Monday, March 8, 2010

High Viscosity

Colleen Putnam, in a December post originally found on Lifestyle and then cross-posted at Zimbio's rheology blog followed up on a money-saving discussion started at Consumer Reports.  The first CR article discussed how much of a commercial product could be left in a container.  The second article described how to pull the remaining product out of the container.
Colleen identified a rheological theme among the commercial products--
The science of rheology, the study of flow, explains how thick, gooey things move differently than smooth watery things. It's a physicist thing. For the non-Newton layperson, it explains why the toothpaste tube, lotion dispenser, and ketchup bottle always have product left at the end that never seems to want to come out. 
As I thought about this comment, something started to bug me.  The main issues with the products (skin lotion, laundry detergent, condiments, and toothpaste) is not how they flow, but how they don't appear to flow.  Simply put, the viscosity of these materials is high.  That is why these materials stay in their respective containers.  Any non-Newtonian flow properties (pseudoplasticity, thixotropy) aren't as important as the viscosity at low shear rates.  For more evidence of this, just see to remove the product from the containers: dilution.  Add the appropriate solvent, reduce the viscosity, and you're on your way to saving money.

1 comment:

  1. Why the over explanation invoking rheology when a simple 3-D Navier-Stokes representation will suffice? No idea.

    Heat is always another idea, but I don't want to suggest that as I can imagine someone will burn their house down trying to get an extra $0.43 worth of beauty cream out of a tube.