Flow Rate
It is also important to note that each fluid or dye has its own minimum flow rate. The minimum flow rate is the smallest amount of dye at a given moment to keep the curtain flowing continuously. The minimum flow rate is directly proportional to the surface tension while viscosity is inversely proportional.
Curtain Coating is a pre-metered coating method, which means that the exact amount of coating needed to coat the substrate can be calculated before the process is actually accomplished. This is can be done by using the ratio of the flow rate (with respect to volume) and width of the substrate to the speed at which the substrate passes under the "curtain" of coating fluid.
Because of the ability to calculate the exact (or nearly so) amount of fluid needed for a given project, film thickness variations on the finished product can be kept within +/- 0.5% of the target thickness .
Read more about this topic: Curtain Coating
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—Chinese proverb.
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—Samuel Butler (1835–1902)