One of the best-loved products of Japan's expert scratch-builders, Mori Mori putty is a high-quality putty for use in creating basic shapes, or the "core" of a something which you then tool into the final shape, as well as for traditional gap-filling purposes. A very small amount of hardener (2%) is added, then you knead the putty well and you have a 6-10 minute time frame where the putty is workable. Completely hardens to toolable condition in 25-40 minutes.