Whether you are using a Wagner sprayer and doing it by hand or have an automatic pretreatment machine like the Peal PTM it's important to test the different pretreatments AND different shirts you use so you can dial in the amount of pretreatment needed for a perfect white ink on dark shirt print.
If you use the Wagner sprayer you might want to look at the Lock and Go Pretreatment Canister for Wagner Sprayer attachment because the standard spray nozzle might put out too large of a droplet size of pretreatment and you end up over pretreating your shirt.
So here is what WE do to TEST different shirts and pretreatments. (Ex: if I'm trying out a new pretreat or a customer requests a shirt I haven't tested).
- I take the shirt and using heat resistant tape, divide the shirt into three sections.
- I spray each section with pretreatment in different amounts and cure it.
- If I'm pretreating by hand, I do a quick spray, longer spray, and then maybe soak the last section.
- If I'm pretreating with an automatic pretreater, I cahnge the density or settings from low to high.
- I print the same design or test lines in all three sections and cure that, usually that's all I need to do to get an idea of how much pretreat to put down.
- 4th step would be to wash the shirt twice. I do this mostly on new poly blends or poly sweatshirts because the immediate print can be deceiving.
When spraying a shirt, you really want to go for consistent full coverage in an area. You can make a template out of a cardboard sheet with a 16x20 open cut out area to control over spray.
Standing a certain distance away and going from left to right and up and down WITHOUT soaking it is hard. It's all about the spray coming out of the nozzle, the distance away and angle of the shirt.