Trapped air in bullseye

[thechipdoctor]

Sorry if this has been covered guys but I would very much appreciate some advice...........
I have been doing repairs on my 'practice' screen at home, I initially had trouble creating damages, so I used an automatic centre punch to make breaks, this made quite large 3 legged stars which I am now quite good at repairing.
To make a different type of break I created some small bullseyes by drilling and popping, now here's my problem!
When I tried to repair them, no matter what I tried, about one third of the damage stayed black and no matter how many times I went through the vacuum/pressure cycles I couldn't remove the last bit of trapped air.
Can anyone help????

[screenman]

Do you know what black is?

Have you tried backing the pressure off of the injector, not the piston. Have you tried a probe down the injector?

What kit are you using and how much training have you had and from whom?

[thechipdoctor]

Delta kit...I am from the south coast in the Uk, just down the road from Southampton...you probably have worked out who trained me!!
It's def something i am doing wrong, just not sure what....................

[Master chip]

Sounds to me you have placed too much pressure on the glass therefore trapping some air in the bullseye. Try backing off ever so lightly on the surface pressure and see if that helps.

[screenman]

That will teach me to put a post on when I have been up 20 hours, long day yesterday, sorry. Few tips here things here, not enough resin to create a hydraulic system, too much injector pressure, not leaving it long enough under pressure, sometimes a small break can take longer than a big break to fill.

[thechipdoctor]

Ok, so......i've just spent the last three hours practicing.
I completed two star breaks, one went so well I had real difficulty finding it after I'd scraped it to polish it.
I also drilled and popped 4 small bullseyes, i tried all the suggestions above, and still no success..............
Screenman, I will try and get some photo's to email you.....in the meantime, anyone got any other ideas?????

[screenman]

Try this with your mini bullseye, place a drop of resin in the hole and probe and push slightly with your slide hammer. All this without even putting a bridge on, let me know the outcome. Failing that place a bridge on put the injector on pressure 1 minute, off 1 minute then pressure for 10 minutes, then what happens.

[thechipdoctor]

sorry to sound a bit thick, do I do that, and then repair as usual, or just that, and then pit fill???

[screenman]

Depends if it fills or not.

[Nomad]

If you put a probe down inside the injector, it will have to be small enough to fit through the drill hole and contact the loose piece of glass you knocked out when you made the bulls eye. Press down to flex the loose piece a number of times and that should help a lot. If not, the last choice is to use the heat from a micro torch to heat the chip and then apply resin under pressure. Check for too much stem pressure as mentioned above. Do not put too much pressure on a hot chip or you will flower it. A sewing machine needle chucked in a pin vice may work for a fine tipped probe if you don't have anything else. A sharpened piece of spring wire or a hypodermic needle may work too. At swap meets (flea markets) they sometimes have these dental instruments with fine ends on them that might be adapted to go down into the throat of the injector.