Here is a list of design elements to avoid when designing in Illustrator for T-Shirt art.
As T-Shirt printers and art separators (the function of separating the image colors into individual spot color plates) there are several design elements we would prefer not to see in a file for print quality and ease of use.
No outlines please. In general, outlines can be a real pain. On most shirts an underbase needs to be printed and outlines can cause all sorts of issues when creating the underbase plate. Especially if different stroke sizes were used in the design concept. Also quite often strokes are not set to scale with the image and if scaling happened between the design process and arriving at your printer you will have major changes happen to the design. So in general it is always best to create files without outlines or convert them to objects before submitting files to your printer.
Avoid all the special effects that illustrator has to offer. OK maybe not all but most of them cause problems for the separator and don’t really do much for t-shirt printing effects. Refer to our Bold is Best post for more insight. Illustrator has become the standard in the industry for print design and all those effects translate beautifully to paper but not so much when screen printing. Remember that screen print for the most part is a simulation of process printing and spot colors and blended spot colors are used for nearly all screen printing. So what should be avoided you ask? Drop shadow is troublesome in that it does not scale properly so if a design is created at 8 inches and now needs to grow to 11 inches for a shirt problems will occur. Transparencies is another. Lets say you have a solid red and overlay that with a transparent yellow. Several things are going to happen. First it is important to understand that an ink does not print transparent but will print as a halftone to simulate a transparent ink. The transparent yellow is not going to print very saturated in the areas that are not overlaying the red, the orange created by the red and yellow will not print very saturated compared to the other spot colors in the design, the orange created by the combination will not be any kind of pantone match.
Limit the color pallet and use spot colors. It is very common to get files from redraw agencies that violate the No Outlines Please rule excessively and then use every cmyk color in the pallet. This can cause tremendous rework time by the separator and can nullify all the cost savings of having this function performed by outsourced agencies. Designing with a predefined pallet is essential to the WOW factor of the design and ease of output to film. Always make sure your designer is experienced in T-Shirt art and the effects it will have on the final product.