Tac: Total Area Coverage (of Printing Ink)

Your printer creates any number of different hues by overlapping halftone screens of each of the transparent process colors (cyan, magenta, yellow, and black) as each printing plate deposits these colors on the press sheet in successive order.

With his skill and training your printer can achieve this rather impressive feat and produce beautiful color photographs, solids, and gradations on your chosen press sheet. However, the paper substrate is absorbent (to a greater or lesser degree depending on whether it is an uncoated stock or a coated stock). Because of the porous nature of paper, it’s possible to print too much ink for the paper to handle.

Think about a newsprint press sheet, or an uncoated but higher quality press sheet, onto which a press lays down 40 percent, or perhaps more, coverage of ink to create a particular hue. If you do this for all process colors, the 40 percent multiplies fourfold, and you are now applying 160 percent total ink to the press sheet. Maybe this rises to 300 percent in other cases. Pretty soon you have an exceptionally wet press sheet that may not dry, or that may mark the successive press sheets as the wet ink offsets onto the paper it touches. Or at worst you have essentially a soaking piece of paper covered in ink.

With this image in mind, let’s discuss TAC (total area coverage). Gloss and dull coated papers will accept more ink because the ink will sit up on the surface of the paper. This overall percentage of ink coverage is called total area coverage. If you ask your printer, based on the kind of press sheet you’re using as well as the kind of press, he can give you a target percentage number not to exceed.

Let’s say this is 320 percent in a specific case. With this number in hand, you can create CMYK builds in Photoshop or InDesign for full-color images or background solids that can be comfortably printed without problems. Just don’t exceed that percentage. For instance, if you’re producing a rich black ink for a luxurious background, you want to make sure the percentages of cyan, magenta, yellow, and black when combined do not exceed that total percentage, the TAC or total area coverage for printing ink.

If you don’t adhere to these recommendations, here’s what can happen: ink won’t transfer properly in the printing process, pages can stick together, and ink can blister or pick off bits of the paper coating.

Online I found some target numbers that are industry averages, but ask your printer specifically for confirmation: 320 to 340 percent (out of a possible 400 percent for a printed area) for sheetfed offset printing on coated paper and 300 to 320 percent for heatset web printing.

Always Write It Down (Press Runs, Delivery Information...): An Object Lesson

Everyone makes mistakes. The goal is to catch as many of these as possible before they cause major heartache or expense. This is doubly true for a complex process like printing, in which multiple people participate and in which detail and precision are paramount.

In this context, I had two issues arise within the printing of a perfect-bound book recently. The first pertains to delivery information and the second pertains to contracts and press runs.

To make this a bit more concrete, the book in question is a 750-copy run of a perfect-bound book with French flaps. It is 5.5" x 8.5" and 88 pages plus covers. There are three delivery locations, and the second of the three just occurred today.

I have written about the publishers of these literary books before. They are a married couple with a small publishing house. Keep in mind that this book, and the prior one which differs only in the press run and the page count, have had an unusually long manufacturing schedule due to COVID-19 (closer to 8 or 10 weeks from proof approval, as opposed to prior schedules closer to 2 or 3 weeks), so it has been a challenge to keep track of their status.

The First Problem

My client sent me a book distribution manifest for the first title a number of months ago. I had sent the printer a delivery address list without actual book counts prior to that, and then I had followed up with the specific delivery totals once my client had finalized these numbers (close to the end of the job).

I had sent this revised delivery manifest to the printer but had apparently not made it clear enough that this was a revised copy of the delivery specs. Therefore, the printer’s packaging department had packed up and labeled the cartons based on the original delivery information, not the revised instructions in the email I had sent to the sales rep.

Unpacking and repacking cartons takes time. This time is not allowed for in the manufacturing process. So the printer at that point was stumped and not open to change without requiring more money and time. Plus delivery to my client’s destinations was firm. Missing delivery deadlines was not an option.

Fortunately, a solution was at hand. The cartons could leave the printer’s shop as they had been packed. My client’s book distributor would just break down a few of the boxes and resend these books to the second book distributor. The printer would need to do nothing.

What We Can Learn

This was, however, a learning opportunity. Here were my takeaways. I would encourage you to apply these to your own print buying work.

1. Wait until you have absolutely firm delivery information, even if your printer is pressing you for this information. It doesn’t help to provide the addresses now and the final counts later.

2. Put everything in writing, but also don’t rely on just an email. Make it clear in the email that these are the final delivery destinations. The same goes for all book manufacturing specs. If, however, as is sometimes the case, things change, make sure the email makes this revision clear in no uncertain terms. Personally, I would call the printer as well to note that the delivery information, or production specifications, have changed and to review this new documentation.

3. Don’t assume the email you wrote to the customer service rep has made it to the pressroom and book finishing department. This is why it’s good to call to follow up.

4. Do assume that during COVID-19 there will be staff shortages: fewer people doing more work at your printer’s plant. This is when errors occur.

5. Focus on finding solutions rather than blaming the vendor. Blame just inflames tempers and does not motivate the vendor to help resolve the problem. In my own case, my client was willing to have her book distributor repackage and forward a minimal number of books. This cost less than the book printer would have charged and avoided any delay. In your own case, be proactive and creative in this way.

The Second Problem

When it rains, it pours. When the second book was delivered to the book distributor, I forwarded the delivery manifest to my client. It was for one of three deliveries, and it was a smaller number of copies than she expected. My client was concerned about this delivery and the upcoming two other deliveries as well (the second book distributor and her own house copies). So I went to the printer with my client’s query.

I also went into my computer archives and looked for the signed contract for the book. What I actually found was two separate versions of the same contract: one with a 750-copy press run and one with a 1,000-copy press run. The press run had decreased in the course of a month. Fortunately I had both contracts, and both were dated.

So I sent both copies to the client, and she realized that she had forgotten the change in the press run (as I had; memory is imperfect). The printer had done as requested. My client was actually happy now with the result, since the smaller delivery total had been correct, not a 250-copy deficit. And I was happy because I had kept both contracts on hand. Even if I had forgotten the details, I had back-up written proof.

What We Can Learn

1. This is really very similar to the first problem. People have imperfect memories. My client had forgotten that she had reduced the press run. Having written, dated confirmation ensured that everything was as planned. In your own print-buying work, I would therefore encourage you to keep copious notes and signed documents showing all dates, costs, delivery addresses, and press runs.

2. When I initially approached the printer’s customer service rep to ask about the first delivery (requested at 850 copies but delivered as 650 copies, as per the delivery manifest), she noted that the order of delivery had been as follows: 50 to one book distributor, 100 to the publisher (my client), and the balance to the second distributor.

The concept of the “balance" is important because printers have a 10 percent overage/underage target for acceptable delivery. It is not always possible to hit a precise press run target due to all the separate operations within the book manufacturing process. Manufacturing activities, such as bindery work, damage copies, so it’s essential to produce more than needed to allow for spoilage.

That said, if the actual press run had been 1,000 copies, then receiving 200 fewer copies would have been too much “underage." As it was, since there was a second signed contract (at a later date), the overall total actually included 50 overage copies, which was in accord with printing trade customs.

As an aside, in your own print buying work you can often negotiate billable overage/underage percentages. Some of the printers I work with will agree to bill for 5 percent rather than 10 percent overs, for instance. If you need no fewer than a certain number of copies, however, your printer will need to increase the acceptable overage percentage quite a bit (like double the usual amount).

All of this is negotiable. Talk with your printer.

[Steven Waxman is a printing consultant. He teaches corporations how to save money buying printing, brokers printing services, and teaches prepress techniques. Steven has been in the printing industry for thirty-three years working as a writer, editor, print buyer, photographer, graphic designer, art director, and production manager.]