Badly-damaged lamp for repair.
Remove excess brass powder gently with brush or silk ball. Take care not to break this surface powder coat. Place in moist box for ½ hr then repeat removal of excess brass dust and start polishing gently at the same time. Repeat this stage 2 or 3 times more at 1hr/2hr intervals, replacing in moist box each time.
Finally after settling in a safe place for 1 week, repair can be washed gently using soapy cool water.