The easiest way to see if undissolved material is still present in the glass bead is by viewing it under a stereo microscope. The fusion is performed on a fluxer and takes on average 25 minutes. Different types of fluxes were discussed. It is also good lab practice to check the quality of flux obtained from different batches. In general, if the fusion load is high it is best to purchase flux in bulk manufactured from the same batch.
Differences do exist between batches, even for pre-fused flux.
The 12-22 flux has been found to have a high LOI, which could be problematic. The problems associated with the analysis of chromites by the powder briquette method were discussed. Another problem experienced is segregation within the pellet due to grain size effects. The definite need for type-standards was discussed and actual examples given of analysis of samples that had concentrations within the range of the calibration standards, but which were of a different mineralogical make up. The analysis was completely wrong simply because the mineralogy differed.