1)XRF fusion bead Preservation

Most XRF fusion bead are somewhat hygroscopic. The most hygroscopic is prepared by Na₂B₄O₇, covered with a layer of white hydrate. Lithium borate flux is less affected by humidity. In any case, samples to be tested should be kept in the dryer, especially the standard material.

2) XRF fusion bead rupture

XRF fusion bead rupture is related to many factors:

• The amount of demoulding agent is not enough, so add more before fusion. But if the problem still exists, add more before casting, especially for Fe, Cu, Ni and other samples.
• There is glass residual or external particles in the mold.
• The sample was not completely dissolved.
• Crystallization occurs. If a small white spot appears during cooling, the flux is a deviating optimal combination.
• If bubbles can be observed on the flat side of the glass bead, there is residual graphite in the sample.
• The cooling fan started too early.
• There is airflow around the mold during cooling.
• The mold is too cold.

3) XRF fusion bead burst

XRF fusion bead with internal stress sometimes burst usually after operation or prolonged cooling. The stability of the glass bead can be increased by adding a small amount of SiO₂ or Li₂B₄O₇ to the flux mixture. The factors that cause internal stress are:

• Insufficient demolding agent.
• Short time for natural cooling before forced cooling
• Not optimal flux combination

4) Crystallization during cooling

XRF fusion bead crystallization is unfavorable, so it should be avoided in preparation. The factors include:

• The flux combination is not optical, and ensure the best composition.
• The mold temperature is too low during casting, so strengthen control to the mold temperature.
• Flux particles splash onto the mold, and it is suggested to use dust-free flux.
• Nitrate or carbonate particles spatter onto the mold, and it is necessary to weaken heating during oxidation.
• The invisible spot particles in the corner of the mold may also cause crystallization. This can be judged by observing whether the crystal appears in the same position during repeated melting. Cleaning the mold is an effective means of eliminating such crystallization.

5) Ejecting of melting mixture from the crucible

This problem is caused by humidity, hydration or carbonate and can be solved as follows:

• Use dehydrated flux with coarse particles.
• Appropriately slow down the heating speed of carbonate.
• Do not mix the sample with the flux, but distribute it to the top of the flux.

6) The apparent insoluble black spots floating on the bead surface

The black spots indicate the presence of graphite, and handle this as follows:

• The sample is mixed with an oxidizer and the flux is placed on top.
• Spray air into the crucible.

7)Bubbles continuously formed at the bottom of the crucible

This may be caused by the decomposition of SO₃ in the melting body into SO₂ gas. The following measures could be taken:

• In presence of sulfates, use the flux of Li₂B₄O₇/LiBO₂ = 50/50.
• If sulfides exist, they may be treated like melting sulfides samples.

8) Bubbles on the bead surface

If bubbles appear, do as follows:

• Nitrate or carbonate particles splash on the die during the oxidation step, so it is necessary to reduce heating.
• Add more demoulding agents. If possible, extend melting time or increase melting temperature.