RussellT
Established Member
I thought I would post this, because I tried it and I thought it was a really useful technique with results way better than I expected.
I retrieved some old household scales from my mother in law's shed and I thought I would restore them. Cleaning the rust off and painting was quite straightforward but the dial, which was painted steel was beyond saving. I decided to make new dial from brass.
I drew a new dial on the computer, and printed it out on an overhead projector transparency.
I bought some "Photosensitive Dry Film for Circuit Production" and attached it to a sheet of brass by putting it through a laminator.
I sandwiched my printout between a sheet of glass and the brass sheet with the photosensitive film and exposed it to UV light. It can be done with sunlight but I found I needed to experiment with exposure times so used some UV diodes.
Then I washed it with a dilute washing soda solution (a couple of teaspoons of washing sodas in 500ml of water) and that removes the unexposed area of the photosensitive film. If it doesn't come off easily then it might have been over exposed (Guess how I know that).
Then I etched it with Ferric Chloride. Other etches are available but Ferric Chloride isn't particularly hazardous unless you're made of metal. I checked it at intervals because if you etch too deep then it will undercut the edges of the photoresist film and it loses definition.
Then I washed it again with a strong solution of washing soda and removed all the film.
I sprayed it with black car paint and then rubbed the paint down with 1200 grit wet and dry and polished it with metal polish leaving the paint in the areas that had been etched.
I cut the sheet to size with shears and filed the edge to the line and drilled and filed the holes.
Hera are some photos, showing the scales as finished and the original dial.
Russell
I retrieved some old household scales from my mother in law's shed and I thought I would restore them. Cleaning the rust off and painting was quite straightforward but the dial, which was painted steel was beyond saving. I decided to make new dial from brass.
I drew a new dial on the computer, and printed it out on an overhead projector transparency.
I bought some "Photosensitive Dry Film for Circuit Production" and attached it to a sheet of brass by putting it through a laminator.
I sandwiched my printout between a sheet of glass and the brass sheet with the photosensitive film and exposed it to UV light. It can be done with sunlight but I found I needed to experiment with exposure times so used some UV diodes.
Then I washed it with a dilute washing soda solution (a couple of teaspoons of washing sodas in 500ml of water) and that removes the unexposed area of the photosensitive film. If it doesn't come off easily then it might have been over exposed (Guess how I know that).
Then I etched it with Ferric Chloride. Other etches are available but Ferric Chloride isn't particularly hazardous unless you're made of metal. I checked it at intervals because if you etch too deep then it will undercut the edges of the photoresist film and it loses definition.
Then I washed it again with a strong solution of washing soda and removed all the film.
I sprayed it with black car paint and then rubbed the paint down with 1200 grit wet and dry and polished it with metal polish leaving the paint in the areas that had been etched.
I cut the sheet to size with shears and filed the edge to the line and drilled and filed the holes.
Hera are some photos, showing the scales as finished and the original dial.
Russell
