Cold seals are those partial joins in glass, usually described as having acute angles: this is why glass artists are encouraged to make everything smooth, because it not only showcases the fluid qualities of the medium, it also makes for technically stronger pieces.
One of the dangers in making hollow beads using the ‘coilpot’ (i.e. mandrel wound) method is that, if those coils of glass get too cold after they're laid down (because, say, you're busy laying them down elsewhere in the bead, and it's kinda hard to stop and go back to warm the bead) they can pull away from each other, causing leaks or worse.
Another color is messy bead—not the yellow base glass, but the cream and pink stringer, which is composed of ASK104 and CiM respectively. But the bead didn't crack because of incompatibility, but rather operator error.
As in this example.
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