Step 5: Cooling |
Perhaps the most critical step of the fusion process, the cooling rate of the fusion bead must be carefully controlled to lock the fusion in an amorphous glass phase. If a sample is cooled too slowly, the fusion solution may crystallise, but if a sample is cooled too quickly, the bead can crack or burst because the internal stresses are too high.
As the moulds are individually withdrawn from the hearth, they are placed over a controlled cooling fan that dictates the cooling rate of the mould. A mould release agent can be applied at this stage using our unique iodine caps.
An optional annealing step can be added for difficult to fuse samples. This step reduces the internal stresses that can cause cracking of the bead. Once cool the beads can be handled and labelled on the non-analytical face and are ready for analysis.