Pick-Outs and Coating Lumps
Sounds kinda gross to me, like something you would find in your nose after a bout with a bad cold. In printing lumps and pick-outs can develop from paper surfaces. As each sheet of paper travels through the printing press a tremendous amount of pressure is applied. This can cause the paper surface to breakdown depending on the grade of paper. Use this article to help guide you through your printing blunder analysis.
How Coating Lumps Form
1. Coating lump being pulled from the surface of the paper.
Lumps come from paper coating or adhered to the paper's surface
2. Original
3. 3rd sheet after original.
4. 6th sheet after original.
Pick-Outs and Coating Lumps are agglomerates of fiber or coating material that are bound into the paper coating or adhered to the paper’s surface. The tack of the ink, or inks, will lift the defect from the paper’s surface (Figure 1), and sometimes does not fracture the coating. The white non-print speck on the original sheet appears on the unit where the lump lifts off, and the paper’s surface below then becomes printed with the subsequent colors. Eventually this lump of coating picks up ink and prints from blanket. The three prints above show the original sheet and the 3rd and 6th sheet after. (Figures 2,3, and 4)
Coating lump from the blanket
5. Coating lump visible through a loupe on the white paper before printing.
6. Tape pull of the coating lump from the blanket.
7. Photomicrograph photo at high magnification of the coating lump.
8. Chemical analysis of paper coating materials.
This type of Pick-Out can vary in size from 1/32″ in diameter to the size of a quarter (which can result in a smashed blanket). White paper samples should be obtained for close examination. Some lumps can be seen on the white paper sheets before printing. (Figure 5)
Tape Pulls (Figure 6) from the blanket can be photographed and analyzed to confirm their origin. Even under the low magnification of a loupe, this material appears as a lump of white coating which has been printed.
Further analysis on an S.E.M. at high magnification will confirm the presence of coating materials (Figure 7). Note that there are no fibers in these lumps (see page lOon Coating Pick and page 12 on Wood Vessel Segments).
The corresponding chemical analysis
(Figure eight) indicates the presence of Al and Si (Aluminum + Silicon = clay), Ca (Calcium = Calcium carbonate) and Ti (Titanium Dioxide).
Finding a printer for your small business is necessary if you want effective direct mail results, and they are not very easy to find. Talk to your business friends to find more options for your printer of choice. Once you find out that you have a commercial printer on your side you should be good to go.
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