2 unrelated questions: rock wool and plant walls

[Ray]

I hate to do this Ocelaris, but my ceramic engineering background won't let me stop.

Both rockwool and fiberglass are silica-based glass fiber materials, but the formulas of the raw materials used in the glass melting process are entirely different. I suspect that in both cases, the idea is to use the cheapest available raw materials that give the fiber properties sought.

Rockwool products tend to have relatively short fibers, while insulating fiberglass strands tend to be longer.


All such glasses are based upon a silica "backbone" to which various alkaline earth modifiers are added to lower the melting temperature and viscosity. Pure SiO2 will melt at about 2000°C, but at that temperature, the viscosity is so high, you cannot work with it. By adding modifiers, you break the Si-O-Si bonds to improve the workability, but it degrades the durability of the glass.

The acid treatment of the fibers extracts the "dangling" alkaline species to adjust the surface pH downward, but it really has a relatively little effect on the hydrophobicity. That is usually controlled via coatings, and their adhesion to the glass can be affected by the surface chemistry.