PROJECT 13
January 2003 - August 2004
RESTORING A 1929 MECCANO STEAM ENGINE
Manufacturing cover 2
Next I had to hammer down the lip to finish off. I hammered on a long socket extension to
reach into the tube. I slipped the boiler cover over a broom stick handle and hammered down
the lip from the other side as well.
Note the protective cover that came with the brass sheet.
Next I need to oxidize the brass. I did a bit of investigation on the internet and found that you can
darken brass using a number of chemicals :
- Commercial brass darkening solutions
- Ferric nitrate (Light to Dark)
- Sulfurated potash (Brown to black)
- Ammonia (NH3).
The ammonia is not as predictable, but is the cheapest. The unfinished bronze is a bright light gold color,
After treating it will turn a dark brown like the chimney. The trick will be to get the shades to match.
I bought some household bleach (Scrubb's cloudy ammonia). The label stated that it contains 8% m/m Ammonia (NH3).
I don't understand the chemistry behind it all, but maybe different concentrations of ammonia will give different shades?
My result was a blackish / bluish almost brownish finish.
I was not ecstatic with the result, but I gave it a light polish with Brasso and the blue went away.
One thing to note : My research noted that you can only darken natural brass. You should clean the brass with Acetone to
remove any lacquer, dirt, oils etc. I did not do this and my result was slightly blotchy due to residue oils from the protective
film that came with the brass.
The outer boiler cover before dipping into Ammonia (NH3).
The outer boiler cover after dipping into Ammonia (NH3).
The bluish tinge and white residue went away with a very light Brasso polishing.