How Does the Viscosity of a Solvent Affect My Cleaning Results?

Viscosity is a chemical characteristic that describes a fluids ability to flow quickly, smoothly and without outside effort.  It is an indirect measure of the molecular attraction within a fluid for itself; highly viscous fluids are strongly attracted to their own molecules and resist separation.

In terms of critical cleaning, highly viscous fluids are not very good cleaners because they resist wetting the surface of the parts to be cleaned. Complex shapes and tiny parts are not well-wetted and therefore not well cleaned. In the table below, the viscosity of many popular solvents (and a few other benchmark fluids) are listed. Many halogenated solvents have viscosity scores far, far lower than water or alcohol. As such, they will clean much better than those other fluids.

Viscosity is a key component in calculating the wetting index of a solvent. The higher the wetting index, the better the cleaner perorms.

Here is a list of solvents and their viscosity:

Fluid Viscosity (cPs)
Air 0.02
Acetone* 0.30
AE-3000 0.34
Opteon™ SF79 0.42
Tergo™ Metal Cleaning Fluid 0.42
Genesolv® 2004† 0.43
Novec® 71DA 0.45
Solstice® PF 0.45
Tergo™ High Perf. Flux Remover 0.45
n-Proply Bromide (nPB) 0.49
MicroCare HDS 0.57
Trichloroethylene (“TCE” or “Trike”) 0.58
Vertrel™ SFR 0.58
AK-225 0.59
Methanol* 0.60
Tergo™ CFCF Rinse 0.67
Vertrel™ XF 0.67
Freon™ TF† 0.70
Perc or PCE 0.88
Water 1.00
Ethanol* 1.20
Mercury 1.50
IPA Alcohol* 2.40

* Indicates a flammable cleaning fluid; this usually is an ingredient in an azeotropic blend.

† Indicates a Class 1 or Class 2 ozone-depleting solvent; no longer used by environmentally responsible companies and countries; included here merely for completeness.