Wednesday, February 1, 2012

Fun in the kitchen

 While waiting for milling cutters I took up an old skill. It is about 5 years since I made the last photoetched part for miniatures.

I found some good photos of realsisize Queen Anne style brass pulls and escutcheons to be used on the "Bonnet-Top High Chest"

Real size is 3 1/8 inch across that gives 1.65mm in scale 1/48. A few details have to be left out :-) 
A little work with a drawing program the photos is transformed into a black-and-white photomask.

Below is the testprint of a lot of the brasses and the resulting photo-mask scaled down to 1/48 scale.

Then to the kitchen because running water is a must.

First cleaning a piece of 0.1mm brass sheet.

 Then adding a photosensitive film to both sides of the brass sheet.

There are two ways of using this film; either dry or wet. The dry process requires a laminating machine with great pressure from the rollers. I don't have one.

The wet process can easily be used in the amateurs workshop and there is very little difference in the next steps. The photosensitiive film is protected by a thin plastic on both sides.  One of the plastic layers is removed and the brassplate is submerged in cold water and the unprotected film is then placed on the brass plate. The assembly is then taken out of the water and the water and airbubbles is squeezed out so te film adherers to the brass. After short drying eventually with the help of a hairdrier the plate is ready for exposure.

Exposure requires ultraviolet (UV) light en mass. My UV source has four UV tubes and is controlled by an old dark-room timer. 

After a few tests for checking sensitivity of the film and blackness of the photo-mask I got this. Exposuretime 30 seconds.  The film turns light blue when exposed to UV. Developing the film is done in a light solution of soda ash. (10grams to 1liter of water)

 Ready for the etch.

Etching is done in a strong solution of ferri chloride. A nasty stuff. Leaves brown marks everywhere if not removed immediately but it is one of the best solutions for etching copper and brass.

In my etching tank there is an aquarium heater to raise the temperature to about 30deg.celcius and an aquarium pump supplies some air bubbles to circulate the solution. That makes the etchiong process go faster. I forgot a photo of the etching tank and now the kitchen is cleaned up :-)

Result of todays work.
Better than expected.
I stopped etching with a little bit of brass left (to the left :-)

And a little closer.

The brass is still hidden under the photo-film. I'll strip off the film and polish the brass when I am ready to mount them.  Stripping the film can be done with either a strong solution of soda ash (1cup to 1liter of water) or with acetone.

Todays etch was a little experiment too because I etched from one side only. That way I didn't have to make two films and have them lined up before exposure. Also I didn't need tabs for holding the parts from falling off and then dissappearing in the etching solution.

Have fun


  1. Thanks Niels, I didn't realize one can do this at home, something new to think about and try!!!

  2. So all that is left outside of the masked parts is the film from the other side? How cool is that!!! very exciting.