This is especially true if the resin has high viscosity and short pot life. Air bubbles may then be reflected in a finished casting. 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. 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 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. Temperature will affect the viscosity of most materials. The higher the viscosity of a liquid, the thicker it is and the greater the resistance to flow.
If you are interested in learning more basics about viscosity, Check out our BACK TO BASICS series on Viscosity: Interested in getting more information on how a viscometer can assist with your work? Powered by VROC ® technology, RheoSense viscometers provide dynamic or absolute viscosity measurements that are absolutely reliable tools for your work! This is because absolute viscosity is given instead of values that compare fluids to one another. While relative viscosity can give you a general number, tools that can measure dynamic viscosity or aboslute viscosity have been refined and proven to provide more reliable and accurate measurements. Described above, viscosity measurements are often distinguished as either kinematic or dynamic viscosity. In general we can narrow down the options by analyzing their base principles. The number of methods and types of viscometers used to measure viscosity is rather quite large and the history of viscometry goes quite back.
If I fix the time I want to take for the injection (or the injection rate) and I measure the force or stress, this is what we will refer to as a measurement of dynamic viscosity. You might have also noticed that in this case I have been applying and measuring force to make the fluid flow. On the other hand, if you have honey inside the syringe, you better have a prety sturdy syringe and some mechanical system to help you apply enough force. You can probably push the fluid out using your fingers. Imagine that you have a very low viscosity fluid (water) inside a syringe. (Speaking of food, what's on the viscosity menu? Read more about food viscosity!)īack to the subject, another way to think about it is using a piston or syringe type of setup. In this example, the applied force is gravity. That's what we refer to as a measurement of kinematic viscosity or how fast does a fluid flow for a given force applied to it. You might have notice that I have been talking about time when trying to establish which of those two fluids is more viscous. On the other hand, a high viscosity fluid like honey would take minutes to pour out and the interface between honey and air would take just as long to settle. Water will pour out of a glass in a fraction of a second and will take the shape of the receiving container in just as short of a time. You can think in terms of different fluids taking different times to, for example, pour out of a cup. ( Watch our webinar on the different types of viscosity!) Viscosity can be measured using various methods from do-it-yourself methods to viscometers that are available in the market. Just like in the case of friction between moving solids, viscosity will determine the energy required to make a fluid flow. This can be also understood as friction between the molecules in the fluid. However, this definition can be confusing when we are looking at fluids with different densities.Īt a molecular level, viscosity is a result the interaction between the different molecules in a fluid. You can think of water (low viscosity) and honey (high viscosity). Viscosity is often referred to as the thickness of a fluid. Viscosity is defined as the resistance to flow!