How to Expose a Screen in Screen Printing?

by Kevin Cook| in Printing Business on November 24, 2021 3259 /

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Last Updated on: 29th March 2024, 08:00 pm

It is better to follow this procedure during the night. Use safe light conditions to carry on this process. Parts of the process need to be done in safelight conditions. For washing out the screen, you will need a garden hose with pressure.

Moreover, you can also use a jet nozzle or a water blaster, or a pressure washer. You can use any of the options to wash screens.

Tips to Expose a Screen in Screen Printing:

Now follow the steps below:-

1. Pack the foam on the underside of the screen:

Switch off all lights and use a safe light to carry on the process. Under safelight conditions, get out your screen coated with photo emulsion, although dried over time. Put the foam packing on the underside of the screen.

Now, place the screen in the centre of the black cloth, keeping the foam down and the screen up. Thereafter, place the artwork on the screen so that the art will print on it. Finally, place the glass over the artwork so that it holds it flat against the screen. Turn on the 500-watt work-light and expose the screen for 5 minutes.

2. Turn on the 500-watt work-light and expose the screen for 5 minutes:

After a lapse of five minutes, switch off the 500-watt work-light. Then turn on your safe light. Could you take out the screen and wash it? Therefore, it is better to do this process at night to prevent damage to your screens.

After that, soak your screen with water on the soft spray. Then use a water hose to force out all the unwanted emulsion from your new stencil. Be cautious while using a high-speed washer as the force may damage your screens.

3. Register Films:

Before we go to the exposure we need to register our films. That means you need to place both of these two color films in the exact spot or very close to the exact spot on every frame.

We’re going to use a pre-registration system in order to more accurately and efficiently do this for placement. Of course, center prints going on the center of the garment are typically placed on the upper 1/3 of the open mesh area.

If you’re placing your films manually you set your film upside-down on the screen mesh.

So that if you look through the inside of the screen to the outside you see your positive image area for one color designs.

4. Lay down film onto exposure glass:

Simply lay down the film on the exposure glass and place the screen on top of it with the image area in the approximate spot.

The screen squared up with your film for multiple color designs you want to be more exact while you can’t align your film to each screen with a measuring tape and a t-square.

It is much easier to use a template so you can place your film onto the correct platen position. And then place your screen on top of it you can do this by using double-sided tape.

Put a sharpie mark in the center of the top and bottom registration marks.

Then you can place all your films using those striping marks and tape the film directly to the screen.

Make sure to use clear tape that’s the body to it.

So you can easily remove it later.

5. Expose the screen:

Now that our film is aligned it’s time to expose there are two things needed for great screen exposure.

First is the proper amount of exposure time for the light to penetrate all the way through the emulsion and second is positive contact between your glass your film and your screen mesh.

Moreover, the amount of time it takes to expose your screen is directly correlated to how much UV light comes from your exposure unit.

The entry-level unit has 30 watts of power whereas the high-end exposure unit has 450 watts of power.

These units going to be more accurate and faster because of their single-source higher wattage bulb.

As we discussed before positive contact is key in creating good exposure.

6. Create your own positive:

An open-top glass unit requires that you create your own positive contact. You create it by using pressure that pushes the film in the screen mesh together.

You don’t have pressure like an easily leak it’s a way around the edges of the image and create a blurry or underexposed stencil.

On the open face glass unit, you want to use the sheet of foam that comes to the unit and put it inside the mesh.

Then you put a piece of wood or metal over the film.  It evenly distributes the weight. Then you put 50 pounds of pressure on the top.

It pushes the screen to mesh the glass and sandwiches the film in between creating a great positive contact.

More advanced units use either leverage to push the glass and the foam together or a vacuum to suck down the mesh to the glass.

Regardless of which unit you have the key here is positive contact throughout your image area.

7. Direction of light:

The next thing that affects the image detail is the direction of the light that exposes the screen.

It is great for overall coverage but as the light hits the small detail points such as halftones it can cross expose them this is why we used a 5 X multiple for mesh.

It gives us some buffer space for direct light source units.

The directional light and more power allow you to expose better screens faster exposure times are typically available for your emulsion mesh and explosion.

You can find these on the product page on screen printing calm these will give you a starting point from there there are few tools and science dial in your times the goal is a good exposure to allow your UV light to penetrate all the way from the front to the back of your mesh.

8. Exposure calculator:

An overexposed screen means that your light penetrates too long and starts to expose your image area. Thus, making it difficult to wash out its underexposed screen means that your light is not allowed to penetrate long enough.

It will leave your modulus slimy on the back end to allow residue to drip into your image area and means your screen could break down on press to calculate proper exposure.

We recommend the use of an exposure calculator this simple exposure calculator called a step wedge test measures the density of the exposure by different levels of black filters on the strip.

The goal of this step wedge is to expose to the seven mark if you are under a seven mark this means that you are overexposed if you are over a seven mark.

Create a board put your exposure times on it that way as you’re downloading your exposures and you’re adding people to your darkroom operations.

You know what your exposure times are and you can keep track of things as they move forward likewise been exposing halftone detail.

9. Include Halftone gradient scales:

It’s always a great idea to include halftone gradient scales on the side of the image.

It allows you to easily see if you’re exposing all the half tones correctly. If you’re not capturing all the half tones.

Lower your exposure time or raise your mesh count.

For high mesh gradient print expose your 230 mesh screen for 7 seconds. After the screens are exposed

take it over the washouts they can get wet on both sides.

That will break down the unexposed area of the emulsion and develop the screen.

10. Wash screens:

After waiting a couple of minutes using medium to high pressure to blast up the image area.

Starting at the bottom of the image to the top of the image. Notice that you also spray from the flat or the shirt side of the screen because it is a stronger part of the emulsion.

Once your screen is exposed in your image area. Wash out your screen needs to dry.

If your screens were properly exposed all the way down you won’t have any residue dripping into your image area.

However, if you do you can still save your screen take a little paper

towel or newsprint and dab away that residue so get stuck in your image area.

Moreover, drive screens outside if it’s sunny out

However, you can also dry it in front of a fan. Moreover, you can also use a drying cabinet to go faster.

Final words:

By following the steps above, you can easily expose screens in screen printing.

While exposing screens seem to be time-consuming, it eliminates biscuits at the end.

Related Questions:

What are the consequences of over-exposing screens?

Over-exposing screens cause the residue of emulsion on the screen, which gets hardened in due course.

What is the cost of making screens in screen printing?

The cost of making a screen is $3 to $5. However, it may vary with the cost of screen mesh count.

What will happen if we overexpose screens?

Over-exposing screen hardens emulsion. As a result, it ruins the screen for further use.

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