Casting with yellow brass

Just had a reply from my caster:

"I have never seen it come out pink before and i have been doing this a very long time. The only time you get a pink colour is silver solder flux will turn it pink but this comes off when the flux is cleaned off. A pink colour is the colour of Bronze and not the dark brown that people think of Bronze we do not cast much of that. Lost wax brass is just a less yellow colour we can sand cast the clockmakers yellow brass but as i said it gives off a lot of fumes so we cast that when we have enough orders to make up a load and do it in the evening when everyone has gone home the smoke that comes out is unbelievable. If you wanted to do that we would need patterns 4% larger and the casting would need a lot more work and may have some gas holes in it."

I once had a complete 400 day clock movement turn pink after leaving the parts for too long in an amonia based cleaning solution, apparently it reacts with the zinc somehow.

Phil

I have asked my caster to provide me with a specification of the brass he used and that of the yellow clock brass so that I can understand the differences and talk specifics rather than generalities. He seems to have failed to understand the point that there is a spectrum of colour for different brass alloys, with those higher in copper being pinker and those higher in zinc being yellower. Fastidious clock restorers only want the yellower brass.

This, incidentally, is the unrestored backplate of my clock, showing all the vacant holes where the missing mechanism would have been. Using pink brass on this would stick out like a sore thumb.

I am using a CAD programme to design the missing parts and ensure that they fit with the original plates.

Which CAD program are you using, my day job is Chief Mechanical Design Engineer and we use Solidworks 3D, so I have the bonus of being able to use it for my hobbies as well.

Phil

.

Recommended reading for your caster: **LINK**

http://copperalliance.org.uk/uploads//2018/03/pub-117-the-brasses_whole_web-pdf.pdf

MichaelG.

.

P.S. ... Lovely looking clock : Stick by your principles !!

I am using Fusion 360, which I can use for free as a hobbyist. It is a little slow on my rather antique iMac and very occasionally gets stuck but I have found it exceptionally useful. i am told Solidworks is the bees' knees!

Here is an example of my work on it.  Most of the parts shown are ones I need to make to replace the missing mechanism.

Edited By Nigel Watts on 19/12/2019 08:53:53

I think I finally might be getting somewhere. I phoned another supplier from whom I have in the past bought cast yellow brass of a good colour. He tells me the composition was 60% copper 2.7% lead and the rest zinc. He also mentioned the name of a caster in Devon whom I had separately identified as a possible candidate to cast my parts.

I feel some sympathy for the foundry, who is used to working with modern materials and methods. Your requirement is a tricky one.

When the clock was made in 1710 Brass wasn't made to a specification at all. Although Zinc was known to be a metal, it wasn't isolated until 1746. Early brass is a pot-luck product.

Brass making in 1710 involved mining Calamine (later identified as Zinc Carbonate) which occurs in association with Lead and Silver ores, mainly Galena. The mixed ores went through several crude processes intended to concentrate and separate the ores from impurities such as earth, stones and calcite. Lead and Silver aren't too difficult to extract because they melt and pour at reasonable temperatures. Zinc is much harder to separate because it vapourises and oxidizes at low temperatures; melts at 420C, boils at 907C. The vapour and oxide are both toxic.

In this period Brass was made by mixing concentrated Zinc Ore with molten Copper. By modern standards the Copper was impure, perhaps as low as 80%, and the actual content of the Zinc Ore varied from batch to batch. As they weren't adding zinc metal, it was hard to judge how much zinc was in the mix. On top of that, it was difficult to control the temperature of the furnace - slightly too hot and the Zinc would boil off. Skilled work with erratic results. Although Brass makers aimed for a high-zinc yellow brass, their output was highly variable. Brass made in 1710 is likely to contain Gold, Silver, Lead and many other impurities not found in modern metal. Old clock brass is unlikely to match any standard brass made today, because modern brass (after 1870) is made to a specification.

As British brass making was in it's infancy in 1710, it's likely this clock was made from imported brass. At that date the best brass came from Germany.

Although an exact match of colour and properties is unlikely, there's no reason why a modern high-zinc brass wouldn't be acceptable. But the requirement may be a tad more specialised than your foundry is placed to deal with, rather as Argos don't sell Rolex Watches! One problem is the fumes, the other is melting and casting a very high-zinc brass is somewhat out-of-the-ordinary. As clock restoration is a fairly common activity, it may be a matter of finding which foundry does this sort of work. It may not be easy, and it may be worth persisting with your choice who is at least trying to be helpful. Not so my nearest foundry who are high-tech, mainly aero-space. No problem if I want several tons of centrifugal castings made from almost any metal I care to name, but they're absolutely not interested in low quantity low value work. When I was a lad there were several jobbing foundries nearby, now I've not found anyone within a 50 mile radius remotely interested in doing a few simple castings. For small quantities, DIY may be the best approach -not impossible, as described by Neil.

Very impressed by what you're doing, both with the real clock and the Fusion 360 model. Hope it comes good without compromising authenticity.

Dave

Looking at the amount of effort and thought that has gone into your 3D model, I can fully appreciate that you have every intention of seeing this restoration through to a satisfactory end.

I for one will be following your progress with interest, please keep giving us updates and some more photo's as you get parts made

Phil

Any decent scrap yard would point their zapper at that clock and give you the exact composition in moments. I don't know if this would be helpful but it at least would be cheap.

old plumbing fittings give a good yellow brass !

I have been posting a kind on blog on my effort here, if you are interested:

https://mb.nawcc.org/threads/1710-etherington-table-clock-with-lots-of-bits-missing.158249/

Edited By Nigel Watts on 20/12/2019 09:36:27

Thanks for the link, Nigel

I shall be following your adventures with great interest.

MichaelG.

Are you sure? If that's the case we had better warn the millions of people poisoning their babies with Sudocrem...

Neil

.

This may be of interest: **LINK**

https://www.azom.com/article.aspx?ArticleID=6477

Not a match, but getting close ... and it’s an actual modern specification.

MichaelG.

.

Edit: and there are other specs. listed:

https://www.azom.com/search.aspx?q=Leaded%20Yellow%20Brass&site=all&fsb=1

Edited By Michael Gilligan on 20/12/2019 22:50:36