Why is cationic bitumen emulsion sometimes selected for wood and porous material treatment?

Cationic emulsions carry a positive charge that can improve wetting and adhesion to many porous surfaces that tend to be negatively charged or contain acidic groups. On porous materials, the emulsion can penetrate and then break, leaving a bonded residue that reduces water ingress. They also often break faster on absorbent substrates, which can help in practical application. However, performance depends on primer selection, moisture content of the substrate, and the specific emulsifier chemistry. A small trial area is recommended to verify penetration, tack, and curing without staining or blistering.