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Forging, annealing, rolling ingots


#1

Hello.

I have been searching the archives, and have learned a lot about the topics of pouring, forging, annealing, and rolling ingots.

I am still unclear about a few things and have two questions to ask, if I may:

1- After pouring an ingot, is it recommended to anneal before forging it?

(I understand that I should anneal after forging, and before (and during) rolling,…)

2- during the rolling process, it is recommended to anneal often…but I also read that it is best not to anneal too quickly…but rather, to roll to about a 50% reduction before annealing…(that if you anneal too soon, you are not compressing evenly through/ deep into the metal?)…I was just wondering if the definition of “annealing often” meant the same/ similar to “after about a 50% or so reduction”?

I have the two recommended books below in my Amazon shopping cart, but will have to wait a bit before I can purchase them, so I thought I would ask these questions here.

Mark Grimwade’s book "Introduction To Precious Metals"
Dr. Erhard Brephol’s “Theory and Practice of Goldsmithing”

Thanks in advance!
Julie


#2

You are likely to get conflicting advice. For instance, when casting ingots, one person will tell you to thoroughly clean all oil and grease from your ingot mold, another will tell you to oil it thoroughly before using it. Both get good results, so try both. Whatever works for you is the right way to do it.

Assuming the ingot is cast properly, the way I approach annealing and forging / rolling is to forge the ingot on all sides hard enough to deform it, then roll it just enough to straighten it out, then anneal. After that, I anneal when it is reduced by about 50% in cross section or increased by about 30% in length/width, whichever is easier to judge. When rolling square wire, I turn it 1/4 turn on each pass to insure that each corner gets formed by the groove. When rolling sheet, I roll in only one direction, but flip it top and bottom each pass (for no particular reason, it just feels right doing it that way) and anneal before any change in direction. I try to time my direction changes with a corresponding reduction in thickness for annealing whenever possible. I find that it’s most critical with rose gold and white gold alloys that it not get annealed too often, or too hot, or for too long, or cracking and flaking are likely to occur. I also find that with white gold alloys that I only get one shot at it. If it doesn’t turn out right, re-melting for another try is an exercise in pushing a rope uphill.

Your best instructor will be your own experience, so just start melting and rolling. The good news is that even if you mess up, you can always get most of your investment in precious metals back from a refiner. Beats learning to cook with expensive seafood.

Dave Phelps


#3

Hello David,

Thanks so much for your reply! Yes, I agree, practice and experience is best. I melted and poured 8 sterling silver ingots, using oxy/propane little smith torch with whip crucible, and have rolled out 2 of the ingots, but I noticed a few issues along the way, and wished that I had researched pouring ingots here first, and then figured that I had better research forging and rolling a bit more before continuing on.

Any advise is greatly appreciated!

Julie


#4

Julie, are you getting blisters on your sheet when rolling it? My understanding is that is an almost unavoidable problem unless you are a refinery. Anyone have any sage advice on how to cast sterling ingots for flat stock without the annoying blisters caused by oxygen absorption? I have good luck with sterling wire and gold alloys … but can’t seem to get a nice, consistent sheet with sterling. I just work around the bad areas. I tried the “cover it with charcoal” method and made one heck of a mess :slight_smile: I understand the big boys use a inert gas environment.


#5

Tim and I still make most all of our metal stock. When I teach I often start my students with pouring an ingot and making bar, wire and sheet stock. This gets them over the fear of fire and the fear of melting stuff. It was also our first jobs as apprentices.
So here is my procedure on ingot pouring and wire and sheet stock making.
I always lightly oil and then heat my ingot mold before pouring. Some folks like to soot their molds rather than oil. I prefer to oil. Why? For the same reason that when I solder I like to pay attention to the flux. “Huh?” Well when the flux gets clear and glassy looking I know it is very close to the solder temp. That is when I add my solder and concentrate my flame where I want the solder to flow. When I heat my oiled ingot mold, (Think seasoning a cast iron frying pan), as soon as I see the oil smoke I know my mold is getting pretty hot. I then position my metal filled crucible so that while I am heating my metal the flame shoots out the back side of the crucible and continues to heat the mold. I also place something under the mold so that it is tipped slightly towards the side I will be pouring from. When the metal is melted it starts moving like honey. I heat it a little more til is is moving more like water. I then pour in a quick and steady stream into the mold. If you hesitate you end up with voids that will often turn into weak spots and or blisters in the metal after rolling. I always forge my ingots on all sides to prevent cracking at the edges. I do not anneal before this but certainly after. When rolling bar stock to make into wire later I always do a 1/4 turn like David Phelps suggested. Ditto with his advice on plate. I take the rolls down tiny bits at a time and anneal when it gets hard to roll. I never ever cross roll unless I have to and then I always anneal before doing so. Clear as mud? If yall have any questions feel free to contact me.
Have fun and make lots of jewelry.
-Jo Haemer
www.timothywgreen.com.


#6

Hello Jo and Brent,

Jo, Thank you so much for your detailed instructions, I really appreciate it! Ok, I will pour, forge, anneal, roll.

I will need to add tipping the mold to my process and really practice trying to achieve a steady and quick pouring motion…my closed mold has such a tiny openings!

(I used the Rosebud tip on the smith little torch, and tried to get a good flame without too much oxygen…)

(each melt was about 3-4 ounces…too much perhaps?)

Brent and Jo, I did get blisters! Which I only noticed after annealing for the 2nd time…I was wearing my green lens enameling glasses and got the ingot a bit too red…it was after this annealing that I noticed the 1/2" to 3/4" low wide blisters as well as some areas that looked like the surface had begun to melt…sort of tiny melty bumps clustered on surface…

…I was not sure if the blisters were already in the ingot from the (bad) pour, and brought to the surface by the overheating, or caused by the overheating of the ingot…?

I also got some defects that looked like directional (going the long way) stress tears in one or two areas…kind of like what the top of a cake looks like when it cracks during baking…

I shall keep on practicing the forging and rolling, but I fear that my ingots may not have been poured optimally, and may cause defects in the material…I will just have to work around it, and perhaps remelt the remainder with new metal/ casting grain and try again.

Regarding forging hammers, I found this link on an older post, where it shows a large hammer being used to forge bar and rod ingots.

Based on this I am considering ordering from Rio Grande, the Fretz Sledge hammer for forging…and as the article shows, using the slightly rounded side for the sheet ingots and the cross peen for the rod ingots…the Fretz sledge hammer head weighs 20 oz…is this a nice recommended hammer for forging 3 ounce bar and rod ingots?

https://www.riogrande.com/Product/Fretz-SH-1-Jewelers-Sledge-Hammer/112656

I have a similar weight/ face hammer I inherited from my dad, that I polished up…I think I will try that one next.

Thanks so much for the advise!

Julie


#7

Julie,
I am a nut on torch statistics due to my long obsession with torches before I finally made my choice of torch. Your 3-4 ounces for the Little Torch rosebud didn’t seem right, so I checked the manual and it says up to 3 ounces or 85 grams, so evidently someone was using avoirdupois ounces (28 g) instead of troy ounces (31 g). This is for acetylene/oxygen or propane/oxygen. So if you’re using Troy ounces the limit would be 2.75 ounces. Since this is the manufacturer’s claim, I’d say it’s accurate when conditions are just right. If your crucible needs more heat than the typical open casting crucible 2.75 g might be too much, likewise if there is any flaw in your technique. I think I would go with a little less metal, maybe 2-2.25 g. But that’s just a guess.

As to the rest of it, I think Jo Haemer has it covered…isn’t she great?


#8

Julie,
As far as the rosebud tip on the Smith Little Torch, I forgot to add that the recommended pressures are 14 psi for oxygen and 10 psi for fuel and this is the same for either acetylene or propane. For natural gas the pressures would be 7/5 for oxy/fuel. So if your pressures were too low, that would also mean less melt capacity.


#9

Hi RoyJohn,

ok! thank you! I will make revisions to my next melt/pour.

I can adjust the psi on my oxygen, but the propane does not have a two stage regulator…I hope that is ok…

Julie


#10

Hi Julie,
It is hard to know whether you are getting the proper pressure for your rosebud with the regulator you have. There are some regulators that have a dial and a range of 0-10psi, some 0-20psi. If you are getting the flame you like with the small tips and with the rosebud, I would say OK, stay with it. If you can set your oxygen at 14 psi and set your propane where you get a nice neutral or slightly reducing flame, then I guess you are OK and getting max heat out of your rosebud tip. If you are not able to get all the way to a neutral flame with 14 psi oxygen, then you are not getting enough propane for the max heat that the tip can provide.

All that said, it’s nice to have a good regulator with gauges on it. You can use either a propane or an acetylene regulator for your propane with absolutely no safety hazard, they will both work and you will probably find more acetylene regulators than propane for sale. I see some cheap ones for about $30 on line. You might also find name brand used ones in a local pawn shop and I see these in my locale for about $30 each. Just be sure it is not too old, because a rebuild of the diaphragm will cost you more than a new regulator. You could get the used one with a return privilege and take it to a welding supply for them to look at/test with your torch. In my area those guys are very helpful.

You do need to be sure that you are getting the max out of your rosebud if you’re pushing it to over two ounces. Some of those here who are more experienced than I can give you pointers on how fast you should be able to melt and what the metal should look like (rolling, etc.) Hope this helps.


#11

Hi,

RoyJohn, Thanks for taking the time to share your knowledge!

I will experiment with increased psi and observe melt times.

I have another question for the forum regarding forging:

What is the best hammer to forge a bar ingot for sheet?

Based on some research on the forum, for my bar ingots, I used a cross peen hammer, going at a 45 degree angle (basically diagonal), then flipped and repeated on other side…then flipped back and forged going at a 45 degree angle in the opposite direction.

But now after also seeing a rounded flat sledge hammer being used, I am wondering if I should be using a rounded flat face hammer instead of a cross peen…? I felt like the cross peen was very agressive in terms of texturing the ingot…

I figured I would ask before continuing on in my forging.

Any advice would be appreciated.

Julie


#12

Julie- I use a sledge hammer that has had the face polished.
Jo Haemer
www.timothywgreen.com


#13

Hi Jo,
Thanks for your advice. Yes, when I saw the rounded flat faced sledge hammer being used on a bar ingot, it just seemed to make more sense than the cross peen hammer…

Great! a new tool too hunt for! exciting!’

Julie


#14

Hi,

I forgot to give the hat tip for the link I posted earlier, regarding a sledge hammer.

This video is from the Ganoksin Learning Center, and is an article by Ronda Coryell, and covers the steps from making bar and rod ingot molds out of charcoal blocks, mixing and melting alloy, forging, etc in the process of alloying gold for granulation. Very informative article!

Best regards,
Julie


#15

I use a plain, ordinary, cheap, hardware store sledge hammer with the face it came with–very not polished…:-)… The first pass in the mill makes it smooth and shiny (sheen-y), so you needn’t spend a lot of money on a quality forming hammer just for this. I just weighed it—it weighs 2 lbs. 10 oz.

For small melts, you can’t beat charcoal blocks! Iron molds require a lot of heating. I have recently been melting 14K scrap in a groove in a charcoal block without borax, and it comes out fine. I do flame the pieces in alcohol/boric-acid beforehand. The big advantage to the charcoal block is that you don’t have to pour–you can melt the scrap right in the groove!

Janet in Jerusalem


#16

Hi Janet,
Good to know!

I just saw a sledge hammer, very similar to the one Ronda Coryell used in her article, at
Home Depot the other day…it caught my eye because it had the cross peen face on one side…I think I “need it”!.

I have general
purpose Home Depot 1lb and 2 lb sledge hammers that I had purchased to use with my Swanstrom disc cutter (until I was advised to instead use a brass head hammer on this tool so as not to damage it!). I will test those out with my forging.

I do like the idea of using a more substantial hammer to do more of the work for me.

Julie


#17

Julie,
I have the Fretz sledge hammer, which is a lovely looking hammer and very nice to hold and if you’re pounding on thinner sheets of metal it’s great. To forge you need some weight or you’ll have to put a lot more of your own muscle behind it with the thicker ingot. I also have the Peddinghaus sledge hammer. The Peddinghaus’ face is about 2 1/2 time bigger than the Fretz.Uploading… Uploading… As a personal rule of thumb I forge ingots down to at least 10 gauge before I start rolling. If you have a kiln, a kiln makes annealing a snap. I use a kiln when I’m depletion guilding my home made reticulation silver ingots.


#18

Forging is not a procedure of brutal force and a heavy sledge hamers.

Forging precious metal is done by the use of a peen hamer.
This is the reason why its called peening.
Leon Surpin (former orchid member) wrote a very nice article about how to
forge gold or silver.

The goal is to break big metal crystal into many small crystals.
This is done by many (hunderds) light strokes together with turning the
workpiece 45° rather then a view blows of a heavy hammer.
It is a time consuming procedure and time is money.
One of the reasons why people don’t like to peen silver or gold.
An other one is that some craftsmen don’t believe in this pocedure and
rather like to roll it down …period.
A third reason is that your arm and hand needs to work hard to controle
every impact again and again and again.
Not for heavy hammer blows but for many small ones.

I’m not familiar with the new procedure of looking-up old articles.

Best regards


#19

@Sonja
Will you please describe how you anneal in the kiln?

Do you bring the kiln up to annealing temperature before starting?

How long do you leave it in the kiln? How long do you wait before you open the kiln to check it?

So you use a barrier flux?


#20

Yes. Bring the kiln up to annealing temp and place your metal into the kiln. I’m including some photos of the set up I use.

With the exception of the reticulation silver I’m not timing anything, but go by colour. Depending on the thickness of the ingot, rod or sheet it varies significantly so colour is your best indicator. I use pumice in a stainless pan to heat. It produces even consistent results. Of course having a kiln with a window helps! Hope this information is helpful.