Fusion Troubleshooting; Disk Cracks; Disk Crystallizes - Katanax K2 Prime Manual

This section presents the most common fusion-related problems. For specific
assistance, please do not hesitate to contact us (see page 91, Contacting
Katanax).

Disk cracks

Disk cracking occurs when there are internal stresses within the glass bead. The
specific causes can vary as follows:
Glass disk sticks to the mold
If disk top surface is concave (disk adheres to the mold walls), add non-wetting
agent at the beginning or during the fusion. Katanax recommends lithium
bromide.
Glass disk contains undissolved particles
Some sample may not be completely dissolved. Make sure that sample is fully
oxidized or decrease amount of sample.
Glass disk is improperly cooled
Generally, cooling a disk too fast can cause its cracking. Allow more time for the
still-air cooling (i.e. before starting the cooling blower).

Disk crystallizes

Crystallization reaction cause the transparent melt in the mold to become milky-
opaque during cooling, typically from the edges towards the center, pushing the
still-liquid melt to the center and upwards as crystallization progresses, thus
creating a volcano-like structure.
Inappropriate flux
Crystallization will occur if too alkaline a flux is used (i.e. too much lithium
metaborate). Increase the proportion of tetraborate to compensate.
Improper cooling
Natural convection (still air) cooling is too long or too short. Edit convection
cooling duration parameter manually.
Generally, crystallization occurs when the natural convention cooling is too long.
External contamination
In some circumstances, dirt, dust or other small debris can be sucked into the
blower and land onto the glass bead. This type of crystallization will develop from
troubleshooting
Fusion
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