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this single point on the surface and radiate outwards. Cleaning the instrument's
base and surroundings will correct the problem.
Incomplete
disk
This symptom causes disks that have the shape of a moon crescent, i.e. a circle
with a missing section.
It is caused by the mold not containing enough flux, or by the mold not being
leveled. Level instrument/mold holder or add flux accordingly.
Non-
homogenous
disk
When holding the glass disk in front of a light source, if you can observe powdery
residues, then some sample may not have dissolved.
Sample is not fully oxidized
As we know, un-oxidized sample cannot be dissolved in flux, and will also cause
damages to platinumware. Make sure to use the proper type and amount of
oxidizer.
Oversaturation
A fusion being a dissolution reaction, it is perfectly possible to obtain an
oversaturated bead. Simply reducing the amount of sample will correct the
problem.
Improper grinding
If the sample is too coarse, or if it lumps together easily, then the time allotted by
the fusion program might not be long enough.
One can either extend the fusion duration, or grind the sample to a finer
granulometry. We recommend smaller than 100 µm. Also, a manual mixing of the
sample with the flux can often prevent the lumping issues.
Sometimes, the small "dust" is actually gas (see below).
Bubbles in disk
Typical with carbonate samples, this phenomenon exhibits gaseous bubbles that
remain imprisoned within the glass disk.
In many cases, simply placing the sample on top of the flux and not mixing will
allow the sample to de-gas and thus avoid this problem. However, some samples
are known to make lumps and become harder to dissolve if not mixed; if that is
the case, then simply allow a period of slow mixing for an extra minute or two,
just before pouring.
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