Maybe it exists a special tool to unseal the pistons; I don't know.
If you have to do it, I recommend to use the smallest screwdriver you could find (such for electronic components).
When the piston comes sealed to the glass, the aluminum foil makes like flower petals; you relatively easily can stick the screwdriver in one of the interstices.
When the screwdriver is in, you can gentle work parallel to the sealing; using the screwdriver as a lever to spread the aluminum foil from the glass.
It's not necessary to spread the whole sealing. 1/2 to 2/3 is enough.
Then, pass the screwdriver perpendicularly and pull. The whole thing will pop just like a beer cap.
Don't use knives or pointy things, due to risk of injury; and be careful.
But I think now of another method using a glass knife (I'm not sure how it is called in English), to cut the top of the bottle.
I only tested on pieces of glass; not on bottles. It's really efficient. Make one pass, applying a reasonable pressure; gently tap where you have passed the tool and the glass breaks net and clean without debris.
Back in the 80's, remember Mr. T advices, "believe in yourself, drink your school, stay in drugs, and don't do milk!" or something like that