Conventional offset inks cure or “dry” when printed to form a plastic film. All conventional offset inks contain drying oils. Sometimes the drying oils may include petroleum oil. However, you don’t need petroleum oils to work (petroleum oils just make the ink work better in certain situations). Drying oils come from many  VEGETABLE sources; linseed oil, castor oil, tung oil, sunflower oil, safflower oil, rapeseed oil, soy oil etc. These oils have varying degrees of performance and suitability in printing inks.

 Prior to the 1960’s, most of the oil in sheet-fed inks was vegetable oil. Petroleum oils were introduced as press designs changed to facilitate faster  ink setting. This allowed jobs to print better and to be handled faster.  The primary thrust into printing for soy based inks was the news-ink market. News inks had been based largely on petroleum oils which were the most cost effective method for manufacture.  Because news inks don’t cure like sheetfed inks, they don’t need drying oils. Soy oil in news ink also offered a number of benefits over petroleum based oils; including better transfer, better color clarity and less rub off onto the hands of readers.

The Soybean Marketing Association then went into the sheet-fed offset printing ink market. But compared to linseed oil and tung oil, soy oil doesn’t dry as well. The association finally realized this and reduced the amount of soy oil required to meet their criteria for being “soy based”.  Remember, all drying oils are vegetable oils. That means all drying oils are a renewable resource. Being a renewable resource means these oils should be, unlike petroleum oils, a sustainable resource.

Soy oil, when properly formulated with other vegetable oils, is successfully used in sheet-fed inks everyday. We don’t have to surrender performance of our printing inks to achieve improved sustainability. The sustainability and performance combo is going to be more easily accomplished by allowing us to choose what drying oil combinations will work best rather than insisting on just soy inks.