Top 8 common printing mistakes

Screen printing is the process of pressing ink through a stenciled mesh screen to create a printed design. It’s a popular technique used in a whole range of promotional products. But Over 15 years I have given thousands of classes and been in hundreds of screwed up printing case “ the printing is bad”

I use to joke to my colleague than in a lot of cases I could have “phoned it in.” That means that in many cases I encountered the same problems over and over and over. I could have given them this article instead. OK, there is more to life in screening than “Top 8 Common Printing Mistakes.” The following is a list of things I am very passionate about. If you want to have a perfect screen printing then please read this list and see where you fit in.

Mistake #1: Art problem before you make a setup

A.  Start with good artwork, properly prepared. Don’t use a low resolution jpeg and think you will get a good screen print out of it. The art should be a minimum of 300 ppi at print size. 

B. Make sure you can print the design correctly and match it with the correct screen mesh for the artwork. 

C. If you have a customer, make sure they sign an approval of the final design. You’d hate to reprint a design at your own expense because a word was misspelled!

Here's a nice design made to look distressed. (a new design we are testing)

Mistake #2: Screen Exposure problems-The emulsion does not go onto the screen smoothly and evenly. 

A. The mesh may have loosened up and have uneven tension. This is especially a problem with wood frame screens once they start to get old. 

B. Your emulsion may be old or have dried bits that have fallen into it. Keep the emulsion container clean and try to refrigerate it if you are not going to use it up pretty quickly. Check the shelf life of the emulsion you are using. 

C. Have you remembered to remove the rubber edge protector on your scoop coater? Don't laugh! You’d be surprised how many people make this mistake. 

Mistake # 3-Losing fine detail when you burn screens.

A. The transparency may not be making good contact with the screen. Make sure you place the transparency with the print side next to the screen and weight it well enough to make good contact. A vacuum exposure unit is best, but if you don’t have one of these you have to be more careful. 

B. The screen is over-exposed. If the exposure is too long, the fine detail will not wash out and will be lost. 

C. The light you are using to expose the screen is not angled correctly. The light source needs to be as straight on as possible, in other words, 90 degrees to the screen. 

D. The light source may be too weak. If you are using a weak light source and a long exposure there is more risk of ambient light or light scattering contaminating the exposure. 

Mistake # 4 Bad registration - 

A. Screens can become loose in the bracket on the press if not tightened enough.

B. The platen might be moving if the screw is not tightened enough. Turn it as tight as you can be careful not to strip it. 

C. The shirt might be moving if you don’t have enough adhesive on the platen. 

Mistake # 5. Screen break down - 

A. If the screen was underexposed, the emulsion can loosen and come off. We always “post-expose” the screen. Which means we either place it in the sun after it’s been washed out and dried or we expose it again in the exposure unit to set the emulsion.

B. The squeegee can wear through the emulsion on a long print run or on a screen that has been used a lot. If the worn spots are outside of the design area you can clean the screen, spread a thin coat of emulsion over the worn areas and expose it to repair the bare spots.

Mistake # 6  Bad ink curing, ink under-cured or over-cured - 

Check the curing temperature with a temperature gun. And know what temperature the ink is supposed to cure it, of course. I usually print out a sheet of instructions that go with the ink and stick it to the lid of the ink container.

Mistake #7  Incorrect squeegee angle -

A. Try for a consistent 45-degree angle when applying ink to the screen. The ink goes on pretty smooth at this angle. At an angle of 60-degrees or more, the ink may not get through the mesh correctly and evenly. An angle of 30-degrees or less can make the ink print too heavily onto the fabric. 

B. You may need to experiment with the squeegee angle and practice to get it right, see what works for you and keep it consistent. You can also experiment with a “push” print stroke as opposed to the usual “pull” print stroke. There are cases when a push stroke can be useful. But always do one or the other, don’t switch between strokes. 

Mistake # 8 Too little ink is getting printed onto the products

A. You may be using too much pressure. Don’t press down too hard on the squeegee and use even pressure all the way across the print. 

B. You may have gotten too much ink into the mesh on the back flood. Be careful as you back flood and don’t press down too hard or go over it too many times. If your ink does get too heavy, pull a few prints on test sheets without back flooding to clear out the screen. 

C. The ink may be too thinned out 

D. You may have an old squeegee with edges that are rounded and need to be sharpened.

Here is a picture shows the ink is too little cover the black color