In layman’s terms, viscosity defines a fluid’s resistance to flow. The higher the viscosity of a liquid, the thicker it is and the greater the resistance to flow. Temperature will affect the viscosity of most materials.
What does viscosity mean to you when selecting a mold rubber? If you are using a mold rubber with a high viscosity, there is a chance the rubber will cure with air bubbles that may then be reflected in a finished casting. If the mixed viscosity of the mold rubber you are using is higher than 15,000 cps, you may want to consider vacuum degassing the liquid mold rubber.
What does viscosity mean to you when selecting a casting resin? If you are using a casting resin with a high viscosity, there is a chance the casting will entrap air. Air bubbles may then be reflected in a finished casting. This is especially true if the resin has high viscosity and short pot life. If the mixed viscosity of the casting resin you are using is higher than 7,500 cps, you may want to consider vacuum degassing or pressure casting the resin.
EVERYDAY CONSUMABLE GOODS IN RELATION TO GENERAL PRODUCT VISCOSITY IN CENTIPOISE (CPS)
| Water @ 70°F / 21°C | 1 | centipoise (cps) |
| Blood or Kerosene | 10 | centipoise (cps) |
| Ethylene Glycol or Anti-Freeze | 15 | centipoise (cps) |
| Motor Oil (SAE 10) | 50 | centipoise (cps) |
| Corn Oil | 65 | centipoise (cps) |
| Unfilled Rigid Urethane Resin | 80 - 120 | centipoise (cps) |
| Maple Syrup or Motor Oil (SAE 30) | 150 - 200 | centipoise (cps) |
| Castor Oil or Motor Oil (SAE 40) | 250 - 500 | centipoise (cps) |
| Glycerin or Motor Oil (SAE 60) | 1,000 - 2,000 | centipoise (cps) |
| Pourable Urethane Rubbers | 1,000 - 3,000 | centipoise (cps) |
| Honey or Corn Syrup | 2,000 - 3,000 | centipoise (cps) |
| Molasses | 5,000 - 10,000 | centipoise (cps) |
| Chocolate Syrup | 10,000 - 25,000 | centipoise (cps) |
| Pourable Silicone Rubber | 14,000 - 40,000 | centipoise (cps) |
| Ketchup or Mustard | 50,000 - 70,000 | centipoise (cps) |
| Brushable Silicone Rubber | 100,000 - 150,000 | centipoise (cps) |
| Peanut Butter or Tomato Paste | 150,000 - 250,000 | centipoise (cps) |
| Brushable Urethane Rubber | 200,000 - 300,000 | centipoise (cps) |
| Lard or Crisco Shortening | 1,000,000 - 2,000,000 | centipoise (cps) |
| Caulking Compound | 5,000,000 - 10,000,000 | centipoise (cps) |
| Window Putty | 100,000,000 | centipoise (cps) |
These are general averages and NOT specifics, not all products fit neatly in this chart. Please check Technical Bulletins for specific mixed viscosity of products. Temperature will affect the viscosity of most materials, these estimated numbers are based on measurements at 73°F / 23°C
Click here to download a pdf of the Viscosity Scale Reference Guide.