Rapid Prototyping involved creating a working model of various parts of the system at a very early stage, after a relatively short investigation. The method used in building it is usually quite informal, the most important factor being the speed with which the model is provided.
There are water-and solvent-based -- also called oil-based -- polyurethane varnishes. Water-based polyurethanes are more environmentally friendly and safer to use than solvent-based, but they are not as resistant to wear and tear as solvent-based products.
There are very few resin and varnish systems that can provide the ease of use, appearance, dry time, early mar and scuff resistance, abrasion resistance, and household stain and chemical resistance of a solventborne oil-modified urethane varnish.