home made pyrex pieces

[wafflemanwillis]

lately ive been experimenting on making my own pieces using pyrex lab equipment and a blow torch. i made a sick big pipe out of a beaker. wouldve been perfect for a bong but i dont know what to do for a good stem and bowl. the beaker just had an indentation for a bowl and another hole for a carb. i let my friend have green hit because he was stacking. as he was taking the hit an inch long crack formed starting from the middle of the bowl and by the time he was done it had expanded to at least 3 inches long. i tossed it before it like exploded. i would love to make a bong before summer gets here, only a week and a half. i have access to various pyrex equipment, especially test tubes. i dont want to drill unless absolutely necesary.
any ideas on how it should/could be done are welcome and any ideas on what caused the crack and how it can be avoided would also be appreciated.