Roger Baily contributed:
>
>Great, informative note. I always wondered how these coloured oxide films
>were created. Thanks, I will try your techniques.
>
>Have you, or others on the list, had any experience using caustic to
>chemically etch aluminum? We used to make hydrogen to fill party ballons
>and make mini hydrogen bombs by reacting aluminum foil with a caustic
>solution (Draino or lye) in a pop bottle. I often thought that this process
>could be used to etch masked aluminum surfaces to produce the base plate
>for a horizontal dial. I never did reduce the idea to practice as the
>hydrogen ballons and bombs were more fun. Were you more successful?
>
Roger and 'Watchers'
Etching with caustic soda is an interesting stage in an easy
form of multi-colour anodising - probably very relevant to dial making! Bill
Maddux recently suggested etched aluminium dial plates to me. Come to think of
it that is probably what jogged this current memory. Thanks Bill!
Stages.
1. Produce the anodic film.
2. Dye and seal.
3. Stick on self-adhesive paper shapes. Numerals? Lines etc.
4. Spray with auto paint aerosol.
5. Just as the paint is almost dry (critical) pick off the gummed shapes.
6. Place in caustic soda which will etch away the exposed coloured areas.
7. Re-anodise and re-dye a different colour through the 'hole' OR
8. Polish the exposed aluminium on a polishing wheel. The surrounding anodic
film is impervious to jewllers' rouge leaving mirror-bright lines/shapes on a
coloured background.
9. I discovered (or re-discovered) this process (and several others) by
experiment. Has anyone else trod a similar path?
Tony Moss
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