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How to Use Jacks & Pacioffis in Glassblowing

Learn how to use jacks and pacioffis from glassblower Ed Donovan in this Howcast video.


Hi, my name’s Ed Donovan and I am here at DC GlassWorks. You can find us at We are a public access glassblowing facility, we also do metal and metal casting and welding. We are primarily a teaching facility. We want to share with people the magic of glassblowing. It’s an amazing substance and today, I’m going to be talking to you about glassblowing. Uh, using the jacks in glassblowing is uh a difficult skill to learn. Uh remember glass is a liquid and it’s very, very hot and it should be pretty fluid when you’re using uh when you are working it. Uh, so the jack's primary purpose is cutting in what we call the jack line which is essentially the, the constriction at the end of the pipe or the top of the bubble that you're gonna use to separate the vessel from the blowpipe on to the punty. Uh, it’s also used for shaping the sidewalls uh the handling of the jacks is your uh open palm with your fingers wrapped around one handle with your, with your thumb on the other and your very, very gently squeezing into the glass as your rotating the pipe and the rotation of the pipe is critical. You never want to stop rotating the pipe if you do stop rotating the pipe or when you come to the end of the bench and you need to reverse your rotations you want to let up on the pressure of your jacks just a little bit so that you don’t create any kind of a flat line. Remember we’re working rounds and our jacks are flat, they’re just two blade straight edges uh, so your rotation is very important in keeping a round uh surface of your glass by the rotations. Uh so the other use of the jack is as a cooling device very similar to the marver table. The back of the jack is a flat metal uh so you can use that to shape the bottom or cool the glass in a location that you need to uh remember steel takes heat out of glass very quickly. Uh, then we also have what’s called a pacioffis, which are also jacks but they’re a wood blade as opposed to a metal blade and uh they’re used uh primarily in shaping bowls because they don’t take so much heat out of the glass and they’re a little bit gentler they have a a more dull or blunted end uh so that they’re not digging into the glass in in making bowls and your trying to make a very nice even gradual shape on the sides of the bowls and it would be very difficult to do that with a very uh straight and pointed metal tip so we use a wooden tip instead for uh bowl formation.

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