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Screen Printing Underbase, 9 Tips
Screen printing and under base can be challenging. Here I would like to give you some tips on how to screen print a nice crisp under base.
Screen printing Mesh
Check what mesh count you are using, very often people use a standard 48 (110) mesh as a base. But this depends on your ink viscosity, if your white ink is more liquid, why not try to use a finer mesh? Have you ever considered an S mesh as it has a wider mesh opening and you will get more ink on the T-shirt?
Screen printing Ink
What background color do I need to cover? If you have a dark color shirt, like black, and you need a bright white. You would definitely need an opaque white. But if you have semi-dark shirt colors. A semi-opaque white might do the job. Check the background color first and then choose the right print color.
Emulsion thickness
Emulsion plays a big role in screen printing. You want an EOM (emulsion over mesh) of 10% or more. Not too high and not too low.
The aim is to create a nice even layer as a base layer on the garment, and a 10% EOM will do this for you.
The right Squeegee
The squeegee you use. A softer squeegee will deposit more ink than a hard squeegee. And consider a round-edge squeegee for water-based inks. A round-edge squeegee will again deposit more ink.
The amount of pressure
Don’t force the ink through the mesh. It is best to print with enough pressure. Just enough to shear off the ink and clear the screen, leaving the ink on top of the garment rather than pushing it through. (but this does not apply to transparent water-based paints, also known as binders.)
Important! The ink should stay on top of the garment and NOT penetrate the garment. If you print on the underside and see white when looking from the inside, you know the pressure is too high!
Stroke speed
Squeegee speed is important to print a nice white undercoat. Water-based ink should be printed rapidly. You want to pump the ink through the mesh.
Off Contact
Off-contact also plays an important role. Make sure the ink stays on the garment. 1mm of off-contact should be fine, but make sure the off-contact is the same all over the screen.
Newtons
Mesh, the mesh should be at least 20 Newtons. And it should be at least 20 newtons everywhere. You do not want one corner to have a different Newton value than the other. This will give you result of uneven white coverage.
Choke the screen printing under-base
If you have a registration problem. And your screen printing machine does not have butt-to-butt registration. Remember to choke the under base a little. Now the top colors will be easily covered by the underlayer. But be careful not to choke too much!
If you consider all 9 points, you will find it easy to print a nice soft base. Screen printing isn’t difficult if you follow these basic tips.
After printing the under-base screen printing
Do not flash too long the under base, you just like to gel the ink. Too much heat, on the under base can cause more problems afterward. Get the flash cure temperature right and the index time off turning your table. Many times I have seen over-flashing the under base. If the screen printing pallets heat up too much during production, the subsequently printed inks can dry more quickly on the screen. Especially water-based inks are very sensitive to it. you like to keep the temperature of your pallets low as possible. And the only way to check this is with a temperature gun. With this Gun, you can monitor your platen temperature and assure, that you keep the platen heat low as possible. This saves you many headaches in production.
