Why Not to Use Brush Applicator Caps for Bottled Dyne Solutions

Question: Can you supply dyne fluids with brush-caps?

Answer: We do not feel that using brush-caps is an appropriate application method for surface tension test fluids. This packaging has gained some popularity because historically, these dyne solutions were often sold by treater manufacturers in this format. Unfortunately, this is fundamentally and theoretically about the worst possible way to apply the test fluids.

First, as the brush applicator is used to spread out the test fluid, it will pick up any surface additives or contaminants present on the surface of the sample. This could include surfactants, slip or anti-static agents, anti-blocking compounds, etc. Worse yet, if testing metal for cleanliness, the residual oil on the sample’s surface will be absorbed into the dyne solution, and the brush’s fibers. These contaminants will then be re-introduced into the supposedly reagent grade dyne solution when the bottle is re-capped. This will permanently alter the test fluid, making it essentially useless.

Second, brush applicators apply far too much test fluid. As surface energy is a two-dimensional attribute, you need to use as thin a film of test fluid as is possible. An excessively thick application of test fluid will affect results, as gravitational spreading will become a factor at the liquid—solid interface.

In summary, using brush-caps as applicators for dyne solutions is simply not a good idea at all!

Published by

Russ Smith

Russ Smith formed Diversified Enterprises - the first business to focus specifically on applications of the dyne test - in 1986, and has served as President of the company ever since. He has over 30 years of experience in the fields of surface treatment and analysis, and deals with technical inquiries from customers worldwide on a daily basis. Russ is a member of ASTM, the Society of Plastics Engineers, the American Chemical Society, the American Society for Quality, the American Association for the Advancement of Science, and TAPPI.

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