What causes irregular shaped bars?

[MinerJim]

I’m interested in finding out what causes lumps & bumps as well as the lines on the bottom of the Umicore bar I recently picked up. I actually like the irregularities, just curious in the process of making these bars and what can affect the casting process, as they all seem a bit different! This bar had bulges on the top, presumably causing the edges of the letter punch to be visible? It’s also has a curved bottom ? Thanks in advance if you can shed some light on the process or have any good YouTube links etc! 

[James32]

Simply the cooling/pouring process. Mould could be too cold..pour could be too aggressive. That bar above is the worst I've ever seen though.

[James32]

Will tag a few better in the know.

@BackyardBullion @LiquidMetalsUK @RiverbankSilver @SilverAngel

[Sovhead]

It’s a strange base, you’d think any kind of pour would still have a flat base esp considering what James says about re the temp of the mould etc.

Be interesting to hear what the experts on here say 👍🏻

 

Edited January 30 by Sovhead

[LiquidMetalsUK]

That bar pictured has been crushed before packaging causing the dents in the bottom and the indents in the top also the curve is a dead give away . Seen a few like that over the years 

Edited January 30 by LiquidMetalsUK

[SilverDrum]

3 minutes ago, LiquidMetalsUK said:

That bar pictured has been crushed before packaging causing the dents in the bottom and the indents in the top also the curve is a dead give away . Seen a few like that over the years 

It's a wonder. Could have been damaged whilst it was still hot perhaps? Surely it would be hard to dent so significantly once hardened.  

[Jake0111]

They looks to be some marks from the casting process but its more than lightly from crushing, like stated above. 

Casting into a mould will always give a consistent shape unless you have got areas that havent filled. You can get slight warping from the metal cooling but not as bad as that bar is.

[Sovhead]

6 minutes ago, LiquidMetalsUK said:

That bar pictured has been crushed before packaging causing the dents in the bottom and the indents in the top also the curve is a dead give away . Seen a few like that over the years 

Piles on pallets in the factory guy a bit sharp on the forklift catastrophe and they’ve just packaged them up 🤷‍♂️

[LiquidMetalsUK]

Just now, Sovhead said:

Piles on pallets in the factory guy a bit sharp on the forklift catastrophe and they’ve just packaged them up 🤷‍♂️

Exactly that bud 

[Sovhead]

Just now, LiquidMetalsUK said:

Exactly that bud 

I said that because the bottom of the bar has an indentation the thickness of a bar 

[Jake0111]

2 minutes ago, Sovhead said:

Piles on pallets in the factory guy a bit sharp on the forklift catastrophe and they’ve just packaged them up 🤷‍♂️

I would have thought it had happened after the plastic rapper was put on. 

[Sovhead]

Just now, Jake0111 said:

I would have thought it had happened after the plastic rapper was put on. 

Surely the plastic would have been marked though with such pressure?

[Jake0111]

Just now, Sovhead said:

Surely the plastic would have been marked though with such pressure?

Be surprised how much the plastic can take if its a blunt object putting the pressure on. 

[SilverDrum]

Just now, Sovhead said:

Surely the plastic would have been marked though with such pressure?

I thought the same with the stamping. None of that looks to be flattened. So looks to be damaged before that process also. 

[MinerJim]

Interesting comment about being crushed, hadn’t thought of that but now you mention it it makes sense 

[Sovhead]

2 minutes ago, SilverDrum said:

I thought the same with the stamping. None of that looks to be flattened. So looks to be damaged before that process also. 

It still weighs a kilo they’ve wrapped it sent it saves them money re melting and pouring again.

[sixgun]

This Umicore bar is a cast bar - so there won't be the cooling lines one might see with a poured bar.

A measured weight of silver shot in put into a mould and then the moulds are put into a furnace. The silver melts and runs out to fill the mould. You can get exact weights on these bars which aren't possible with a hand poured bar, unless you are really lucky.

The mould will be smooth sided and regular. They are machine cut in graphite. The bottom of the bar should come out of the mould with a flat bottom - we can see in image 4 the bottom is slightly curved. The bar has been bent but the mould will be straight and flat. We also see the significant transverse indentations in image 2.

Could the bar have had something really heavy deforming it whilst it was still hot after coming out of the mould? i haven't see Umicore bars made so i don't know what the exact process is but i would expect these deformities have occur to the bar after it has come out of the mould.

[sixgun]

This video shows a 250g Umicore cast bar - we can see a horizontal ding on one edge of the bar - looks like an after casting mark

 

Here Salivating Silver talks about cast and poured bars

 

[Jake0111]

25 minutes ago, sixgun said:

This Umicore bar is a cast bar - so there won't be the cooling lines one might see with a poured bar.

A measured weight of silver shot in put into a mould and then the moulds are put into a furnace. The silver melts and runs out to fill the mould. You can get exact weights on these bars which aren't possible with a hand poured bar, unless you are really lucky.

The mould will be smooth sided and regular. They are machine cut in graphite. The bottom of the bar should come out of the mould with a flat bottom - we can see in image 4 the bottom is slightly curved. The bar has been bent but the mould will be straight and flat. We also see the significant transverse indentations in image 2.

Could the bar have had something really heavy deforming it whilst it was still hot after coming out of the mould? i haven't see Umicore bars made so i don't know what the exact process is but i would expect these deformities have occur to the bar after it has come out of the mould.

You can get lines in a cast bar becuse you can get cold over lap if your pouring to slow.

[sixgun]

How does this work when there is no pouring with a cast bar? The silver shot in the mould melts en masse which means you get more uniformity. Agreed if you are not speedy about a poured bar you will get lines and layers as the silver solidifies whilst other parts are still liquid.

[Jake0111]

1 hour ago, sixgun said:

How does this work when there is no pouring with a cast bar? The silver shot in the mould melts en masse which means you get more uniformity. Agreed if you are not speedy about a poured bar you will get lines and layers as the silver solidifies whilst other parts are still liquid.

You still have to pour the metal with any type of cast unless you are Vacuum Casting or other specialist casting methods like the cosworth process (was made specially for the cosworth engine blocks) and i dont think any one casting gold or silver would do that. 

You dont melt the silver shot in the mould, it would kill the mould.

Even large scale foundrys only use a mould one time and make a new one in most applications, even with continuous casting. I know you dont need to do that with gold and silver normally becuse you dont put enough stress on the moulds for it to warrant it normally. 

[sixgun]

Here is my pal Jim Forsythe and his outfit.

The clip starts with them making cast bars.

 

[sixgun]

Argenta - members have sold bars from these people

 

Here we see Baird casting bars

 

Edited February 1 by sixgun

[Jake0111]

5 hours ago, sixgun said:

Argenta - members have sold bars from these people

 

Here we see Baird casting bars

 

Learn something new every day, but i wouldn't say that is a tradition casting process or if it could be called that. The mould has been made part of the furnace, but still interesting. You would end up with a better gold/ silver bar than casting one with that method.