i thought maybe it was a mix or a hybrid between water based and plastisol maybe with combined properties... the "hydro" being the water based part and the "sol" being for plastisol... but i really don't know.
I've heard of Hydrosol before. It is an additive that they add to the inks. Apparently it softens up the inks to the point that they are close in softness to waterbased inks. I'm planning on getting a dozen made shortly. I'll keep you posted.
Here is what I found online. Can't remember the site:
Hydrosol Inks
Trade Name: TGL Hydrosol
Composed of Acrylic Copolymer, Alcohol and Wax. The viscosity is from 1000 PA to 1400 PA. The heat stability lies between 250 degree C and 300 degree C. The PH value will be 6.5 to 8.0. No film formation. It gives alternative effects to the discharge printing. No foil is being transferred in this method due to higher maintenance of Heat Stability at 150 degree C to 200 degree C. This is a very new special product introduced by The Global which has been well accepted by all buyers. The print which appears on the fabric will give only the fabric feeling and no separate print feeling. It can be printed in any fabric at any time.