Stem Head Pressure on Large Star Breaks

[Sneck]

Stem Head pressure (the pressure of the injector seal against the glass) can be quite a critical issue in star breaks.

I just did a HUGE star break this afternoon and all but one leg filled nicely. I flexed the stubborn leg NUMEROUS times but just could not get the resin to flow down that leg. It happened to be a leg that was about 1-1/2 to 2 inches long, so I drilled and popped a mini bullsey at the end of the stubborn leg, then filled from that point, but the leg did not fill all the way. It still had about a half inch to go but would not go any more.

As I backed off stem pressure to the point that the injector was no longer touching the glass, the last bit of the crack started to fill on its own with the the residual resin that was either in the break, or it was resin from what was left on the outside glass. A moment or two later and the stubborn leg was completely filled with no mounting bridge or injector on the glass.

I think that since this was a quite large star break with long legs that it was naturally very sensative to stem pressure and even though the stem was just barely tight enough to keep the resin from seeping out, it was enough stem pressure to choke off the stubborn leg.

The HUGE star break ended up looking GREAT! Customer was very, very pleased and I was happy about the repair too.
Moral of the story on this one is... "Reduce the stem pressure". It could make all the difference in the world!

[tooldini]

Thanks,, that could have been my problem on a repair I did a couple weeks ago same thing you talk about,, I never got it done right really but they were happy anyway LOL. She just wanted it to look better and hold up for a while. Next time I will remember that maybe I had too much pressure.

thanks
Jeff

[screenman]

On some starbreaks the legs will be up near the surface of the glass and stem pressure will certainly effect these. To check just put slight pressure on the legs with your probe if the appear to shut they are surface breaks if they open. If I have not explained this properly please tell me it is a important part of break recognition It helps greatly if you know what the break is doing before you start the repair.