Discharge

Waterbased inks use water as the main solvent, and may also contain co-solvents and binders which can be petroleum based. The main purpose of these solvents are to carry the pigment, and control the cure rate of the ink film on the garment. Waterbased inks are used primarily on light colors, while discharge or HSA (high solids acrylic) inks are used for darks. Discharge inks are waterbased inks which contain a ZFS activator (zinc formaldehyde sulfate) of a certain percentage. This activator discharges the dye from cotton fibers, the pigment in the ink then replaces that dye with the pigment. The binder acts to bind the pigment into the garment.

Very bright and opaque colors can be achieved with waterbased and discharge inks, this in conjunction with the limited “hand” or feel of the print, makes this ink system very popular for garments that are sold in a retail setting. With discharge systems, Pantone color matching is often problematic and inconsistent. Due to the different dyes used by garment manufacturers, it is very difficult to match pantone colors to a high degree of accuracy, not all garments discharge the same. In addition, there can be variation between lots of shirts even when using the same style from the same manufacturer at a later date. Redyed shirts from manufacturers are not uncommon, and contribute to this issue greatly. This can make it difficult to run a reprint of the same art with exact color accuracy.

Certain garment colors and brands do not discharge well, and since discharge activator only works on cotton fibers, 50/50 blends and triblends do not discharge nearly as well as 100% cotton garments. With that being said, some very interesting effects can be made when you use a discharge ink on a blended shirt. With any ink system, testing is key to achieve the desired results. If you are wanting to use discharge ink on garment colors such as blue, purple green, or any blended garment, you should anticipate a bit more time for testing.

The ink components are often lower in price when compared to plastisol ink, however the cost per print is often more, due to the testing, additional time required for mixing, and extra documentation for each ink blend. In addition, hardeners are needed to strengthen the stencil on the screen, as the inks are very hard on emulsion. Since waterbased inks use water as a solvent, they also have the ability to dry in the screen. Some printers will use lower mesh count screens for this reason, the end result is detail limitation. This is a poor trade off, since the proper use of retarding additives and thin thread mesh, high LPI halftones can be easily achieved. But only when good materials, techniques, and planning are employed.

Often it is advantageous to utilize multiple ink systems and use discharge ink in conjunction with plastisol. Printing a discharge underbase, with plastisol top colors can give you a very thin ink deposit, with a soft hand and great detail. This combination technique works especially well with process and simulated process printing on soft rungspun garments.

Every piece of artwork is unique, and requires a high level of skill to get the best result. There are advantages and disadvantages of every ink system. The more you know about each system and the substrate it is being printed on, the better you can plan your artwork and garment selection to achieve the results that you want.