Plastisol Ink: General Information

Plastisol Cure Variables

Size and Thickness of the Imprint

When printing a design directly on a T-shirt, a good starting point would be 1 1/2 minutes at 320°F (160°C). A large athletic number printed on stretch nylon might require as much as 2 1/2 minutes at 340°F (173°C). The greater the volume and/or thickness of plastisol on the garment, the longer the time and/or the higher the temperature required.

Color of the Ink

When fusing light colors (white, gold, etc.) under infrared lamps or solely infrared conveyor dryers, slowing down the belt speed may be necessary. Light colors may reflect infrared heat sources. With forced air/infrared dryers, color is not that important, but watch reds & blacks for undercure.

Composition and Type of Fabric

The heat required to cure a plastisol imprint on a heavy cotton duck tote bag will be greater than the same design on a T-shirt. Many fabrics contain varying levels of moisture, water repellents, wetting agents, etc. Most fabrics containing any of the above would absorb more heat, and therefore a higher temperature or a longer dryer cure time would be required.

Type of Dryer for Fusion of Plastisol Inks

As mentioned previously, watch carefully the difference between infrared and forced air dryers. Several variables related to oven cure are:

Scorching - If your dryer is too hot it may scorch or discolor the garment you are curing. The answer is to lower the temperature to minimize scorching.
Dryer Hot Spots - Most conveyor dryers have varying degrees of efficiency. Gas burners malfunction and electrical sources burn out. Heat strips are essential in determining dryer efficiency.
Effects of Overloading the Dryer - Dryer efficiency is reduced when the belt is completely full versus sporadic usage. Increase the heat to reflect overloading in the dryer.
Weather and Plant Environment Conditions - High humidity in the plant in colder months will reduce dryer efficiency. If a problem with cure is encountered, check all environmental variables.

Special Problems of Plastisol Inks

Polyester Fabric Dye Bleed or Migration

Polyester Fabric Dye Bleed or Migration is directly related to plastisol cure. Most polyester fabric dyes are relatively stable below 320°F (160°C). Once the fabric reaches this temperature or greater, the dye sublimates or turns into a gas. The sublimation process is the primary cause of those pink plastisol designs, when white is printed on red polyester fabric blends. By properly controlling the oven temperature, polyester bleed can be minimized. Excalibur's 596 Miracle White is a new generation of low bleed plastisol which will greatly reduce or eliminate dye migration and bleed.

Synthetic Fabric Adhesion of Plastisol Imprint

This is a problem that must be followed very carefully. Some fabrics contain certain residual chemicals that function as release agents, or the fabric type is very incompatible with the plastisol. In these cases where adhesion to fabric is a problem, cure the design as hard as possible without scorching. Another suggestion is to add a low percentage of Excalibur's X100 Bonding Agent that can be mixed in with the plastisol ink.

Obtaining High Opacity on Dark Colors

Opacity is directly related to the thickness of the imprint, type of fabric and dryer cure. To obtain good coverage:

Control the Thickness - Proper selection of mesh size - 50-60/inch (20-24cm) - squeegee type (medium durometer rounded), and the viscosity of the ink will lend to excellent coverage. The viscosity of the ink is crucial to laying the imprint on the surface of the garment. Fabric type and squeegee pressure will affect penetration of the plastisol ink into the fabric's fibres. The best technique possible is to lay the ink layer on the surface of the garment. The thicker the imprint the better the opacity. Often a white base image will be used to obtain good coverage on multi-colored designs. Many athletic jerseys are printed with meshes as low as 30/inch (12 cm) to achieve very opaque and durable numbers.
Type of Fabric - To obtain good coverage on dark polyester fabric blends, cure the plastisol at 325°F (163°C) or below. Remember, if 325°F (163°C) is a lower temperature at which you normally cure, increase the dwell time in the dryer to ensure total cure.
Run Excalibur's 596 Miracle White as a first down color. This will eliminate or reduce most bleed problems due to dye migration.
Checks for Total Fusion or Cure - Remember! When plastisol imprint reaches a temperature of 310°F - 330°F (154°C - 165°C) total cure is achieved. Plastisols are thermoplastic (soft when hot) and any checks for cure should be made when the imprint is at room temperature. If the imprint cracks when flexed, improper curing is the likely problem. In cases where too much mineral spirits are added for thinning, the ink will not fuse no matter how long or how hot the cure.
1. Physically pulling and stretching the plastisol design is the best test of cure. Any cracking or crumbling indicates undercure. Check equal thickness throughout design, as the thicker portions will cure more slowly. Abrasion resistance or scratching the design is also a good check for cure.
2. Washability and/or adhesion to the fabric is a good check. If the plastisol was undercured the mechanical lock on the fibre will be weak and the washability poor.
3. Pigment crock or pigment migration to the surface is often confused with plastisol cure. In the majority of cases, when you are able to rub off the color, the problem is the initial mixing of the ink prior to printing. Vigorous stirring may be required.
Controlling Polyester Bleed - The most important factor to recognize is that all fabrics do vary. Check the garment to be printed prior to running the entire job. During the actual garment dying process, it is possible that the dye is not properly washed out.

To control polyester migration:
- Screen print as thick as possible.
- Cure at 325°F (163°C) or less if possible.
- Cool the garments as quickly as possible; place on hangers or use fans. Do not stack hot.
- Use Excalibur's 596 Miracle White as a first down underbase or free standing white.