It's an aliphatic resin, like Elmer's or Titebond, but it is different. It dries much faster and sand more easily. I think it must have something to do with both the solids content and the resin itself....

From Pica's website:

Gluit has satisfied model builder’s and crafts enthusiast for over twenty years. Its formulation, stressing quality over cost factors makes Gluit the strongest PVOH aliphatic glue in the market place. This standard of quality has proven its worth with Gluits ability to sand without gumming up the paper. Testing has always proven that Gluit out performs the "Watered down" glues in areas such as wet tack, assembly time, peel strength, shear strength and flexibility.

4 oz. $2.59
8 oz. $3.49
12 oz. $4.49

Gluit H/D 601 uses a higher concentration of solids and over twice the viscosity of our standard Gluit, making this adhesive ideal for those hard to glue fibrose materials. Gluit H/D 601 will will remain on the projects surface without "running down", insuring a stronger uniform, even bonding surface. The higher concentration of solids increases the performance properties when compared to any carpenters glue.