Obtaining High Opacity on Dark Colors: Opacity is directly related to the thickness of the imprint, the type of textile fabric and dryer curing method. To obtain good ink coverage/opacity on the imprinted garment, please review the following topics to learn more:
The Type of Fabric – To obtain good coverage on dark polyester fabric blends, cure the plastisol ink at 325°F (163°C) or below. Remember that if 325°F (163°C) is a lower temperature at which you normally cure your screen prints, then increase the dwell time in the dryer to ensure there is a total cure of the printed garment.
Control the Thickness – Proper selection of mesh size – 50-60/inch (20-24cm) – squeegee type (med. 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 fibers. 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 sports jerseys are screen printed with meshes as low as 80/inch (32cm) to achieve very opaque and durable numbers.
Controlling Polyester Bleed – Begin by using a good quality low bleed Ink such as 596 Miracle White. It is also important to recognize that fabrics will vary from one dye lot to another. It is highly recommended that a print test run is performed prior to starting production.
To Control Polyester Migration – To control polyester migration or a print, please follow these steps: 1) When printing do not force the ink through the fabric. Allow as much ink as possible to sit on the material. This will give you better opacity and will allow the ink to cure faster. For better ink opacity you can print/flash/print if necessary. 2) Cure at 325°F (163°C) or less. 3) Cool the garments as quickly as possible: place on hangars or use fans. Do not stack hot. 4) Can be used as a first down underbase or as a stand alone white.
Run 596 Miracle White as a First Down Color – This will eliminate/reduce the majority of bleed problems due to dye migration that are common in today’s industry.
Checks for Total Fusion or Cure – When the plastisol imprint reaches a temperature of 310°F – 330°F (154°C – 165°C) total cure has been achieved. Many plastisol inks are thermoplastic (soft when hot) and checks for cure must be made when the imprint is at room temperature. If the imprint cracks when flexed or stretched, improper curing is the likely problem. In cases where too much mineral spirits or non-curable reducers are added for thinning, the plastisol 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 on the entire design, as the thicker portions will cure more slowly. Abrasion resistance/scratching the design is a good method to check for proper cure.
2. Washability and/or adhesion is a good check. If 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. It is also a sign that the printed garment is undercured.
Polyester Fabric Dye Bleed or Migration: Directly related to plastisol curing. Most polyester textile fabric dyes are relatively stable below 320°F (160°C). Once the fabric reaches this temperature or greater, the dye sublimates or will turn into a gas. This sublimation process is the primary cause of those “pink” plastisol designs when white is printed on red polyester fabric blends. Proper oven temperature can greatly minimize polyester bleed. 596 Miracle White is a brand new generation of low bleed plastisol inks which will greatly reduce or eliminate dye migration and bleed.
Synthetic Fabric Adhesion: There are some textile fabrics contain certain residual chemicals that function as release agents or the fabric type is incompatible with that particular plastisol ink. Where adhesion to fabric is a problem, heat cure the design as hard as possible without scorching the fabric. Generally, plastisol ink will adhere to most knitted, textile fabrics.