Rubylith® and Amberlith® Masking Films

rubylithrubylithRubylith (red in color) and Amberlith are masking films that are cut with an Exacto or similar knife to create an image on a clear backing sheet. The image is then exposed with a bright UV (white) light into a screen. The backing sheet and image are removed from the screen, and the screen is sprayed with water. The image washes out so that ink can pass through the image of the screen.

Amberlith allows more light to pass through than Rubylith, but both are very similar at blocking the UV spectrum.

Prior to computers Rubylith and Amberlith were the primary mediums for creating images, because they completely blocked the UV light. Masking films are still used to cover large areas very inexpensively. However, the process of hand cutting details in film products can be slow, imprecise and limited in the results that can be accomplished. Letters, for example, before computers were typically block style. Computers have allowed an explosion of fonts, stipple effects (images composed of dots), and other new graphics.

Capillary direct films (CDF) produced by the Ulano Corp. should be considered as an alternative to masking films. Today images are created in black either by 1) computer like MicroSoft Word or a graphics program like CoralDRAW or Adobe; 2) photocopy on to vellum; 3) drawing with black ink; and 4) rub off letters available from a stationary store. The image must be on a medium that allows light to pass through, except the image. Vellum is an example. CDF can be purchased for water based, plastisol or solvent based inks, and in different thicknesses to control the thickness of the ink deposit. CDF is used in schools, small screen printing shops and very technical screen printing applications.

Rubylith and Amberlith images can be combined with black images created by computer, photocopy, a black pen and transfer letters. Each type of image is laid over a screen coated with either a liquid emulsion or CDF capillary film. A masking film like Rubylith or Amberlith can be used to cover large areas easily and quickly with hard, sharp edges. So, for example, an image may be framed with a masking film.

Schools and shops without the Ulano Step Wedge Kit (exposure calculator) will find that over exposing screens with UV light produces great screens when using Rubylith and Amberlith. Vellum may produce a gray image in the vellum. Gray images allow light to pass through the image and when over exposed make wash out of emulsion from a screen difficult. Vellum can work successfully when the exact exposure time required is determined with the Step Wedge Kit and used.

Rubylith and Amberlith films are coated on a polyester backing sheet. The films include an adhesive to transfer the film to a clear sheet to create a positive. The film can also be transferred to negatives. Rubylith, not Amberlith, should be used on litho plates.

Typically art is taped down with the masking film taped over the art with the dull side of the film facing up. A light table will aid in seeing the art through the masking film. The image is cut without cutting through the backing sheet, and then the film that is not part of the image is peeled off. Each color of the design is cut out of a separate sheet of film laid over the art one color and sheet at a time. Fine details can be added to the backing sheet with pen and ink or an opaquing pen.

The uses of a masking film are limited only by your imagination. To avoid painting over large areas that would curl or warp, a film can be used. Customers have covered glass windows with Amberlith to protect light sensitive materials in labs and offices. Designs can be placed on a copy board with windows cut from masking films placed around the designs.

Amberlith has been discontinued by Ulano, and some forms of Rubylith have also been discontinued. However, some types of Rubylith are still available.

For more information, please contact Roger@screenprintingbiz.com.