Tips & Tricks For Managing Screen Printing Ink Inventory

Learn how to get the maximum money's worth out of your inks and to set up a system that allows you to locate and replace inks most efficiently.
Effective ink management may seem like a production issue, but it's really a management challenge. Maintaining the right amount of product, managing costs, and organizing inventory are all important issues for every shop owner or manager to handle - issues that could translate into higher profits, if handled properly.

Our shop has around 50 standard ink selections, 18 of which we use regularly for the majority of our jobs. While many shops keep a separate ink room away from the presses, putting the ink right by the presses is more efficient, as it minimizes the distance press operators have to walk to get ink. They pick the ink they need, put it on a wheeled cart, and roll it over to the press.

Part of our shelving system is made from 2" x 4" plywood, and the rest is made from pallet racking that we purchased from companies going out of business. The shelves don't match, but we're striving for functionality and cost efficiency, not beauty. Inks are housed on the shelves starting off with lower PMS numbers (032, for instance) and working their way around to 9999. This way, employees can walk by the shelves and find what they're looking for with just a quick scan.

We keep primary colors in three sections of shelving; all the bases, modifiers, tools, pylon, etc., are in another area of shelving. Next to that is an 8-foot area, where we do all of the ink "cooking," if you will. Formula sheets are stored in a three-ring binder, as the area is too messy to keep a computer for ink mixing. Production employees can use either the computer in the receiving or shipping area-both of which are in the production area. They simply call up the software, print off the formula, and add it to the three-ring binder.

Mixing It Up
Every time we mix a color, we store it in this formula book. When the production staff sees an ink number that they're not familiar with, they can leaf through the book, find the ink number, and see the formulation. They can look on the 48-foot shelving we have that contains about 100 custom mixes. If there's leftover custom ink from the previous job, they'll use it; if not, they'll mix more and store it on that 48-foot shelf afterwards.

We mix a minimum of 1,000 grams at a time using 32-ounce cups, which are big enough that it's easy to mix without making a mess. We also use empty gallon buckets. (Note: We don't purchase gallon buckets; these are used, emptied ink buckets that we clean and recycle.) Next, they use a permanent marker to label the container with the PMS designation number, and whether it's a C (coated) or UC (uncoated). Sometimes the difference between coated and uncoated Pantone colors is significant.
Throughout the course of the day, the production manager may have as many as 30-100 orders laid out in sequence for that shift's jobs. He'll need to sift through the jobs and see which inks need to be mixed, and when that should occur. We try to have the ink prepared two hours prior to the job's start time. We don't want to fire up the presses only to discover that ink isn't ready, or that there isn't enough of it, so this two-hour window gives us plenty of room to avoid that problem.

The amount of ink you should mix depends on the likelihood that you'll use it again. If there's a strong likelihood of using it again for that customer or others, you may mix a gallon. However, our shop never mixes less than 1,000 grams, which is the minimum for getting consistent coverage on an automatic press. Again, the key is to make sure you mixed enough to cover the job, because it's costly and inefficient to stop the presses and mix more.
Ink mixing software can help minimize waste by developing formulas that reclaim ink leftover from other jobs. You might have 1800 grams of a particular custom mix of green left from a job, and by adding a calculated amount of other mixing components; you'll get the required color. This cuts down waste and keeps your ink shelves from getting completely overloaded with leftovers.

Keeping it Organized
Periodically, we'll take a look at our ink inventory and realize it's time to reorganize things. About once a year, we adjust the spacing to keep everything balanced and easy to find. We also use this opportunity to remove ink blobs and messes on the shelves.

Of course, screen printing is a messy business, and that's not going to change. That said, it's still a good idea to wipe down the shelves, even if you're not going to be eating off them, or things will not get so messy they become intolerable.

As far as grouping inks, you could organize them by AP ink, MP, and specialty ink. Or, you may want to organize them in terms of frequency of usage. The key is to develop an organization system that everyone understands, and then stick to it. It's a waste of time and money to have employees walking back and forth in front of the shelving trying in vain to find a particular color.

Our ink shelving stacks so high that we use a long stepladder, called a stock picker, to reach items at or near the top. We keep those inks used less frequently near the top, while the 18 we used most often are at or near eye level.

Throwing It All Away

Ink management doesn't end when the job is over.

We live in an increasingly eco-friendly, eco-conscious world. Certainly no one would dispute this is a good thing-one that will help keep our planet, its resources and its inhabitants safer for generations to come. However, there are some practical tradeoffs, not the least of which is figuring out what to do with materials that may be perceived as hazardous - even if they're really not a big deal.

Plastisol ink is one such material. I'm no chemist or Environmental Protection Agency employee, but my understanding is that you could literally eat plastisol ink and it wouldn't cause you much trouble, aside from a little intestinal distress. Still, even though ink is relatively benign, the environmentally responsible thing to do is to dispose of ink properly, not just toss it in a dumpster.

Although plastisol isn't flammable, it is leachable, so you need to lock it up, or make it "non-leachable," which you can do by curing it. Let's say you had a long run with a lot of flashing, and ink started to gel on the screen, so you scrape it into a sludge bucket. You could get rid of it by spreading it thinly on cardboard, running it down the dryer and curing the ink. Then you're generally safe to take the piece of cardboard and toss it the dumpster.

Of course, if you have a larger amount of ink, this would be a slow, impractical way to get rid of it. In these instances, you can use ink additives available from industry suppliers to cure the ink. For example, one supplier offers a powder that mixes with the ink to chemically cure it, turning it into a hardened, non-leachable material. In most areas of the country, it's acceptable to pitch this material into the dumpster.

What if you have even larger quantities of ink to dispose of - if you're going out of business, for instance? In this situation, you'll want to make contact with a waste disposal company, which will haul away the ink for up to several hundred dollars per drum. They usually dispose of the material via incineration or by incorporating it into something like asphalt or cement.

As with most things that aren't much fun to do, ink disposal can be put off week after week, leaving you with a big mess to handle. Keep things under control by getting rid of excess ink fairly regularly-when the ink is, in fact, waste. You don't want to throw away dollars inadvertently, and in many cases, you can scrape ink back into the buckets for later use.
One exception: Yellow process ink is something that we rarely put back into the bucket. That's because we print on a screen with a blue dyed emulsion, so the yellow leaches blue dye from it, giving the ink a green cast. There's no point in saving color-shifted ink, so it goes right into the sludge bucket.

Written By: Greg Kitson
U.S. Screen Print & Inkjet Technology