Coatings Clinic

Last Words on Cratering

a colorful abstract image of paint on concrete
Editors’ Note: On the occasion of this final Coatings Clinic column, ACA and the editors thank Cliff Schoff for his innumerable contributions to this publication and the profession. We appreciate his willingness to share his insights and industry expertise.

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Additives: More Art than Science

Liquid poured from beaker
Additives modify paint or film properties or behavior, preferably (but not always) improving them. They are critical to successful formulation and to solving all kinds of paint problems, but choosing the right one can be exceedingly difficult and usually involves extensive trial and error.

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Coatings Clinic: Thoughts on Formulating, Part 2

Blue silkscreen ink
This is a continuation of the article begun in the September 2020 issue of CoatingsTech. Part 1 ended with film formation but had not discussed paint flow, which occurs during making of the paint, its application, and through film formation. The formulation undergoes a wide range of shear stresses on pigment dispersion, mixing, storage, application, and post-application. It responds to...

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Thoughts on Formulating, Part 1

Industrial mixer mixes paint with water emulsion in a bucket
I have never been a formulator, but I have worked with formulators for nearly 50 years and learned a lot from them. In this article and the one that will follow, I will set out what I think are the things that need to be understood to formulate superior coatings. Readers may say that much here is obvious, but I...

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Pigment Dispersion II, Testing

Ink in water isolated on white background. Rainbow of colors
Pigment dispersion quality in pastes and paints may be tested by one of several different techniques. Probably the most common method in labs and plants is taking readings with a grind gauge, usually the Hegman type (ASTM D1210). The main reason for doing this for pastes usually is to see whether the dispersion process has reached the required end point...

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Pigment Dispersion I, The Basics

Several bright colors of dry holi paint
A friend recently wanted to know about pigment grinding, which made me realize that I had better begin this article by saying that we do not grind pigments, we disperse them. A bag of pigment contains clumps that must be separated into smaller clumps or individual particles. This is necessary in order to produce paint that provides good appearance on...

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Coatings and Radiation

Coatings and Radiation
In June/July of 2019, I was irradiated with Bremsstrahlung X-rays to knock out prostate cancer. The radiation did its job, and the cancer appears to be gone. Being fair-skinned, I also have experienced skin cancer. My experiences have made me think about radiation effects on coatings for good or ill, as well as on me. We use UV and IR...

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Problem Solving—Again

high powered microscopes
I have published many of the thoughts and recommendations in this article previously in CoatingsTech. However, since paint problems continue to occur and there may be new readers facing them, I thought that this was a good time to discuss problem solving yet again. Surface defects probably are the most common type of paint problem, but it is not always clear...

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Weathering and Field Defects

mpty blue wooden background, texture with copy space
The coating system almost always is blamed for field defects, but there are other possibilities: design of the painted object, poor substrate quality or surface preparation, and the process, including application and cure. Was the painting done in the sun? Or in the rain? Were the freshly painted rail cars pushed out into fog? Were all the required coats applied?...

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Sustainability and Pigment Dispersion

vernice acrilica con margherita
It may seem strange to link sustainability with pigment dispersion, but an important strategy for improving coatings sustainability is to make higher quality coatings that last longer and to make them more efficiently. Increasing the effectiveness of pigment dispersion saves time and money, improves appearance, reduces the frequency of surface defects, cuts down on pigment usage, and is likely to...

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