When it comes to screen printing separations, spot color is king. As this article covers, popular techniques include spot color, CMYK, simulated process and index. But spot color shines for its simplicity and accuracy.It works by separating each color into its own layer with an individual screen and ink. This prevents overlapping and intermingling, allowing flawless control and registration across diverse prints.
Introduction: Colour separation is a vital process in screen printing, essential for achieving high-quality, detailed, and vibrant multicolour prints. This guide delves into different colour separation techniques, offering insights into their suitability for various design requirements.
Spot Colour Separation in Screen Printing
- Application: Ideal for designs with solid, distinct colours.
- Common Uses: Best for printing texts, logos, line art, and graphics with clear, defined edges.
- Software Tools: Typically executed in vector graphics programs, notably CorelDraw [1] and Adobe Illustrator [2].
- Strengths: Renowned for its high colour accuracy and vibrancy, ensuring crisp and bright prints.
- Limitations: Not the best choice for designs with gradients or numerous colours. Less effective for photorealistic images due to its focus on single, solid colours.
CMYK Color Separation in Screen Printing
- Ideal For: Photorealistic images requiring a full colour spectrum.
- Process: Utilizes Cyan, Magenta, Yellow, and Black inks. Employs halftone dots at various angles to layer colours, forming detailed, multi-hued images.
- Best Used On: White or pale backgrounds. Ink transparency affects colour vibrancy on darker materials.
- Advanced Techniques: Printing on dark fabrics achievable with additional skills and a white underbase screen.
- Technical Tip: Maintain consistent squeegee pressure to ensure even colour distribution.
- Resolution Recommendation: 300 DPI for optimal print clarity.
- Dot Shape Note: While round dots are standard, oval dots can enhance screen development, particularly in complex images.
Simulated Color Separation in Screen Printing
- Technique Differentiation: Utilizes opaque inks, often exceeding the traditional four-colour CMYK palette.
- Dot Technique: Employs a method of placing adjacent and overlapping dots of different colours, enhancing the depth and detail of images.
- Squeegee Pressure Sensitivity: Less affected by squeegee pressure variations compared to CMYK, allowing for more consistent prints.
- Suitability: Ideal for darker garments, capable of reproducing a wide colour range and detailed designs.
- Screen Requirements: Typically requires more screens than CMYK to achieve the full spectrum of colours and details.
- Resolution Recommendation: Optimal results achieved with artwork at 300 DPI, ensuring clarity and detail in prints.
- Ink Preference: Uses opaque inks, particularly effective on dark background colours.
And here is how to do it in Photoshop
Index Colour Separation
- Technique Overview: Transforms images into a pattern of square dots, each representing a different colour, suitable for intricate patterns and full-area prints.
- Dot Arrangement: Features a precise, non-overlapping layout of square dots, arranged to mimic the original image using a limited palette.
- Screen Demand: Often requires more screens than other methods, particularly for designs with numerous colours or complex gradients.
- Design Suitability: While simpler to execute than some methods, it’s ideal for designs where maintaining exact colour placement is crucial.
- Print Quality: Can result in a pixelated look, especially in subtle transitions. Using a DPI range of 150-225 DPI can enhance print smoothness and detail.
- Resolution Tips: Optimal separation resolution is between 150 to 200 DPI for balance between detail and clarity.
The importance of image quality
Regarding the quality of the separation, here a Quote
Garbage in, Garbage out
Scott Fresener ( Writer of “How to Print T-Shirts for Fun and Profit”) [3]
You need an image of the best quality and high resolution. Poor image quality leads to poor film separation = poor prints.
Separation example for download
Here is a sample of a Simulatet process colour separation that I did for a customer. If you want to try it out, just download the colour separation and print out the film. The important thing is to use the screens as described on the film. The magenta colour on the picture has been changed by text and border. It is important that you can hold the small dots on your screen.
- Monster Seps Film UNDERBASE ( Mesh T-90 )
- Monster Seps Film BLACK ( Mesh T-90 )
- Monster Seps Film COOL GRAY 7 ( Mesh T-90 )
- Monster Seps Film WHITE ( Mesh T-90 )
- Monster Seps Film GREEN 375 ( Mesh T-90 )
- Monster Seps Film GREEN 355 ( Mesh T-120 )
- Monster Seps Film YELLOU 35 ( Mesh T-120 )
Choosing Your Screen Printing Separation
| Category | Spot Colour | CMYK Process | Simulated Process | Index Colour |
| Primary Use | Suitable for solid, vibrant colours; ideal for logos and simple graphics. | Best for full-colour images, mainly on light fabrics; not ideal for dark fabrics. | Perfect for detailed, colourful images on dark garments; effective on light fabrics too. | Great for both light and dark fabrics; excels with complex colour patterns and gradients. |
| Characteristics | Delivers vivid, crisp prints; mostly used for simpler designs. | Generally less vibrant; can be enhanced with extra spot colours. | Yields vibrant prints using overprinted opaque inks; known for smooth transitions and detail. | Produces detailed, complex images; may result in a slightly textured appearance. |
| Technical Demands | Simple technique, great for beginners. | Requires precise screen alignment and expert colour separation. | Demands advanced colour separation and screen preparation for detailed imagery. | Needs precise colour separation; screen printing process is more forgiving. |
| Separation Complexity | Relatively easy to print. | Enhanced with additional spot colours. | More complex than Index Colour but generally simpler than CMYK. | Typically requires more colours, especially for dark fabrics. |
| Colour Dynamics | Excellent colour accuracy. | May need adjustments for desired vibrancy. | Bright, vivid output, especially over a white underbase. | Distinct dot pattern can affect colour texture. |
| Screen & Material | Uses a limited number of screens. | Employs four main screens; requires careful placement. | Often needs multiple screens for depth and richness. | Demands numerous screens for the fixed palette. |
| Fabric Compatibility | Works well with various fabric colours. | Optimal for light-coloured fabrics. | Effective on both light and dark fabrics; uses underbase for darks. | Adaptable to light and dark fabrics alike. |
| Skill Level & Learning | Ideal for beginners in screen printing. | Requires understanding of colour and screen setup. | Needs proficiency in screen preparation and ink management. | Printing is straightforward, but high-quality separations need skill. |
Questions & Anwsers
How to separate colours for screen printing
For raster images like photos, use a pixel program like Adobe Photoshop. For vector graphics like logos, CorelDraw or Adobe Illustrator is suitable. Special plugins and standalone programs can also aid in colour separation for both types of images.
What type of colour separation is used for Sepia Tone Separation in screen printing?
For Sepia Tone Separation of photographic images in screen printing, Simulated Process Colour Separation is used. This method involves converting the image into grayscale and then using a range of specific colours in the simulated process to achieve the sepia effect. It allows for detailed reproduction of the photograph with the characteristic warm, brownish tones of sepia.
What type of colour separation is used for grayscale images in screen printing?
For grayscale images, screen printing can use either Simulated Process or Index Separation. Simulated Process is ideal for smooth gradients and detailed shades, using halftone dots. Index Separation, with its pattern of square dots, is suitable for achieving certain stylistic effects. The choice between them depends on the specific design requirements and the desired visual outcome of the print.
Personal Conclusion:
Spot color printing represents the foundation of screen printing, serving as the essential starting point for every screen printer. Its relatively low-tech approach makes Spot Color Separation the ideal entry into the craft, perfect for designs featuring solid, distinct colors without gradients.
However, when a design incorporates gradients or subtle transitions, I recommend beginning with Index Color Separation. This technique demands a higher skill level than Spot Color Printing but offers a bridge to more complex separations, allowing for nuanced detail within limited color palettes.
As your experience and mastery of screen printing variables grow, you can then venture into Simulated Process and CMYK separations. It’s worth noting that CMYK printing, with its sensitivity to pressure variations, often necessitates the use of an automatic printing machine to achieve consistent, high-quality results.
In every screen printer’s journey, there’s a progression from simple to complex, a path that challenges us to expand our skills and embrace the nuances of our craft. Remember, every expert was once a beginner. Happy color separation and printing! Never forget that we all started small, and each step forward is a step towards mastery.
Should you have any questions or wish to add your insights to this article, I warmly invite you to share your thoughts in the comments. Let’s continue learning from each other and pushing the boundaries of what’s possible in screen printing.
Happy printing,
Stefan Mertes
