Special viscometers and sensors are available that enable measurements up to about 100,000 s -1 comparable to airless spray and reverse roll coating. I have had many useful results with the old ICI cone/plate and the more recent Brookfield Cap 10 instruments to test ease of application. I highly recommend high shear cone/plate viscometers (ASTM D4287) that can apply a shear rate of 12,000 s -1 (10,000 s -1 where 50 Hz power is used). A conventional spindle-type rotational viscometer does not give shear rates much above 100 s -1, so it is not of use either. The Stormer instrument (see ASTM D562) often used to test architectural and maintenance paints operates at a low shear rate of about 60 s -1, which works well to test stirrability, but not sprayability or brushability. Reverse roll coating can give shear rates over 100,000 s -1, and the paint in direct roll coating probably sees shear rates of at least a few thousand s -1.Дifferent viscometers measure viscosity at different shear rate ranges. Brushing involves similar shear rates.ДЄirless spray has a higher range of 10,000 to perhaps a million s -1. air spray gives shear rates of 1,000 to 40,000 s -1.

Paint application is a high shear stress, high shear rate process. One reason for this is that rotational viscometers often display shear rate values as speed changes or it is easy to calculate shear rate from the viscometer speed. Although the key parameter affecting viscosity is the shear stress, people in the paint industry historically have looked at viscosity as a function of shear rate. This is called shear thinning, and the rate of deformation of the paint as it is sheared is called the shear rate (units are reciprocal seconds, s -1).

Shearing of paint breaks up its structure and the viscosity drops to a lower level (often much lower) than the paint had at rest. Direct roll coating is thought of as a low shear process (the application roller often just kisses the substrate), but the doctor blade and pre-application rollers may apply high shearing stresses. This also is true of reverse roll coating. With spraying and brushing, a high shearing stress is applied to the paint. Shearing can be envisaged in terms of placing a small amount of liquid in the palm of your hand and smearing it by passing your other hand over the first one. All aspects of paint flow, including stirring, pumping, transferring, sagging, and application involve shearing actions. However, that viscosity is not measured under just any set of conditions or done with just any viscometer. s) provides acceptable spraying, brushing, or roll coating.There is a rule of thumb in the paint industry that a viscosity of approximately 100 cps (1 P, 0.1 Pa I thought that I would extend my answer to other application methods and share the information. Desalination 59, 219вЂ“240.ДЇor kinematic viscosity Chen et al.I recently was asked about the optimum viscosity for spraying paint. Experimental methods for determination of the properties of saline water. Physical properties of seawater solutions. With the wide range of answers that you get from repeated lab measurement and/or using various equations, it is generally best to pick a single method and pretend that you believe it-repeatable results will not be available for viscosity measurements.Д«ased on Isdale, J.D., Spencer, C.M., Tudhope, J.S. None of the empirical methods provide results that match field conditions when there is any acid gas in a gas stream, and the equations of state methods are not a lot better for acid gases. The various methods can vary by more than 20% one from the next for the same fluid. It can also be predicted through an equation of state or one of many empirical relationships. One of the tubes is rotated and the amount of force that it takes to rotate at a fixed angular velocity is proportional to the dynamic viscosity. 4.1.1.1 Dynamic viscosity (Ој)Дynamic viscosity can be determined via an apparatus that has concentric tubes whose annular space can be filled with the fluid under test. Kinematic viscosity can be thought of as resistance to fluid momentum. Dynamic (or absolute) viscosity is an expression of a fluidвЂ™s ability to resist shear flows. Viscosity is a measure of the ability of a fluid to resist shear forces. Simpson P.E., in Practical Onshore Gas Field Engineering, 2017 4.1.1 Viscosity

Air viscosity