How to Convert Offset Ink to Black

Use rework or aged colors to make a dense vibrant line black.

Because ink represents a significant cost of offset printing, finding a way to use up partial cans of rubine red, violets, purples and blues can save you money. Before simply scrapping your aged or excess inventory, consider reworking those items into a vibrant, dense line black that will provide depth to your print and put dollars back in your pocket.

Things You'll Need

• Aged or excess ink inventory
• Neutral black ink base
• Ink knives and spatulas
• Uncoated draw down pad
• Small, medium-stiffness scraper
• Scale or industrial balance
• 3- or 5-gallon bucket
• Ink mixer or high-power hand drill with paddle bit used for mixing dry wall mud
• New empty 5 lb. ink can
• Labels
• Oil skins

Instructions

1. Identify your press returns and make sure you won't be using any of the inks for upcoming jobs. Use blues, violets and purples to create a dense rework black. You can use reds but in lesser amounts (20 percent or less). Ensure that you use only compatible ink types. If you are uncertain as to the compatibility of two inks, consult your ink supplier.

2. Obtain a finished neutral black base from your ink supplier. Take a small sample of the neutral black and the rework color or colors and create a mini-batch of rework on smooth flat surface such as piece of glass. carefully noting the amounts of each ingredient by weight (grams works well). Aim to get 20 to 25 percent of rework into the neutral black base (7.5 to 8 grams of neutral black to 2.5 or 2 grams of rework). Mix thoroughly.

3. Take a small dab of the mini-batch and apply the sample to the top of a piece of uncoated draw-down paper with a small ink knife. With the medium-stiffness scraper, evenly scrape the ink sample down the length of the paper. Tear off the sheet and hold it up to the light. If you see the mass-tone of the black change to brown or green, reformulate the mini-batch until you get the desired mass-tone and density.

4. Create a formula -- in pounds -- for making the larger batch. For example, if your mini-batch achieved the density you desire with 25 percent of rework in the batch, multiply the amount of ink you wish to end up with by 25 percent. If blending a 10-lb. batch multiply 10 by 0.25. Use 2.5 lb. of rework to 7.5 lbs of neutral black. Place the clean three- or five-gallon empty bucket on the scale or balance, and tare off the weight so that it equals zero. Transfer each ingredient into the empty container based on the amounts in your formula.

5. Mix at low speed with the post mixer or hand-held drill. Use only low speed to avoid incorporating air into the batch and causing a build-up of heat, which will change the physical characteristics of the ink. Stop mixing after five minutes, and scrape down the sides of the bucket with an ink spatula. Mix the batch for another minute or two.

6. Take a sample of the batch. With the small ink knife, dab a small amount on the top of the uncoated draw-down pad. Slowly and with even pressure draw the ink dab down the length of the pad or piece of paper with the medium-stiffness scraper. Compare this draw-down with the draw-down you created from the mini-batch. If it looks different, check your formula and math to ensure you figured correctly. Go back to Step 2 and create a larger batch by adding either more rework color or neutral black to achieve the desired density and mass-tone.

7. Choose the container in which to store the newly created black. You can elect to leave the dense black in the 3- or 5-lb. bucket or transfer into clean 5-lb. empty cans and label as Rework Dense Black. Include the ingredients and formula on the label. Place a new oil skin on top of the ink before sealing the can or bucket so that you can prevent the ink from skinning over.

Tips & Warnings

• Use only inks that have not already begun to cure or dry.

• A purple or blue mass-tone is what you are looking for to achieve really dense black on the finished print.

• Be sure to keep an accurate account of how much neutral black you used to rework color.

• Use Dense Rework Black only for line work or spot blacks.

• Do not mix conventional and energy-curable inks.

References

• Star Graphics Supplies: Frequently Asked Questions