What sort of setting is everyone using to press a DTG shirt? We have a Digital Kiosk and press ours at 325 for 35 secs. I have seen where some people are having issues with how steadfast the colors are. I printed 60 shirts for a bible school last year and see them wearing them over and over again a year later and they still look quite good. I would guess that they have been washed at least 30-50 times. But... I am kinda picky also... I almost always run my shirts through for two passes to get the colors to stand out.
The time and temp I use was recommended by the manufacturer. It has been a year, but it seems to work. I have some shirts that are a year old and still look good. With few exceptions, I run all shirt through twice to make the colors stand out more. I think that may make a big difference.
I also double pass most prints to get good color. If you want your prints to be even brighter try pretreating your white shirts with laundry sizing. You can buy it at the local grocery store. It comes in aerosol cans.
Dry it in 3 second intervals until dry. It will make your colors really pop.
Interesting indeed.... I already have the stuff. We use it to take out hoops marks for the embroidery. Can you explain a little more? Are you spraying the shirt then pressing it to dry it, then printing? Does it affect the washability of the shirt, as far as holding the ink?
I have wash tested and uv tested it and it works great. If anything it improves washout a little. My theory is that it flattens the fibers on the shirt allowing the ink to penetrate to the base of the fibers.
I place a shirt on the press and prepress for 3 seconds. Spray the shirt with sizing until it is damp. Cover the shirt with untreated butcher paper or Quillon coated parchment paper and press for 3 seconds. Remove the paper and press for 3 seconds. At this point you can set the shirt aside for a few minutes and allow it to air dry or continue pressing at 3 second intervals until dry.
You don't need the paper to test it just press and go but it will start to build up on the bottom of your press. I haven't tried it using a Teflon pad but it should work.
Heat press time 
