There are two main types of ink that are used for textile printing. Water-based Printing Ink & Plastisol Inks. The detail of each Ink is discussed as follows: Water-based ink utilizes either dyes or pigments in a suspension with water as the solvent. The evaporation of the water is necessary to set or cure the ink. This curing can take place either at room temperature or using a forced-air dryer depending upon the specific water-based ink used and the speed or volume of production. Plastisol ink is PVC (Some inks are Phthalate-free) based system that essentially contains no solvent at all. It is a 100% solid ink system. Plastisol is a thermoplastic ink in that it is necessary to dry by heating the printed ink film to a temperature high enough to cause the molecules of PVC resin called Gelling and plasticiser which cross-link and thereby solidify or cure. Temperature at which most "Plastisol" Inks for textile printing cures at is in range of 160°C to 200°C.
Plastisol is the ink of choice for printing of finished goods such as T-shirts, sweatshirts, jackets and tote bags. Water-based ink is the choice for the printing of yard goods; either in piece form or on the roll. Both inks have technical advantages and disadvantages for use in specific applications. They also have their own environmental impacts and these should be considered for the particular application and shop set-up. October 2008 > SCREEN PRINT INDIA
Technology Advantages of Plastisol waste Plastisol is a very simple process.
Type of Fabric/ Usage
Usage Recommendations Plastisol Water-base T-Shirts/Light Colours Excellent T-Shirts/Dark Coloured Good Poor Nylon Jackets Good Poor Woven/ Towels Poor Excellent Sporting Goods Excellent Poor smear the ink.
Plastisol ink also creates an ink film on the Surface of Fabric that can be felt with the hand. The, higher the opacity of the ink, the thicker the film
Plastisol Inks can be left in the screen for extended periods of time without clogging of mesh. It is ready to use right out of the container more than 90% of the time. In most applications, it can be printed wet-on wet, which allows for increased production speeds. It comes in formulations that can be printed on light and dark fabrics. The disposal of:
Ink Type Water Base Medium Plastisol Inks Properties
Dries Fast Low & Medium Low Medium / Medium Easy
Print Ease Easy
Opacity Low- High
Hand/Feel Medium- Heavy
Curing Easy Ink Recovery. This thicker the film layer is Easy layer considered a disadvantage at consumer level.
One of the most important practices when using Plastisol ink is to keep the ink clean. What this means, is that it is very beneficial and cost effective, to keep Plastisol colours from being contaminated by dirt or even other colours of ink. By maintaining clean shop practices, there will be a great reduction in ink wastage. Clean ink can be returned to the original ink container for reuse. There is no Degradation in the quality of Plastisol as long as it is not mixed with other colours or contaminated with foreign materials. Plastisol that has been contaminated with other colours can still be retained in a separate container for blending with other waste inks. Many times this waste ink can be used to create new colours or it can be over pigmented with fresh pigment to create a dark colour, such as black, for use on less critical jobs.
If the Plastisol needs to be disposed of in an uncured state, then hazardous chemical regulations apply for either cured or uncured disposal. The biggest environmental hazard in the use of Plastisol comes in the screen and equipment cleaning steps. In order to emulsify the ink for easy removal from screens, squeegees and other work surfaces, it is necessary to use some type of Solvent. Waste ink and the solvent must be disposed of properly in order to minimise environmental impact.
The screen printing industry has been very active in the creation of products that can minimise the impact of these cleaning processes. Solvents are available that are 'more' environmentally sensitive than the traditional petroleum based solvents.
Water-based Ink Systems 'MAGIC 5000 Series'
Water-based inks are defined as those that utilise water as the main solvent. That does not mean, Plastisol does not dry. In order for a compound to dry, there must be evaporation of some kind of solvent. Since Plastisol has little or no solvent, it cannot dry. Because of this characteristic, Plastisol can be left in screens; the lids can be left off of the ink containers (although keeping them covered is a good practice to keep lint and dirt out of the ink). And ink left at the end of the job can be returned to the container for reuse without any adverse affects.This last practice is a great benefit in reducing waste product. Plastisol is extremely versatile in that most printers never have to amend the ink. They are able to use it direct from the container without ever adjusting the viscosity or the strength.