Screen Printing Exposure Units & UV Lamps

UV Exposure Units and Exposure Systems for Screen Printing

Screen exposure is one of the key stages in preparing a screen for printing. A suitable light source transfers the image from the film positive onto the photosensitive emulsion, hardening the exposed areas while leaving the image areas ready to be washed out and printed.

At Rittagraf, you will find different screen printing exposure units and UV lamps, ranging from compact LED systems for smaller formats to professional vacuum exposure units for printmaking studios, artists, schools and workshops requiring greater control and repeatability.

Choosing the right exposure system mainly depends on screen size, the type of emulsion being used, how frequently screens are exposed and the level of precision required.

UV LED Vacuum Exposure Units

Vacuum exposure units provide control over two essential aspects of screen exposure: the light source and the contact between the film positive and the coated screen.

The vacuum system keeps the positive in close contact with the photosensitive emulsion during exposure, reducing the loss of definition that can occur when there is a gap between the artwork and the screen. Good contact is particularly important when reproducing fine lines, small details, text and halftone images.

Our range includes different exposure unit sizes to suit the screen formats commonly used in printmaking and screen printing studios.

The 50 × 60 cm UV LED Vacuum Exposure Unit is the more compact option, suitable for screens with an internal size of up to 50 × 60 cm.

The 60 × 80 cm UV LED Vacuum Exposure Unit provides a larger working area for screens with an internal size of up to 60 × 80 cm.

UV LED Lamps and Lights for Screen Exposure

Not every application requires a vacuum exposure unit. For smaller formats, occasional screen making, beginners or studios looking for a simple and portable setup, a portable UV LED exposure kit can be a practical alternative.

These systems can be used to expose coated screens by positioning the UV light at a controlled distance and manually establishing the exposure conditions. Compared with a vacuum exposure unit, greater attention needs to be paid to positive-to-screen contact, distance from the light source and exposure repeatability.

Vacuum Exposure Unit or UV Lamp?

The right choice depends on the type and frequency of work, as well as the level of control and convenience required.

A standalone UV exposure lamp is particularly useful for beginners, smaller screen formats, studios with limited space and occasional screen making. It provides a simple and flexible way to establish your own screen exposure setup.

A vacuum exposure unit is more suitable when greater process control and repeatability are required, particularly when regularly working with fine detail and halftones. The vacuum system provides consistent contact between the positive and emulsion, while the timer makes it easier to repeat the same conditions once the correct exposure has been established.

Rather than there being one exposure system suitable for every application, the best approach is to choose according to screen format, frequency of use and the level of graphic detail required.

UV-A Light and Exposure of Photosensitive Materials

UV exposure systems are not necessarily limited to screen printing. Depending on the wavelength of the light source and the spectral sensitivity of the material, they may also be used for other graphic, printmaking and photomechanical processes.

Possible applications include compatible photopolymer plates, letterpress, flexography, photogravure, offset lithography, cyanotype and alternative photographic processes, as well as other UV-sensitive materials and processes.

Compatibility should always be checked for the specific material being used. The fact that a photosensitive material responds to a particular UV wavelength does not necessarily mean that the light source is the optimum choice for achieving the best possible result.

Film Positives, Emulsions and Screen Exposure Materials

The exposure light source is only one part of the screen-making process. A correctly exposed screen also requires a suitable photosensitive screen printing emulsion and a positive with sufficient optical density and image definition.

At Rittagraf, you can find materials for making your own screen printing positives, including inkjet and laser film, transparent polyester sheets, materials for hand-drawn positives and emulsions for different screen printing applications.

We also offer a professional film positive printing service, producing high-opacity positives using professional inkjet printing, dedicated inks for film positives and RIP software.

The Importance of Correct Exposure

Every combination of UV light source, emulsion, screen and film positive requires its own exposure conditions. Exposure times should therefore not be considered universal, and new tests should be carried out whenever the emulsion, light source or working setup changes.

Correct exposure helps ensure clean washout, good stencil durability and accurate reproduction of the original image.

Frequently Asked Questions

What is a screen printing exposure unit?

A screen printing exposure unit is a device used to expose a screen coated with photosensitive emulsion to UV light. The film positive selectively blocks the light, transferring the image to the emulsion so that the unexposed areas can subsequently be washed out to create the printable stencil.

Is a vacuum exposure unit better than a UV exposure lamp?

It depends on the application. UV lamps provide a simple solution for smaller formats and occasional screen making. A vacuum exposure unit provides greater control over the contact between the film positive and emulsion and makes the exposure process easier to reproduce consistently.

What size screen printing exposure unit do I need?

Consider both the internal printing area and the overall external dimensions of the screens you normally use. Each product specification indicates the exposure area and recommended screen size.

Do all exposure units use the same exposure time?

No. Exposure time varies according to the UV source and also depends on the emulsion, mesh, coating thickness, film positive and working conditions. When changing exposure unit, emulsion or setup, the correct exposure should be tested again.

Can a screen printing exposure unit be used for cyanotype or photopolymer plates?

It can be used with other photosensitive materials provided that their spectral sensitivity is compatible with the wavelength of the light source. Exposure times and working conditions need to be established specifically for each process.