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emeritus · 5th Dec 2019, 5:48 pm

The 1942 edition of "Machinery's Handbook" has a couple of pages on colo(u)ring brass in a variety of colours. There are several for black, but the only one that does not involve the use of Cyanide and/or Arsenic is as follows:

" Another cheap solution is composed of 8 ounces of sugar of lead, 8 ounces of hyposulphite of soda and 1 gallon of water. This must also be used hot and the work afterwards lacquered to prevent fading. When immersed, the brass first turns yellow, then blue and then black, the latter being a deposit of sulphide of lead".

Being an American book, the "gallon" would be the US gallon of about 128 fluid Oz, rather than the UK gallon of 160 Fl. Oz. No indication as to how hot is "hot". Lacquering is also recommended for all but one of the other processes

5th Dec 2019, 5:48 pm	#14
emeritus Dekatron Join Date: Jan 2012 Location: Brentwood, Essex, UK. Posts: 5,337	Re: Black oxide coating on brass The 1942 edition of "Machinery's Handbook" has a couple of pages on colo(u)ring brass in a variety of colours. There are several for black, but the only one that does not involve the use of Cyanide and/or Arsenic is as follows: " Another cheap solution is composed of 8 ounces of sugar of lead, 8 ounces of hyposulphite of soda and 1 gallon of water. This must also be used hot and the work afterwards lacquered to prevent fading. When immersed, the brass first turns yellow, then blue and then black, the latter being a deposit of sulphide of lead". Being an American book, the "gallon" would be the US gallon of about 128 fluid Oz, rather than the UK gallon of 160 Fl. Oz. No indication as to how hot is "hot". Lacquering is also recommended for all but one of the other processes Last edited by emeritus; 5th Dec 2019 at 5:54 pm.