How do i heat -seal properly?

Although heat-sealing cryo straws properly may seem easy, it can be a major source of problems, even for the experienced lab. Please review this material to ensure you are getting good heat-seals.

Exploding straws are the result of faulty heat-sealing or a crack or break in the straw itself. There are 2 basic faults when heat-sealing. The first is not using a hot enough setting on the sealer. This can be easily corrected. The second is damaging the straw during heat-sealing, sometimes by using too much heat. This is the only way a straw will explode.

Liquid nitrogen seeps inside the straw through a faulty seal or crack and then expands quickly upon warming the straw. If the crack is large enough the liquid nitrogen will simply shoot out the opening. The end result is that the cells inside the straw are usually lost or dead.

This occurrs by not heat-sealing with enough heat to melt the straw together. Upon rapid cooling by plunging into liquid nitrogen, the plastic straw shrinks rapidly and can separate, in part or along the entire seal.