Pretreating Dark Garments
For dark garment printing, the most critical process is proper application of Pre-treatment Solution onto the garments. Spotty or improper application of the Pre-treatment or improper drying will result in white ink not bonding properly with the garment fabric. This in turn will cause poor image quality and premature wash out of the image.
You will need the following for Pre-treatment Application.
- A well ventilated room. Good ventilation is essential for worker comfort and health. Application of Pre- treatment Liquid outdoors is not recommended on windy days as it can cause uneven application. It is recommended that a room away from the printer be dedicated to the application of pre-treatment so that the spray will not affect your printer.
- Our recommended process for applying the Pre-treatment Liquid is to use a High Volume Low Pressure (HVLP) spray gun. These spray guns are commonly used for applying paints and are available from paint supply stores or home improvement stores. The Wagner Control Spray Gun (Figure 7.4-1) and Campbell Hausfeld Paint Sprayer are good choices.
- Dilute the PowerBrightTM Pretreatment Liquid with a 2:1 ration amount of distilled water, 2 parts pretreatment: 1 part water. Fill the sprayer reservoir with the mixture. It is very important to use distilled water as city water, well water or filtered water may have mineral content that can affect the performance of the pre-treatment.
- Lay down the garment on a flat spray table. Make the garment even and flat.
- Apply the pre-treatment mix with the sprayer. Apply an adequate and even amount to where the material has an even wet sheen. Remember you only need to apply the pre-treatment to the areas that will be printed on.
- Going in only one direction use a plastic squeegee to help spread the pre-treatment evenly after spraying. This also flattens any fabric fibers that may have risen due to the application of the wet pre-treatment.
- Dry the garment, you can achieve an excellent result by letting the garments air dry or you can use a heat press in the hover position (This means the heat press is not closed but has a 1 to 1/2 inch gap toallow the steam to escape), blow dryer or a heat tunnel. Do not dry your garments in a tumble dryer. These dryers are full of lint and since the pre-treatment is wet and somewhat sticky you will end up with lint stuck to the pre-treatment.
- Once the garment is dry to the touch you can print on it. If you plan on storing the garments for later use, be sure that they are completely dry beforehand to prevent mildew.
- When first attempting the pre-treatment process test with a few shirts to determine how much to spray. Too much pre-treatment can leave dark areas on the garments. Too little pre- treatment can make the prints look dull. The performance of white ink is highly dependent on proper application of pre-treatment.
- Ricoh DTG offers Pre-Mixed Pretreatment if you do not wish to dilute your own pretreatment