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Old July 27th, 2018 -   #11 (permalink)
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Default Re: Black T shirt advice

Originally Posted by TABOB
Not true!
As I've already said... a dry shirt will NOT take 3 minutes to cure. The reason Polyprint power inks do cure faster is because they contain more binder. Screen-printing inks with even higher binder content, can cure in 15-30 seconds when using a heat-press. Also the method of curing is important. A heat press will cure the ink much faster than a conveyor dryer.

In more detail:

First of all, I wouldn't be surprised if DuPont makes the Polyprint inks, as they do make inks for many brands.
Second, DuPont guidelines are 330F /165C for 120 seconds. However, these are ONLY guidelines, in an attempt to create one setting for as many types of fabric as possible. In reality the optimal settings will vary a lot.

A few examples:

  • A lightweight, 100% cotton shirt, can be cured in 50-60 seconds at 360F /185C. The same shirt, if damp, will need around 120 seconds.
  • A dry, lightweight poly-cotton shirt (5/95) will need around 90 seconds at 350F /175C... But a damp one will need 180 seconds.
  • A lightweight poly-cotton shirt (35/65) may need around 5 minutes or more at at 320F /160C. Dry or damp...makes no much difference in this case.
These are rough estimates of what I can remember from the tests I've done with DuPont inks. I ended up with a list of more than 50 settings, which kept growing, until I had enough with the regular DTG printing method, and gave up. I now use my own hybrid method, and only 2 settings for everything:
  • 100% Cotton: 50 seconds combined cure time at 360F /185C).
  • Poly-Cotton: 90 seconds combined cure time at 320F /160C).
Some tips:
  • If you are using a heat press, you should do multiple 30sec pressings, up to the time required, using the highest temperature the fabric and the ink can take. If are using a conveyor dryer, you should reduce the temperature, and increase the time as required to prevent charring the shirt.
  • Be careful with poly-cotton t-shirts. Too high temperature, and/or too much time, will make the fabric very fragile, and will fall apart with the first stretch... as you try to wear it for example. Don't forget to do a stretching test before starting to using a particular setting in production.
Thank you tabob, i have been experimenting with your advised setting (30 sec) and slowly but surely there is an improvement, i have gone from a 3 min press to 3x30 and 1 x 1 min, there is an improvement