In lithography, the difference between offset sheetfed ink construction and offset web heatset ink construction lies in the specific requirements and properties of each printing method.
Offset Sheetfed Ink Construction:
1. Sheetfed Printing: Sheetfed offset printing refers to the process where individual sheets of paper are fed into the printing press for printing.
2. Ink Characteristics: Sheetfed inks are designed to be used on a wide range of paper stocks and substrates, including coated and uncoated papers. These inks have a medium viscosity to ensure smooth flow and excellent print quality on various paper surfaces.
3. Drying Process: Sheetfed inks rely on absorption and oxidation for drying. Once printed, the sheets are typically stacked and left to air dry or passed through drying units in the press.
Offset Web Heatset Ink Construction:
1. Web Printing: Heatset offset printing is primarily used in high-speed, continuous roll-to-sheet or folder printing processes where the paper is fed from a large roll.
2. Ink Characteristics: Web heatset inks are formulated to be used on lightweight, heat-resistant coated papers typically used in magazines, catalogs, and high-volume printing. These inks have a higher viscosity to prevent excessive ink setting during the high-speed printing process.
3. Drying Process: Web heatset inks utilize a combination of heat and forced air to rapidly dry the ink as it passes through drying ovens. This allows for quick drying even at high printing speeds.
The price difference between offset sheetfed ink construction and offset web heatset ink construction can be attributed to various factors, including:
Sheetfed inks are comprised of Natural Renewable resins, mostly, vegetable oils and are generally a higher pigmentation loading to produce a thinner ink film to achieve optimum color density. These colorants are designed to match to ISO Printing standards that allow for SWOP or G7 color specifications. Sheetfed inks also contain expensive drying catalysts and other modifiers to provide ample slip and rub resistance. Sheetfed inks are used primarily in commercial paper printing and packaging/folding cartons that require a greater durability and higher quality printing.
Offset web heatset inks are comprised of mostly lower cost hydrocarbon resins and solvents. Since the drying mechanism for web heat set inks require the solvent to be evaporated in the printing process this is why they use these highly evaporative solvents in the ink construction. We use similar process color pigmentation to equal the color shades of the sheetfed inks. Web heatset inks do not require as much pigmentation (the more expensive part of an ink formulation) to achieve the proper ink film thickness and corresponding color density as compared to the sheetfed ink. The cost of the hydrocarbon materials is a little more stable than the renewable resources (natural resins and vegetable oils) in the sheetfed inks. This fact helps keep the price of Web heatset inks less compared to Sheetfed inks.
It’s important to note that the price difference can vary depending on the specific printing job, the complexity of the design, the ink coverage, and other factors. It’s always advisable to consult with printing professionals or service providers for accurate price estimates based on your specific requirements.
Peter Notti Technical Director Oil Based Offset Inks