Colloid, from the Greek κόλλα (glue), refers to a dispersed phase of a two-component system in which the elements of the dispersed phase are small enough (i.e.: ≲ 10 μm) to be affected by thermal forces. In colloidal science, the so-called DLVO theory (named after their establishers: Derjaguin, Landau, Verwey, Overbeek) is the most employed theory to explain particle union. It consists in a balance of attractive van der Waals (vdW) and repulsive electrostatic double layer (EDL) forces. These colloidal forces are present in a variety of domains, ranging from cheese production and blood coagulation to industrial paint manufacturing. Colloidal forces are of paramount importance in dictating how these mentioned processes take place.

Molten silicates containing suspended crystals are of extremely importance in natural and industrial scenarios. In the former, these complex silicates are one of the most important geomaterials in volcanology. In the latter one, silicates containing suspended crystals are extremely relevant in nuclear waste vitrification. In silicate glasses and melts, there has been observed evidences of colloidal forces through several properties and features. Here, we bring a variety of evidence, ranging from structural modifications to abnormal viscosity behaviour of specific family of crystals (platinum-group element) suspended in silicate melts. It is observed that for these specific silicate melts, viscosity could increase of up to ~5 orders of magnitude just due to crystal aggregation, process which in turn is controlled by colloidal forces.

In both volcanology and in glass science, the understanding of the existence of these colloidal forces, together with the effects, particularly on viscosity, will certainly allow us to better understand magma dynamics as well as to enhance our understanding on glass melting processes, such as nuclear waste vitrification processes.