit before applying pit resin. Anyway, I'm assuming that the black specks are air particles. Maybe I should place my curing tab over the resin and massage the tab a little. Maybe that motion will help lift some air. Another thought is to carefully drill out more of the loose glass particles before applying the pit resin. Who knows...

[Daveycrewcut]

I suggest you go back and read Brent's post. When you first apply pit resin to the pit area and before you apply the curing tab, make sure there are no air bubbles in the pit resin. You can use a needle or probe to remove noticeable bubbles. Since a certain amount of linear shrinkage occurs during the curing process, small bubbles can appear bigger after curing.

If you do like Brent says, the resin should come out bubble free because the bubbles will have floated to the bottom of the bottle (which should be up).

Never shake resin bottles! or you will have air bubble problems.

[Bois]

OK, guys! I'm not being clear. The air is not in the pit resin. The broken glass beneath the pit resin has black specks. Almost similar to what a crack looks like when all the air is not removed.

When we do a repair we use an injector so we can do a pressure/vacuum cycle to remove all the air. When you just add pit filler to close in a large pit opening (so that we can use an injector) we don't use a pressure/vacuum cycle, thus leaving some air beneath the cured resin. The pit resin flows around this air and traps it when cured. Keep in mind that I'm referring to smashed glass in the pit area.

[Brent Deines]

I understand what you are saying, I just haven't experienced it.

Are you using Delta Kits pit resin? If not, what is the viscosity?

It sounds like maybe the problem could be solved by going to a higher viscosity. Our Premium Plate Glass resin is a much higher viscosity and should not seem into the tiny air spaces in the smashed glass. That way you inject your MagniBond, or whatever low viscosity resin you use into the break, enabling you to utilize your pressure and vacuum cycles to remove those tiny air bubbles.

I know some people like to drill out all of the smashed glass, but in most cases my experience has been that the end result is better when it is left in tact.

[Bois]

Brent, I have some of Delta's plate glass resin. I'll try it the next time I have a bad break. Thanks.

[mrchip]

if not a new daisy break ...could it not be dirt particles?...just a thought