Question:How do I fill a subsurface crack?
The definition of a subsurface crack is a crack in the outer layer of glass that does not open to the outer surface of the glass. Short cracks (1" or less) radiating from the impact point of a star break or combination break sometimes fall into this category. Long cracks, regardless of where they start, rarely if ever fall into this category. So to answer the question we must assume we are not repairing a long crack which requires a different procedure, and that there is no damage to the inner layer of glass which Delta Kits does not recommend repairing.
While many injection systems are incapable of repairing subsurface cracks, they may be filled quickly and easily using a Delta Kits injection system. If a Delta Kits injector is used according to the company's instruction manual, in most cases the basic procedure used to fill a star or combination break will fill subsurface cracks without any additional manipulation, it's simply a matter of alternating between pressure and vacuum until the air in the crack has been replaced with resin. In some cases applying light pressure along the crack with a steel probe, from either the inside or the outside of the glass, will help speed up the process, but is usually not necessary.
If you are using a Delta Kits injection system and experiencing difficulty filling subsurface cracks, we encourage you to call and chat with someone on our customer service team to help identify any procedural issues that may be affecting performance.