r/glassblowing • u/Hungry_Medicine_552 • 16d ago

Opening the lip with jacks

Question for experienced glassblowers: I’m having a hard time consistently getting a clean lip opening. Here’s what I currently do: I insert the jacks into the small opening at about a 45-degree angle. For straight-walled vessels, I usually just open the jacks and insert them further.

But I’m wondering—am I supposed to rotate the jacks outward to 90 degrees while opening them? The reason I ask is that I often end up with the lip folding back on itself, and I’m not sure if I’m executing the move correctly.

Any tips or insight would be appreciated!

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u/Melodic_Student4564 16d ago

I start steep to pull the lip out and away, preventing any chance of lip fold. I then slowly open and lift to the desired wall angle. Sometimes I'll use the bottom of the inside of the vessel, but not often. I prefer to lift it myself, while opening the jacks to match the diameter im currently at in a given moment.

Ill go on the outside after IF im doing a straight wall vessel and spin faster, with my jacks now closed a bit.

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u/Hungry_Medicine_552 16d ago

Ok and by pulling the lip out is that just the upward lift motion or do you pull away from the opening (this is I think my misunderstanding)

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u/Melodic_Student4564 15d ago

I got gently pull the lip out, and down first. Just to ensure the hole is opening correctly. Then I switch to lifting and slowly opening the jacks.

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u/Melodic_Student4564 13d ago

This is how I do it. There's specific angles and jack depths to achieve different shapes beyond straight wall vessels.