Among the most stubborn challenges flexo press operators face, reproducing color, run after run, has to rank close to the top. It seems as though somehow, even when we use the same ink color formula, or even the very same ink that was left over from a previous run, a given color doesn’t always match from run to run. Very often, ink color has to be adjusted at the expense of press time. That’s not good.
If you face similar challenges, I’d like for you to consider some procedures and ink formula naming methods that, adhered to strictly, will enable you to more consistently blend ink, with fewer color adjustments needed to subsequent batches, after a few press runs. You will have less downtime and waste resulting from color adjustments, you will create less surplus ink, and you will even be able to reduce your base ink inventory. You will need to be diligent about documenting ink base quantities used to create formulas as well as several other variables involved in the production of color. You may even need to develop a few new habits. However, I can promise that the effort will be well worth it.
The process of matching ink color involves weighing and blending ink bases, making ink draw downs with a hand proofer, printing the color at press, making color adjustments, and comparing color either by eye or color measuring instruments at various steps in the process. Each of the steps involved have their own set of procedures, and those procedures can vary from shop to shop, as can the instruments used. However, the procedures we discuss here can be adapted to any flexo shop. If the specifics of the procedures described here differ from yours, you should be able to adapt them to your particular situation.
To demonstrate the concepts, I’d like for us to imagine a scenario where we will print a simple two-color job. I choose two colors because I want for us to look at a custom ink name as well as an industry color standard name in the same example. We’ll use Pantone® as our standard for one of the colors, but if you use another standard in your plant, you can just substitute anywhere I use the term “Pantone®”.
I am also going to address an area that seems to create a lot of conflict in many pressrooms; calling a color a Pantone® (or other standard) color, when it is not! It’s a personal pet peeve, but I really have seen it create a lot of unnecessary confusion in color communication. We’ll build that into the scenario we create.
I’ll be covering the process from the time that the customer specifies colors that we don’t yet have formulas for, through the steps that it takes to match the color at press, through matching the color on a second run, where variables affecting color differ between the first and second printing, and lastly through a third printing, where we will finally benefit from the work we’ll do to get there. I’ll outline what may be a familiar scenario here, and I’ll follow it with a more detailed and productive scenario afterwards:
- The customer communicates the colors desired.
- You blend ink bases and match the colors away from the press, ahead of time, using a hand-held ink drawdown device to save press time.
- Based on the weight of each of the base colors in the blends you make, you calculate the formulas of each color.
- You send the ink to the press.
- The printed colors are slightly off.
- You make one or more adjustments to shade and/or strength of each color at press. (This occurs because the hand-held drawdown device does not mimic press conditions precisely.)
- You match the colors at press and you print the job.
- At the end of the job, you store the surplus ink for re-use.
- Some time in the future, your customer requests more of the same printed item.
- This time, you use the same ink that was left over from the previous run, and it’s in perfect condition. However, one or more one of the following variables affecting color has changed:
You start printing and the colors you generate, using the same ink you used previously, are slightly off-shade requiring you to make adjustments to the color at press.
- The press
- The anilox geometry
- The specific anilox, even if the geometry is the same as before
- The substrate
- Overprint coating has been added, omitted, or modified
You match the colors again and start printing.
Because it’s a long job, additional quantities of ink become necessary.
You blend more according to the formulas you calculated the first time you ran the job, guessing at the additional amounts of base colors you added at the press.
You add it to your press’ ink system and discover that the color is slightly off shade!
You shake your head, grit your teeth…
You match color.
You print the job a third time.
The colors don’t match!
If this sounds familiar, you are not alone. This scenario is common to most of the pressrooms I’ve been in. Fortunately, very little needs to be added or changed to the process outlined above to close some of the gaps and greatly improve your ink blending success. Now, let’s go into greater depth, making some stops along the way to discuss some of the critical points I’d like for you to consider.
The customer communicates the color(s) desired
There is more than one way that your customer can communicate a color. They may provide you with a sample that your competition is printing for them. They may refer to a color in a standard guide, such as a Pantone® color book. They may refer to a color on a business card, letterhead, or article of clothing. They may even provide numerical data from a colorimeter or spectrophotometer. Regardless of the method, you should have something to go by so you know exactly what each color should look like when printed. Whether it’s a sample, guide book, or numerical data, we will refer each of the colors we are to match to as the Printed Color Standard for that color. It is the standard against which you will compare the printed color.
For each color we develop, we will create at least two standards: The Printed Color Standard described above and the Drawdown Color Standard. I will discuss the drawdown standard a little later.
The Printed Color Standard, or PCS, will assume the name given to it by the customer. The Drawdown Color Standard, or DCS, will assume the longer ink formula name that will aid in the management of ink color blending and matching. In our two-color example, the customer calls the colors “ABC Blue” and “Pantone® 185 Red”. The blue is a custom color name, so we will automatically include “ABC Blue” within the formula name of the ink blend we develop for this color on this job. The Pantone 185 Red is a well known and recognized color. It looks like we will be using “185 Red” within the formula name of the second blend.
However, when the sample makes it to the press with the work order, the operator compares the color of the sample to his current Pantone® color guide, and notices that the red on the sample is not a good match against the color standard in his color book. IT IS TIME TO ADDRESS THIS RIGHT NOW! If it is not an exact match to a Pantone® color, or any other standard color, you must contact your supervisor, customer service, or the customer and clear the matter up. In my opinion, there are only two choices: 1) The customer (authority) agrees that you will create a custom color name (ABC Red, perhaps) and that you will match the sample provided, or 2) the customer agrees that you will match to the standard color guide.
If you decide to disregard the matter and match the sample while still calling it Pantone® 185 Red, you and/or the customer will run into all sorts of color matching and consistency problems down the road. It is critical to be clear on this first step.
Fortunately in our scenario, the customer suspects that the shop that printed the sample did not match the color the way he should have, and confirms that his plastic bag and folding carton printer also are matching to Pantone® 185 Red for his logo. Therefore, we will indeed be using 185 Red within the name of the blend we create for the red.
Match the color away from the press, ahead of time
Ink should be blended to color ahead of time, away from press, whenever possible. Adjusting color at press is bad enough. Creating a new ink formula from scratch at the press is worse. That said, in the lab, or away from the press, it is not feasible to predict and drawdown the exact same film thickness that will be generated by the press. There are simply too many variables involved to mimic press conditions, no matter how expansive your inventory of hand-held anilox rolls. Therefore, at this stage, you match the ink batch you are creating to the PCS, and hope that it comes close when finally on the press. You should have some idea of what to blend together for starters, but expect to make adjustments at press.
When blending, carefully record how much of each ingredient you add to create your first batch of ABC Blue and 185 Red. Record the quantities by weight, keeping track of each addition so that you can total each base weight once you’re satisfied with the colors. Whether you work with ounces, pounds, grams, or kilograms is not important, as long as you are consistent with the weight units throughout your calculations.
From the base weights, calculate the formulas for the blends. These will be the initial formulas for these colors. (For an explanation of calculating ink blend ratios, see “Reduce Your Surplus Ink Inventory”. For a handy calculator you can use to calculate ink blend formulas, click here.)
The batch of ink now goes to press
Remember that you will not be surprised if you need to adjust the colors at the press now. As I indicated earlier, the hand-held drawdown device does not mimic press conditions precisely. You ink your press up, and pull up color. You add a few ounces of reflex blue, an ounce of yellow, and a couple of pounds of extender to the ABC Blue, and make similar adjustments to the 185 Red.
The adjustments done, you make notes to the color formulas for the next time you blend the color. You will have to edit the formulas the next time you mix this color, but you don’t need to do it, yet. You will do this as you weigh out the bases again the next time you blend this color. For now, simply note the approximate amount of each ingredient you added to match the color and add comments to your formula notes.
Create Drawdown Standards for each color
This is, perhaps, the most significant part of the process. As soon as you are satisfied with the color match at press, take wet samples of the blue and the red ink from the press and make drawdowns with a hand-held drawdown device (proofer). These will be the Drawdown Color Standards, or DCS’s for these colors and they will become the standards you match to in the lab when blending subsequent batches of these formulas. They may differ in appearance from the press color standards, but they were created by the same inks that matched at press. This solves the problem of hand-proofers not mimicking press conditions, as now you will match a drawdown to a drawdown made with the same hand-held device.
It is important to document which device you use to drawdown the ink film. You’ll want to use the same device, or one that produces the same ink film thickness, each time you blend a given color. This is important, as different hand proofers with variations in ink film thickness can result in varying color densities. To make it easy to always know which device was used, you will incorporate its description within special nomenclature for your ink blends. I hinted at special names earlier, when I mentioned that we would use color name agreed to within the formula name we create. This is because the name will incorporate some of the variables involved in the production of color at press. Let’s look at that for a moment.
You will want to incorporate as many of the variables going into the production of your color as possible. I like to incorporate color name, press ID, press anilox ID and geometry, hand-held anilox ID and geometry, and substrate type. In our example, the blend names will be:
- ABC Blue,123,SN789,800,2.3,360,5.0,C1S
- P185 Red,123,SN542,600,3.0,360,5.0,C1S
- ABC Blue = Custom color name
- 123 = Press number or ID
- SN789 = Anilox ID or Serial Number
- 800 = Anilox line count, Press
- 2.3 = Anilox volume (BCM), Press
- 360 = Anilox Line-count, Hand-proofer
- 5.0 = Anilox Volume, Hand-proofer
- C1S = “Coated 1 Side” substrate
- P185 Red = Pantone® 185 Red
- 123 = Press number or ID
- SN542 = Anilox ID or Serial Number
- 600 = Anilox line count, Press
- 3.0 = Anilox volume (BCM), Press
- 360 = Anilox Line-count, Hand-proofer
- 5.0 = ox Volume, Hand-proofer
- C1S = “Coated 1 Side” substrate
The names above look cumbersome, but they serve a valuable function in accurate color reproduction through these methods. They communicate important variables that influence color to the press operator and ink blender. These folks will have some idea of what to expect, should there be a change in any of the variables.
For example, if one of the press-related variables above changes the next time you print this color, you will likely need to modify your formula to achieve correct color. By comparing the current variables to the previous ones, you can often predict the direction of color change. Additionally, by creating a new color formula name that incorporates the new variables, you will have two formulas for this color, one for each set of variables. If you again print with a different set of variables, create yet another formula name. Each unique set of press variables requires a new formula name, even though the final printed color is always the same. Ultimately, you end up with formulas for most of the configurations you are likely to use to print the color. Depending on the number of presses, aniloxes, etc. that you have available to print a given job, this can mean a great deal of scheduling flexibility and reduced downtime, because you have an arsenal of formulas to choose from that can suit more than one set of conditions.
Also, the cumbersome blend names are the formula names, not the color names. The PCS names remain brief, and all communication with the customer or anyone else will use the PCS names only, and there is only one PCS for any given color. The blend or formula names are for the person blending the ink, and the press operator, and aren’t used in conversation. They are used to correlate ink formulas to specific sets of press variables.
Print the job a second time
Because you had ink left over from the first run, this is the ink we start off with. This time, however, the anilox roll you used to print the blue color the first time is not available. You select a similar one from inventory, but the volume is a little higher. Therefore, you have to adjust the blue color a little by adding some extender. Again, a wet sample is drawn down, with a new formula name that reflects the different anilox roll used this time. You now have two formulas and drawdown standards for ABC Blue printed with two sets of conditions. That’s good. (Note: You still have only one Press Standard for ABC Blue.)
Print the job a third time
This is where you will first start to reap the benefits of these procedures. When you print the job the third time, it just so happens that the anilox roll you used to print ABC Blue the first time is available, and the one you used the second time isn’t. You inform the person who blends the ink for you and they produce a batch of ABC Blue, matching it to the DCS created the first time. Notes from the first time the job ran show what was added to the initial batch at press. The ink technician is not surprised that it took a slightly different formula to match the DCS, and edits the formula based on the new weights. You put it in the press, and it matches the PCS well. That’s good.
In summary, for every color formula you create, you want to end up with at least two standards:
- Printed Color Standard, or PCS: The standard you match the printed product to, every time. Brief name, such as “ABC Blue”.
- Drawdown Color Standard, or DCS: The standard you match to when blending all but the initial blend of an ink color. Long, informative name, such as “ABC Blue,123,SN789,800,2.3,360,5.0,C1S”.
Each time a different set of variables is used to print a color, a new DCS is created.
Only one PCS is maintained for a given color.
Adjustments to color at press or in the lab should be communicated between press operator and ink technician.
Precision at every step of the procedures above cannot be overemphasized.
Ink bases should be carefully weighed.
Drawdowns should be smooth.
Variables should be diligently documented.
Calculations should be double checked.
The minimum requirements for implementing the above procedures are:
- A place to keep formulas, such as:
Index file, log book, spreadsheet, or batching software
- A place to keep standards, such as:
Folders, binders, job history documents, colorimeter/spectrophotometer database
- Hand proofer or similar device for drawing down ink
- Discipline and perseverance!
Some of you may have noticed that I didn’t go over ink bases as variables. Sometimes you may have to blend ink using bases from different manufacturers than called for in a formula. Sometimes our base strengths vary from batch to batch. It can be an aggravation. However, as long as we match to drawdown standards in the lab, even these challenges are minimized. If you find that your matching process is perfectly executed, that you are in control of your variables other than ink base strength, and that you are constantly making changes to your formulas, I encourage you to agree to a quality standard with your ink vendor and possibly make incoming quality checks on your base colors. Explain to your vendor what you are doing, so that they can appreciate the need for consistency.
Ink management can be addictive, especially when you start to see results. Additionally, the discipline required to execute these procedures effectively develops other good habits with respect to ink inventory management, documentation, and order. The above procedures coupled with an effective ink work-off program and can go a long way in reducing many of the frustrations associated with reproducing color in the flexo pressroom, and you already have everything you need to implement them. Add a little luck, hard work, and persistence and you can dramatically reduce downtime and other waste associated with color reproduction in the flexo pressroom. That is very good!