Two smooth mica plates slowly approach each other in a calcium solution. At a distance of fifty nanometers, an invisible barrier suddenly appears between them: as if someone had stretched a web of molecules between the walls. This web prevents the plates from touching, even though by all calculations they should slide freely toward each other.
Chemists measured this repulsive force with an instrument that senses pressure to within a tenth of a nanometer. In a calcium chloride solution, repulsion appeared at gaps from ten to fifty nanometers. The standard theory for charged surfaces fails here: it predicts a much weaker interaction at such distances. The force turned out to depend on speed: it is weaker during slow approach and stronger during fast approach. This is not how a spring behaves, but how a viscous fluid does: the faster you try to compress it, the more it resists.
A network of calcium ions surrounded by water forms at the mineral surface even in an unsaturated solution, where the salt has not yet reached its solubility limit. The surface stabilizes this network and thereby prepares the ground for a future crystal. This explains why calcium carbonate crystallization so often begins on container walls or in bone tissue pores, even when the solution itself is far from saturation. Understanding this process could help control crystallization in carbon capture technologies and create materials similar to natural nacre.
The viscosity of the discovered film is only seven times greater than that of pure water, but that is enough to make the repulsive force between mica plates tens of times stronger than the classical prediction.