Articles on the composition of 17th and 18th C clock brass?

NigelW

Registered User
Jan 2, 2015
455
44
28
London and Kent
Country
I am currently having difficulty finding a foundry I can trust to cast parts in the right colour brass. I have just received some casting from one firm which are far too pink, having been assured that they would look the same as "yellow clock brass". In reply to a (very polite in the circumstances) email in which I told them they were "too pink" he told me that in his many years in business he has never seen any brass come out pink before, so we have not made much progress.

Perceptions of yellowness and pinkness are far too subjective to have a meaningful conversation I feel. I need to talk technical - i.e. percentages of copper and zinc (and lead?), technical standards etc. There must be some articles out there on the subject. If anyone point me to one it would be most helpful.

On the right in the pic below is a wheel blank turned from cast yellow brass sheet (a good colour). On the left is a freshly filed casting, which to my eye is pinker (a bad colour) than the wheel blank. I have asked my caster for the technical specs of both types of brass. As he made the casting and sells cast yellow brass he should know both. I am awaiting his reply.

20191216_112856.jpg
 

novicetimekeeper

Registered User
Jul 26, 2015
10,949
876
113
Dorset
Country
Region
Robey did some articles on brass founders in London which are worth digging out.

One thing to know about brass in the period you describe is that there was no method available for producing molten zinc successfully as Zinc boils at a temperature lower than it can be reduced with charcoal meaning that elemental zinc was unavailable to them.

The method they used was to heat the zinc ore and the copper together so that the zinc vapour would permeate the copper. The copper could then be melted down to get a consistent alloy.
 

NigelW

Registered User
Jan 2, 2015
455
44
28
London and Kent
Country
I have just spoken to the supplier of the cast yellow brass sheet I used to make the wheel blank. He tells me it was 60% copper, 2.7% lead and the remainder zinc. He also recommended a caster in Devon whom I had separately identified someone who could make my castings.
 

NigelW

Registered User
Jan 2, 2015
455
44
28
London and Kent
Country
Robey did some articles on brass founders in London which are worth digging out.

One thing to know about brass in the period you describe is that there was no method available for producing molten zinc successfully as Zinc boils at a temperature lower than it can be reduced with charcoal meaning that elemental zinc was unavailable to them.

The method they used was to heat the zinc ore and the copper together so that the zinc vapour would permeate the copper. The copper could then be melted down to get a consistent alloy.
Most interesting. I found this while searching for articles by Robey (his pamphlet for the British Museum on ferrous metallurgy in clocks is available but at a very fancy price):
http://www.bhioxbranch.co.uk/mans_early_use_of_metals.pdf
 

Ralph

NAWCC Member
Sponsor
Jan 22, 2002
5,176
277
83
Country
If I remember right, Roger White's Lantern Clock Book had some analysis of early brass.

Ralph
 

Forum statistics

Threads
165,521
Messages
1,440,928
Members
86,278
Latest member
GeorgeSlari
Encyclopedia Pages
1,101
Total wiki contributions
2,873
Last edit
Weekly News 7/7/19 by Tom McIntyre