Printing on 'flag' material with a solvent printer is far from ideal, particularly when long-term outdoor use is needed. In the USA, federal and state flags are traditionally produced using screen printing. These flags are always printed on nylon material. Nylon offers a very high degree of ink penetration, so the image looks similar on both sides.
It is possible to print onto uncoated nylon with a digital printer. The inkset that is used is called direct Acid ink, and it is water-based and not solvent-based ink. After printing, the ink needs several post-print activities, including steaming and washing.
To print onto 'flag' material with a solvent inkset, the media needs to be treated with a coating, much like what aqueous printers use when printing onto PVC. Many polyesters are closed fabrics, and don't permit a great deal of ink penetration.
The problem is that the coating degrades or delaminates over time, and the ink goes with it. Abrasion is often times a problem with these inks (wind whipping the flag around). The best solution is to outsource the production to someone who can direct print onto nylon material. Hope this primer helps.
Bob
