Hopkins seal

The term Hopkin's Seal refers to when an item being sealed into an outer jacket is held in place with a holder (cork on a stick, ect) and the outer tube is collapsed to meet the item being sealed.

So, say you wanted to fabricate a quick gas bubbler.

•Begin with a piece of 38mm on a blowipe •Flare a piece of 10-16mm (whatever the sketch calls for..) to meet the inner diameter of the tube as closely as possible. It is VERY important that you get the flare very close to the ID. To reduce sharp angles where the jacket meets the 16mm I try to get as close to a 90* flare as possible. •Use a cork bore to make a hole that the inner tube can slip in to be held (or make a hole in the cork that allows a smaller piece of tube to slip through, then into the open end of the inner tube). (or use cardboard..) •Heat the ring of tube that the flare touches, and if all has been set up correctly, the outer tube should collapse down slightly and make a complete, clean seal with a thin ring of perfect contact.

good luck!