I am in Vancouver - but have a significant and growing prescence in Mexico. I am in the middle of a major architectural restoration and expect to relocate once the project is finished, and I've got every last bit of mush from the trough. Then begin an endless summer (back and forth Vancouver and Mexico)

Believe me - no one except us contemporary romantics, wants their fresco to crack intentionally. I didn't know about the widespread cracks. SOmetimes, we run across cracks from road vibration or minor earthquakes too. The cracks are more likely to be caused by too little sand, or too fine sand. Cracks are caused by shrinkage or by physical disturbance

With the sand - the size is as important as much as its cleanliness and sharpness. We build concrete with large rocks, and then the layers get finer and finer sand towards the surface. If you want a slightly gritty final layer use 20/30 sand. If you want glass smooth use 00. The limestone sand, or dolomite sand, is chemically the same as marble sand - its all calcium carbonate - and then the minor impurities.