Posted on 01/11/2012 10:48:04 PM PST by SWAMPSNIPER
RegulatorCountry gave you a comprehensive answer.
The short answer is amberlith was/is an amber colored film that was transparent to the eye but blocked the covered area from appearing on the photo film used to prepare printing plates. Used most often on back light tables that helped the cutter see the source art or photo better.
It was a large step up from using a brush and photo opaque ink for block out work, especially when large areas needed covering. Opaque ink work always had the problem of flaking off, leaving pinholes which showed up as black spots or blotches on the finished product. And you couldn't see the underlying source to make sure parts of the desired object weren't covered.
Like RegulatorCountry I was always looking for new techniques and technology to help me work faster and better. I started as a draftsman using wooden pencils, ruling pens and leroy pens drawing on drafting linen. Thank goodness for computers and software.
Thank you for the detailed explanation.
My experience (very limited) with physical typography and page layout was limited to pasting up strips of Linotype-set copy with hot wax on a light table, with a special “point marked” ruler.
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