This article provides detailed instructions for both file preparation techniques and the special inks processing options available in CalderaRIP.
Good to know
While most documentation focuses on "white" ink as a common example, the processes described apply to a variety of special inks, including fluorescent, primer, varnish, gloss, clear, silver, and metallic. When using an ink other than white, ensure that you prepare your file and name the spot color(s) accordingly.
If your printer is equipped with multiple special inks (e.g., White and Varnish), additional tabs will appear in the Page Setup for each ink. There is no special interaction between these inks; you can enable one while disabling another and select different methods (e.g., Contour filling for White and Spot for Varnish). However, it is important to note that the same spot cannot be used for two different inks.
Scenario 1: Pre-prepared file
Spot Color
After preparing your file in an image processing application (e.g., Photoshop), you can import it and print it with CalderaRIP by choosing "Use a Spot Color" as the color separation method.
This is the most powerful yet complex method. It requires the PS/PDF interpreter to create an additional separation (in addition to the standard C, M, Y, K separations) that contains only the white data for all objects assigned to a chosen spot color (typically "White").
Careful preparation of white (or other special inks) objects in the design application is essential, as it can involve overprinting.
You may be interested in reading:
- How to create a spot color with or without overprint in Adobe Illustrator? (Includes how to import and print)
- How to create a Spot Color in CorelDRAW? (Includes how to import)
- Separation method: "Use a Spot Color"
Extra-Channel
After preparing your file in an image processing application (e.g., Photoshop), you can import it and print it with CalderaRIP by using the "Use an extra channel" color separation method.
This method utilizes an extra channel (or alpha channel) in a raster image, typically in TIFF format, to create a white separation. While this method is straightforward, it has limitations in quality, as it does not support vector elements or text.
You may be interested in reading:
- How to create an extra/alpha channel in Adobe Photoshop? (Includes how to import and print)
-
How to manage extra channels when importing a file with FileMan?
Info
The FileMan option "forces" the alpha channels of files to be assigned to the selected spot channel (such as white). This is particularly useful for saving time, as it allows the Automatic separation method (Print module > Page Setup > Spot ink tab) to function without requiring further setup.
- Separation method: "Use an Extra Channel"
Contour Filling / Cut contours
After preparing your file in a vector application like Adobe Illustrator, similar to contour cutting workflows, you can import it and print it with CalderaRIP by using the "Fill a contour" color separation method.
Contour filling involves using vector contours in a PS/PDF file to create special color separations, such as white, varnish, or metallic finishes.
Although contour filling has limitations, such as fixed color density within the contours, it can be a simpler alternative to creating spot colors.
You may be interested in reading:
- How to create a Cut Contour in Adobe Illustrator? (Includes how to import and print)
- How to create a Cut Contour in CorelDRAW? (Includes how to import)
- Separation method: "Fill a Contour"
Scenario 2: File not prepared
CalderaRIP offers several options to process special inks that do not require any special file preparation and are compatible with both raster and vector files. However, these options might be limited to specific scenarios (suitable for experimentation or demonstration purposes).
These non-preparation methods are not activated automatically; you must specifically select them in the White tab (or other special ink tab) of the Print module > Page setup.
Generate from CMYK data
This method generates special ink percentages based on the underlying CMYK density. For this method, set the following computation parameters:
In this computation, the white channel is filled for all pixels where the underlying CMYK data is not zero:
The algorithm is applied before screening. For example, if a shape is filled with 1% yellow, it will receive the same amount of white ink as if it were filled with 100% black.
This approach differs from simply applying a dot of white ink wherever there is an existing dot of any other ink, which may be an option available directly on the printer controller.
This computation operates in contrast to the previous one. It fills the areas of the print that are intended to be white with white ink.
This computation is a more sophisticated version of the previous two. It allows for the adjustment of white ink quantity based on the amount of underlying ink.
Specifically, you will set up a "transfer function" that serves as a look-up table. For each pixel, the total quantity of ink is computed, and the transfer function is used to determine the percentage of white ink to apply:
This transfer function is applied before linearizing the CMYK data. As a result, the same transfer functions can be utilized across different resolutions and printers, yielding consistent results.
You may be interested in reading:
Full Page Coverage
This method is straightforward: the white ink will be uniformly applied across the entire page, filled with a background of the specified density.
You may be interested in reading:
Old documentation on the topic
GrandWhite user guide (2011, for historical purposes)