It's a simple test for your offset printing ink that any pressman can do with limited tools. It will tell you how compatible your ink and fountain solution are. It will also tell you why you may have scumming problems - or more correctly tinting or toning problems. It is a test that the chemists at major ink companies such as Sun Chemical or Flint will do and if you would like to speak intelligently with them, they will know this test. Quite simply, it will help you troubleshoot your ink.
The Ink Bleed Test
The only things you need to perform this test are shown in the picture above. Here is what you need:
- A small sample of the ink you are currently running.
- About half a cup of your mixed water and fountain solution.
- An empty plastic bottle.
To perform this test, do the following:
- Cut out the bottom of a plastic bottle (about the bottom 2 inches)
- Put a small dab of ink in the center of the ink you want to test.
- Put your current running fountain solution and water mix into the cup so that it is about the same height as the ink.
- Time how long it takes before the ink bleeds into the water.
Notice the very light colored pigment that is bleeding into the water. This only took about two minutes. The reason is because we used distilled water in this instance. GATF recommends using distilled water as it is much more aggressive. So what counts when you use distilled water is how many minutes it takes to break down the ink as it is in the picture above.
What It Tells You
What appears to be a scumming problem, may actually be tinting. In other words the water may be breaking down your ink and you are constantly fighting what appears to be an ink and water balance problem. When troubleshooting a problem like this, it is good to perform this test. If you follow these steps, you can communicate intelligently with your ink supplier. At the very least, your water and fountain solution mix should not break down your ink as it does in the above picture. If it does, call your supplier. He will likely want to do his own testing which may not amount to much more than what you have already done.
Give it a try. Leave me a note and let me know what you find. If you think this test is useful, recommend it or "Like" it on Facebook. It's a great little troubleshooting tool for any pressman.
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