(Inside Science) -- Remember Silly Putty? That thick, elastic lump of goop that you could stretch and squash every which way? For most of us, it’s a fond childhood memory.

But Silly Putty is more than just a fun toy. Its unique physical properties are similar to those of Boger fluids. They’re an odd class of materials -- pull them apart slowly and they’re elastic and soft, but pull them apart too fast and they stiffen up like a solid. The unusual fluids are named after David Boger for his discovery of constant viscosity elastic liquids.

Rheology is the study of the flow and distortion of materials. Boger came into rheology during a challenging but exciting time in the field. Researchers were trying to measure polymers, which include a wide range of things from DNA to proteins to all kinds of plastics. The research led to advances in the study of Boger fluids that had impacts across industries, like helping design pesticides that stick better to leaves instead of dripping down to the ground.