Cork Tech Talk Blog

A surface that is easy to wet is necessary when printing and coating in order to achieve good adhesion and appearance results. “Wetting” is the ability of a liquid to spread, contacting a solid surface. All liquids have a surface tension and all solids have a surface energy. Both are measured as a force applied over an area, expressed as a dyne level. 

Read more: Adhesion Factors of Surface Energy & Surface Tension

Recycling and Sustainability in UV and EB Cured Packaging

Paper and paper board products printed and coated with UV and EB curables are recyclable. They have always been recyclable into lower grades of paper known as “greyback” or “fillerboards.” These grades include materials used to produce folding cartons, corrugated, wallboard, tissue paper, roofing paper, and cellulose insulation. This category of recycling into lower grades of paper is known as “downcycling.”

Read more: Recycling and Sustainability in UV and EB Cured Packaging

Aqueous coatings formulated for the graphic arts industry may be thermoplastic or thermosetting, solution or emulsion polymer blends. Thermoplastic coatings dominate. They are comprised of approximately 60% water, plus property enhancing components including plasticizers, waxes, surfactants, coalescent aids, antifoams and possibly optical brighteners.

Read more: Storing and Handling Aqueous Coatings in Cold Temperatures

OFFSET PRESSROOM AIR EVACUATION, WHY?

The control of humidity is critical in offset printing in order to optimize productivity. It is well known that dry air causes paper to lose its moisture so that wrinkling, paper jams, and register issues are likely due to a pick-up in static electricity. A humidity level of 45 to 50% is recommended for paper storage, pre-press, and pressroom environments.

Read more: Using Humidity Control to Optimize Pressroom Productivity

How Foam is Formed

Foam consists of bubbles that are formed when air or a gas is trapped in a liquid or solid substance. Certain conditions are required for foam to be formed. Mechanical work or agitation is required, as are surfactants that reduce surface tension, so that work increases surface area. Also, foam must be formed faster than it breaks down. In most foams the volume of air or gas is large with a very thin film of liquid, or solid material enveloping the bubbles.

Read more: Foam can be a Problem in Coatings

The Success of Aqueous Coatings 

The use of aqueous coatings by the printing industry is, without doubt, a success story that now sees many millions of pounds of coating used annually to protect and enhance the printed material. This success has not always come easy, as the processes of printing involve many variables which must be in control in order to produce the desired, saleable result. These variables are inherent to the printing and coating processes themselves, and encompass such things as color shift, substrate, inks (pigments), coating, fountain solution, ink coverage, speed, drying, handling, shipping, and last but not least, the effects of the environment. 

Read more: Color Shift & Aqueous Coatings

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About the Author

Elmer W. Griese Jr, having accumulated 35+ years of knowledge working in the coatings and printing ink industries has now authored the Cork Tech Talk News, newsletter since 1992 producing 112 issues. He remains dedicated to educating and illuminating technological progress that offers the potential to advance coating technology and its applications.

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