Digital Dish: July 2019

By: Rick Williams

Jul 31, 2019

Each dish features a new nugget to chew on and fuel your digital cravings. This month's edition discusses HP® Indigo digital printing. This dish feeds you with education on how the 3-star rating system works and the evaluation criteria is determined, and also provides tips to guide you in selecting the optimal star-rated paper for your next print job.


1. HP Indigo Star Rating System

HP Indigo has established a simple 3-star rating system to determine how well individual digital substrates (both treated and untreated) perform on the Indigo press. A substrate is first tested at the Rochester Institute of Technology (RIT) to certify how well the Indigo liquid ink adheres, which is very important in Indigo printing, since the ink is polymer-based, it has a tendency to bind poorly into paper fibers without some sort of treatment either added to the surface or incorporated into the sheet itself. Accent® Opaque has been rigorously tested at RIT and maintains a premium portfolio ofIndigo treated papers with both 3- and 2-star rated certifications.


2. Star Evaluation Criteria

To determine what star certification a substrate receives depends on how well it performs in the following 3 categories: runnability, compatibility and ink fixing (aka adhesion). 

3-Star (Best): Liquid ink adhesion is 90% or greater, uses few print cleaners, and causes no paper jams and low scuff in converting processes.

2-Star (Better): Liquid ink adhesion is 80-89%, uses some cleaner sheets, causes 1 or more paper jams, and experiences some scuffing in post converting applications.

1-Star (Good): Liquid ink adhesion is <79%, uses the most cleaner sheets, and experiences scuffing in post-production. 1-star products must be left sitting for an extended period of time to dissipate the oils from the polymer; therefore, we don't see many in the market. Treated papers help prevent this issue.


3. Star-Rated Paper Selection

The higher the number of stars, the better an individual substrate performs, which is important to keep in mind when reviewing your upcoming print job. If the job requires photo-quality (and heavy ink coverage), we recommend using a 3-star certified treatedsheet like Accent Opaque, which is 99%+ on liquid ink adhesion. For jobs that demand less ink and post-print needs, a 2-star certified treated product should suffice, but you should always test prints through the press and post-converting processes to ensure it satisfies you and your customer's needs. We highly recommend using certified treated sheets on your Indigo press vs. non-certified untreated product, as untreated product can increase the risk of jams, poor ink-adhesion and reduced blanket life.


Request a Special DYK Offer

Did You Know that you can sign up to receive a monthly subscription of our DYKseries highlighting relevant trends and technologies in the print industry delivered right to your doorstep? Sign up today and, as a bonus, receive a complementary DYK with a complete list of Accent papers certified for HP Indigo presses. Reserve your copy today!


Want to receive the Digital Dish in your email at the beginning of each month? Sign up here.

If you have a topic you are hungry to learn more about, please email us at!