This is the data sheet from Chavant Description Chavant NSP clay is a globally well-accepted non sulfur modeling clay used by the Special Effects and Fine Arts industries. It holds exceptional surface details and is somewhat waxier and tougher than other Chavant products.  Available in: Soft, Medium, and Hard Colors: Green*, Brown or Tan (Tan color will vary) *Green color is different at each hardness. PACKAGING: 2 pound block, 10 pound block* *soft & medium only NSP was introduced in 1993. The intention was to eliminate the sulfur filler in a professional grade sculpting clay, which often caused inhibition problems with various liquid rubber mold-making materials. The NSP product line consists of clays that contain higher percentage of wax components making the clays somewhat “tougher”. Available in Soft, Medium or Hard, these clays have good adhesive qualities, flexibility and length. Because they are “tougher” NSP tends to accept cut detail lines very cleanly, with no ragged edges. The surface texture of NSP will be somewhat “grabby” when compared to sulfur-based clays and even the NSP – Soft is rather firm by some people’s standards. NSP is commonly used by artists for the creation of sculpture and is often used to fill cracks in industrial patterns or to build dams when making splash molds. Product designers who freehand sculpt also use NSP. NSP is subject to surface oxidation. If the clay is in its original package it will have a long shelf life, certainly months and probably years. If the clay is repeatedly heated and cooled, oxidation is accelerated. Sometimes this characteristic is beneficial in handling or mold making since the surface can become harder. FIND A DISTRIBUTOR Unique Properties NSP can actually be melted and poured as a casting, brushed or sprayed.  Physical Properties NSP Soft and Medium Density: 96.7 lbs./cu. ft. Specific Gravity: 1.55 g/cm   NSP Hard Density: 103 lbs./cu. ft. Specific Gravity: 1.65 g/cm   Softening Temperature 150°F / 66°C Troweling Temperature 175°F / 79°C Brushing Temperature 185°F / 85°C Casting Temperature 205°F / 96°C Hygiene  Wash hands with soap and water after use.  Handling Tips NSP can be warmed to soften but as it softens it also becomes sticky. Using small amounts of water, citrus-based solvents, lighter fluid, latex paint removers, turpentine or mineral spirits as a lubricant on the surface of the clay will help to attain a smooth surface.

Not sure if you still need an answer for this - but kind of clay did you buy? If it's oil based clay like Monster Clay and you want it more malleable, I just put a fresh/mostly full tub in the microwave for 2 minutes (maybe just a minute for half-full tub). Depends how soft you want it. If you overcook it in microwave (I often do...), you might find it goes to hot liquid in the middle. If that's the case, I usually just set it aside for a few minutes and try to resist the temptation to stick my fingers in it.