All direct-to-garment printers use a water base ink system and special treatment is required when printing dark shirts. The rule is: When you print white ink, you must pretreat the shirt first. Without pretreat solution on the shirt, the white and color inks will simply disappear into the fabric after printing.
White shirts need no pretreatment, plus ash grey and some pastel shirts may not need pretreatment either. We say “may not” because the translucent CMYK inks can take on the color of the shirt being printed. (A blue ball printed on a yellow shirt may appear green.) So, if the image is not impacted by some color shift, no white underbase with pretreatment is required. If you need to match colors exactly, then pretreatment and white ink even on pastel colors may be necessary.
There are special pretreats available for light shirts, even when you are printing CMYK only without white ink. These pretreats will aid in a brighter image and better wash-ability, but are not required for a salable finished product. Use of this light shirt pretreatment is simply a personal preference choice on the part of the operator.
Pretreatment is best applied by either a hand held power paint sprayer, or by using an automatic pretreat machine. The choice between the two is usually budget related.
If you pretreat with a hand held power sprayer, you must accomplish this task in a separate room from your printer. You need to protect the print head from any pretreatment spray floating in the air. Hand pretreating will do the job with a little practice, but can be messy and inconsistent. Most operators who hand spray pretreatment tend to lay down too much pretreat solution on the shirt.
Pretreat application using a “fully enclosed” automatic sprayer can be done in the same room with your direct-to-garment printer. This is the most consistent, cleanest method of pretreating your garments. Using a pretreat machine will help to remove the “pretreating variable” out of the formula to a high quality final image.
Shirts can then be either heat pressed dry immediately after pretreatment is applied, or can be hung to air dry. If you air dry, press the shirt for about five seconds before printing to flatten the fibers of the shirt for ideal image. Most operators will pretreat large quantities of shirts to have in stock. You can pretreat your shirts even months ahead of production with perfect results.
TerryCombs.com 
Does the pretreatment need to cure at a certain temperature or is the goal of heat pressing it just to dry the pretreatment?
The temperature doesn’t matter. You are correct, we’re just trying to dry the pretreat solution.
Hi Jason – The box is usually a result of one or two steps in the process. First, many operators use far too much pretreat solution, so try backing off on the amount of that product. And second, too much pressure on your heat press can be the cause as well. You should be using light pressure to cure the garments. Hope this helps!
Thanks Terry. I appreciate the help.
Hi Terry, great info here.
Quck question about those pesky “pretreat boxes” — is there a surefire way to get rid of the “pretreat box” while using a manual heat press?
The best solutions all come with issues: hover dry (can take too much time), hang dry (can’t print until the next day) or belt dryer (don’t have one). Is there a way to not just reduce/minimize this pretreat box, but get rid of it completely while still using a manual heat press and clamping it down?
I have read a bunch of different tricks, but can’t say any of them really work all that well and I still am left feeling like I need to wash the tee before selling it. I’ve also considered that maybe my time or technique is off, but I’ve tried a bunch of stuff and still get the box.
Thanks for your help.
Is there a guide to how much pretreat you should use based on not only color but also whether you are printing on t-shirts, sweatshirts, or jackets.
Hi Gwen – Unfortunately there’s not a specific guide for the amount of pretreat since application methods differ. Using the SpeedTreater-TX from Equipment Zone as an example, basic t-shirts are generally set at 50% (the halfway point on the dial). Sweatshirts and heavier items will be set at 60%. Of course these are basic settings and some experimentation with new styles, brands and fabrics will be required. Hope this helps!
Terry, what I don’t get is why are we still pre treating these shirts? Direct to garment is very popular these days and is becoming bigger and bigger in our industry.Why aren’t companies like Glidan, Hanes ect. selling pre treated shirts? It seems like a no brainer and would make it so much easier for us, I don’t get it…
Stuart, I believe that shirts already pretreated are the future, but it’s not today. There are some pretreated shirts on the market but they are 2-3 times more expensive and the coating is marginal at best. For instance, there’s a disclaimer saying “not for white only prints” meaning the image will not be opaque enough. The first step is that most manufacturers are bringing a DTG shirt to market. That’s happening now. The next step will be a shirt with pretreatment applied. Hopefully the window for this happening will be short.
Hi Terry~
We have a DTG Summit 520 printer that needs repaired. We believe it has a collapsed head. We are 45 minutes out of Pittsburgh and need to find a repairman or technician. Do you know of any?
Hi April – Your best bet is to contact Mesa Distributors in Ft Worth, Texas. They sold that machine originally. Service & Support: 800-330-3867
Hi Terry,
We are using DuPont Artisti ink printing on 100% cotton shirts (Hanes) and use a manual heat press. For black shirts we cure ink at 350 for 90 seconds with very light pressure, twice. For white shirts we cure ink at 330 for 40 seconds with very light pressure, twice. The issue we are having is what temp/time to use for curing on other colored shirts. For example, on a gray shirt that has been pt’ed and white ink was used in the image, if I use 350 for 90 sec, the shirt will burn. Very frustrated.
Hi Brad – My experience with DuPont ink is 330F for three minutes, light pressure, dark shirts. On light shirts, I go 330F for 90 seconds, with light pressure. The rule of thumb to follow is a shirt is considered dark (longer curing time) anytime you use white ink. I would back down from the 350F and buy thermal strips to test that your heat press is not hotter than it is displaying. With other inks curing faster, DuPont may have other recommendations today. Hope this helps!
Hi Terry,
I use Brother industrial DTG printers. One of my customers just sent me pics of shirts that I made her on my Brother GT-361 with white ink. I use ( The Cube) Pretreatment Machine to apply the pretreat solution. I have had this issue with only this particular customer. I printed white ink onto pretreated light blue tee shirts. I heat set the ink for 35 seconds @ 356 degrees(recommended by Brother ) for all heat setting their inks. What happened is the customer waited over two weeks to wash the shirts then advised me you can see where the shirts were heat set because the light blue shirts was changed to a darker color.almost like the original shirt color was compromised from the pretreatment. Now I have to remake the shirts and I want to be able to tell my customer why that happened. And to keep this from happening again in the future. Any clues or ideas on why this happened to my shirts
While I don’t have experience with the Brother printer, I suggest you try light shirt pretreat from Image Armor (http://imagearmorpt.com/) and try to cure at 330F. Of course you should wash test afterward. Hope this helps!
Hi Terry, below are on black shirt with white base ink
Im using a direct ink dark pretreatment on 100% ringspun from cotton heritage. Using a pearl ptm density set at 35. Hotronix temp at 330F and pressure of 6, 3 presses at 20 seconds each. Ink lays down perfect but after wash there are white fibers visible on the pretreated area. What may be the problem?
Michael, seeing white in the pretreat area after heat setting/washing generally means too much pretreat has been applied. I would try backing off on the laydown and do some testing.
Im using the Pearl PTM and the lowest setting is 20, tried it and the pretreat marks are still visible right after curing the pretreat and also still visible after curing ink. are there are variables that i may try adjusting?
Hi Michael – What pretreat are you using? And when you say the pretreat is still visible, how do you mean that?
The box area where the heat press presses down on the shirt in the area where it was preatreated. color is usually lighter than the color of the shirt.
i’m using the Dierct Ink (Dupont Artistri) pretreat
What is your favorite pretreat for the speedtreater? We started with image Armor and then got some Epson. Still not sure which is going to be best for us. We don’t get a “box” with Epson, but are getting inconsistent results at times. Mixed 1:2 but then added another cup to that firest qt mix.
Thanks
Hi Jeanne – I see similar results with both the Epson and Image Armor pretreat. It’s important to shake the pretreat before you use it each time, and too shake the Epson pretreat before mixing with distilled water. If you’re seeing a “box” it’s likely too much pretreat. Most people use too much. Do some experimenting with less.
Do you need to pretreat if you are printing black ink on a light pink or light gray shirt(100% cotton)?
Hi Kat – You don’t have to pretreat a light shirt with black or dark ink. Some people do to achieve a brighter image but not required. The only time you must pretreat is when you are printing white ink.