Originally posted by grymg
Thermal printing is definitely the ticket!! That way it's water proof and scratch proof. My experience is if you simply print the decal onto the top layer of the sticker then it can still easily be scratched off.
Water proof yes, scratch proof no. Although thermal printed decals are much more durable than then the inkjet decals most people make for themself they are by no means scratch proof. With a thermal print the the print is still placed on the print surface and as a result can be scratched. All those who have used F1 tech, AMS or even the Tamiya decals can probably recal a sticker that at some point had a portion of it scratch out or accross some other part of the decal.
For maximum scratch protection I would suggest placing a clear layer over the decal to provide an extra durable overcoat that would have to be scratched through before the abrasive could contact the decal itself.