Hi all,
In your opinion Having no visible moisture on the leaves is not going to damage the plant and 'dry' it out ??
No, not if you have 100% RH. What causes the damage to the leaves of the plants, and stops cuttings rooting, is when moisture is lost more quickly from the leaves than it can be replaced by the transpiration stream through the xylem from the root to the leaves. What defines the rate of the transpiration stream is the differential in humidity between the air inside the leaf and the air outside. If both are close to 100%, there isn't any water loss.
The "dew point" is one way of doing this, other ways are the mist or fogging units that they use in commercial horticulture. A mist unit works from an "electronic leaf", this is basically 2 electrodes mounted on a plastic block, when there isn't any moisture on the sensor, no current flows between the electrodes and the mist is turned on. As soon as the surface of the sensor is wet, current flows and the mist turns off. On a day like today the mist would be coming on every couple of minutes, on a damp day in December it might not come on at all.
A fogging unit typically gives slightly better results, in this case the mist is extremely fine and gives both moisture and evaporative cooling. One problem with some cuttings in fogging units is that they don't actually "realise" that they are not connected to their parent plant, and for this reason don't form callus or new roots.
If you use the dew point method, like "Foxfish", you will be less prone to moulds and algae on the plant leaves etc.
Cheers Darrel