"BTW, one of the real tests of any WPD (waterproof down) chemical is how much, if any, does it reduce teh roiginal loft. Tough to pay for natural down of 800 fill when the WPD treatment makes it 700 fill."
I do not think it effects loft.
From DriDown's web site:
"...While down of a specific fill power is the same across the board,..."
This and other questions need to be answered. Unfortunatly, it is only being offered on low fill downs, ie 550/600. The best I have seen *is* 800(EN or American?)in some jackets, but there is no spec on the actual starting fill, before treatment, that I have been able to find... Nothing that says it reduces loft. Nothing that says it increases loft. I think this would change slightly if it disrupts or enhances the static electricity repulsion, but not by a measurable amount...especially given the variability of down plumes.
Richard, from DriDowns web site I get this:
"...Apparel and sleeping bags insulated with DriDown™ will perform better right away. Even small amounts of sweat or humidity will begin to diminish the performance of untreated down. DriDown™ will keep even the smallest amount of moisture from negatively impacting down performance."
"Untreated down plumes collapse when wet, reducing loft and insulating efficiency. DriDown’s™ water resistance far exceeds that of untreated down, staying dry 10-times longer in the presence of natural body moisture, humidity, rain, and snow to offer superior loft and thermal efficiency in any environmental situation."
I am not sure they even understand the difference between water vapour (gas) and water (liquid) and ice (solid.) As with many people, they could well be confusing water (liquid) with water vapour(gas.) Nor, do they understand how water vapour changes phase to a liquid.
Example: Glass is a pretty good water proof material. Yet condensation on windshields still happens.
Example: Silnylon is quite hydrophobic, but, we get condensation on it. (Worse, the droplets are quicker to come off.)
I strongly suspect it could reduce the actual formation time slightly by reducing the number of "seed" sites available. But,it doesn't really matter. Dridown does not protect the down from water in a long term wet-out, anyway. It is NOT a total water proofer for down. More like a DWR coating on the plumes. I would expect some sites to be closed, but, there are literally millions of seed sites within down, treated or untreated. Water molecules have an afinity for other water molecules, indeed this causes condensation, soo, I expect condensation to occur in dridown about the same as normal down. Only the adhesion or "stickiness" of water is *clearly* different. The condensation droplet will be rounder, since, it will not wet out the plume, allowing it to stick. (Other ramifications...)
Example: Condensation on glass. If treated with RainX, it will bead. If untreated the bead shape is different. But, it still happens.
Only the rate of formation will be slightly different. Likely, a reduced amount of vapour will condense, but the difference is surely minimal. Condensation will occur in the down. But, since it does not wet it out as fast, there will be some noticable benefit from reduced drying time. And, since the plumes are hydrophobic, it will not wet them, saturating the plume's molecular structure. Again, reducing drying time for this aspect.
Local supersaturation is likely to foster movement to outer layers, per normal for all down. It will migrate to the colder layers nearer the outside of the bag due to vapour<->water equilibrum from the surface area of the droplets. I suspect that the more spherical shape will slow this migration.
Other statements about DriDown can be seen here: http://www.dridown.com/faq/