What are the differences between spin cast pewter miniatures and rapid prototyped plastic miniatures? Here is a brief comparison:
The first big difference you will notice is detail... lots of detail! Rapid prototyped models have much more detail because they do not suffer from any restrictions on overhangs and pockets, so items such as gun barrels, cranes and catwalks can be depicted without the unsightly supports needed for spin casting, especially at larger scales (short of kit assembly). Cast models on the other hand, can have very little in the way of overhanging details (called cutouts) that would damage the mold during extraction. Even many pewter WTJ Naval miniatures with military masts have experienced mold wear due to the mast tops being pulled free of the rubber, so the tolerance for cutouts in metal castings is very low. Rapid prototyped models have no such problems.
You will also notice that rapid prototyped models have no flash, sprues or parting lines - no trimming! Being made of plastic instead of metal, they are not quite as proof against shock as pewter models and bottom flatness does vary slightly, however nearly all gamers that we have canvassed mount their ships on bases, and so the flatness issue has no real effect - they glue them down anyway. As for strength, the plastic used is a type of ABS, which gives a good strength even for very fine features. During testing and development of these ships, I commonly kept several RP models rattling around loose in a sealed tupperware tub; nothing happened to them despite weeks of tossing around. I recently tested a 1/1500 scale Sissoi Veliki by dropping it upside-down ten times from a 10" height onto a hard plastic picnic table and nothing broke (do not try this at home, dropping a model could still possibly break something and we do not recommend purposefully stressing standing features).
Both types of models should be cleaned before painting; the pewter should be cleaned to eliminate mold release and rapid prototype models should be cleaned in liquid detergent to eliminate wax and oil residue. A brush will be needed to help clear soft remnant wax left over from the building process.
Ultimately, the best thing about the plastic rapid prototyped models is hinted by the title itself: Rapid. The time from completion of a ship design to the time it can be printed is minutes, which says it all about the future of WTJ Naval as we continue to release models as quickly as they can be designed.