Hmm. I don’t seem to have any of the problems you mention.
Shannon’s set up look spic and span clean to me–just like my setup–and with no borax stuck to the top. Don’t know why you find it dirty to use. Perhaps you were using an inferior type of charcoal block?
My charcoal ingots last for ages. They do the job so quickly that they aren’t much affected by the melt. Again, perhaps you were not using the harder type, which are much better for both soldering and melting. The older, simple ones do fall apart quickly. I would strongly advise not getting those for anything.
Not clear why one needs “an accurate estimation of the length and width of the cast bar in relation to it’s weight” (or what exactly that is …:-)…). I make the groove the depth and width I want (like a pencil–just right for the rolling mill). I always start rolling into a square rod even for making sheet, as I like to have the ingot compressed in all directions before rolling out flat.
I make the groove with a very wide, flat graver, so I cut nice squared ends. It takes under half a minute and lasts ages. I put the block on a slant and pour into the groove, so it goes right to the bottom end and takes up as much or as little space as it needs. That way it always comes out square (before rolling) instead of puffing up above the top (like on your 12mm ingot) if the inserted bar doesn’t give it enough space to stay flat . Isn’t it a nuisance having to calculate (or guess?) where to place the insert bar? And it’s just extra work rolling it back down to flat. If your gold ingot is 5 grams and the silver one in the topmost photo is 30 g., then your 10 g. markings seem not to be very accurate…:-(…
Your little guy seems to have a lot pitting/bubbling on the top surface and borax stuck to it, often signs of either overheating or a not sufficiently hot mold. I would heat a mold of that size and weight a good several minutes with oxyacetylene to get it up to the proper heat to pour into it–that’s what I hate most about big metal molds for small pours. And since I started using charcoal blocks as ingot molds, the ingots are smooth and even and without encrusted borax–rather like Shannon’s red hot button on his charcoal.
Not sure what “pre-preparation” you find annoying. The thing I love about the charcoal (in addition to the tremendous advantage of the reducing atmosphere!!) is that there is no preparing beyond making the original groove the first time (a few seconds if done on a wheel). Then I use it over and over. Multiple casts of different metals are not a problem because the pour leaves ZERO metal residue behind, so there is no fear of contamination.
It should perhaps be noted that all the above is really in the context of small pours.
I get it Hans, I like your adjustable setup. I’ve played around with some steel ingot molds myself. My usual one is a heavy steel one that needs to be preheated. My big issue was making white gold ingots the were always too big to then roll down to a useable size. The white would inevitably crack and have problems with a lot of reduction, even with many annealings. I like to experiment and those charcoal blocks are so easy anyone can do it. You can custom make the size stock you want including a thin sheet to roll into flat stock. I just like the simplicity of it. The pours come out of the charcoal so clean too, and they are nice and soft from the slow cool down. It finally gave me something to do with that huge wheel burr that’s been laying around since I bought it too😜
Actually Hans I think $72 might be cheap for that. Looks like a bit of machining and drilling going on there. I can see that working well. Could it make a bar 2x4mm or is that width set by that middle square stock?SD
Hi Janet,
now I dont normlly ask a how to question here, its the 1st time! as what I do as you may have read is quite different to everyone else.
However,
Im intrigued with your mould making from compressed charcoal blocks, and as you may guess ive cast iron moulds here. Id like to try your idea but I need to cast ingots 4 by 1.75 by 3/16th in .
In 999 silver. Ive some 12oz avoir to cast. As Well as some 4.4lbs of sterling all to make sheet.
No problem melting as ive a big Kasenit propane furnace that will take salamander graphite crucibles some 12in by 5in.
any experience in using charcoal block moulds for this size ingot?
Ted.
vladimirfrater2h janetb
Hi Janet,
now I dont normlly ask a how to question here, its the 1st time! as what I do as you may have read is quite different to everyone else.
However,
Im intrigued with your mould making from compressed charcoal blocks, and as you may guess ive cast iron moulds here. Id like to try your idea but I need to cast ingots 4 by 1.75 by 3/16th in .
In 999 silver. Ive some 12oz avoir to cast. As Well as some 4.4lbs of sterling all to make sheet.
No problem melting as ive a big Kasenit propane furnace that will take salamander graphite crucibles some 12in by 5in.
any experience in using charcoal block moulds for this size ingot?
Ted.
Hi Ted,
As I said, I’ve only make pencil size and shape apart from the occasional button just like in Shannon’s photo which I actually melt right on the charcoal block (no pour) when I need a small amount of sheet in a hurry. I always thought of the charcoal block just for small melts, but now that I think about it, the ‘heavy heating’ is done in the crucible anyway before the pour. If you get a good quality charcoal block and heat it lightly before pouring (don’t know if that is even necessary?), perhaps it would work just fine. As I mentioned, it takes a long time and a really strong flame to get those big metal molds hot enough to get a smooth, unblistered ingot, and that whole issue disappears when you use the charcoal mold. (I think underheating of heavy metal molds is the major cause of faulty ingots.) I wonder if the amount of heat from a large pour would shock/crack the charcoal (that’s why I would heat it lightly just to be safe). The charcoal is certainly much kinder to the gold/silver.
I also always bind my charcoal blocks with binding wire–probably a holdover from the early days when I used lower quality blocks. But then, I was also using them as crucibles…:-)… Beautiful melts–for small quantities. I anxiously await your results!
Janet in Jerusalem
Ps Shannon–If you’re still there, please tell us what size charcoal molds you have made. Done any big ones?
PPS Well here is an interesting video on charcoal blocks. According to this, I have the “soft natural blocks”–not the “hard compressed blocks”! https://youtu.be/wD6bdKx_-_g
So Ted I would say that you could make any size ingots you want. You just need to carve it into one side if the charcoal blocks. I’ve been using a big wheel burr. My problem was with white gold and it cracking from too much reduction from big ingots. I’m going to make some sheet next. I just got some 2.5 mm square white gold to turn out well. I rolled them down as small as I could with the mill then I pulled them through a square drawplate. I wound up with some nice thin square wire.
Also for anyone wanting to try this. Esslinger had a charcoal block that’s harder than others. You need 2. I made a very simple thicker wire u shape that I can just slip over the two blocks to keep them together. The blocks are not compressed but just sawed out so they have nice flat sides. SD I’m going to try just using dry hardwood and see what that does.
Haha… I didn’t realize that was the top view of the closed mold…:-)… When I need a small amount of sheet fast, I melt a few scraps on a charcoal block and it makes a little button which looks just like the red bit in your photo.… I just hammer a few times and roll out. Makes real clean sheet.
Can you tell if the Esslinger block is like the hard one on the video I posted? The photos I saw of the hard compressed blocks seemed to be made of course grains, so I was afraid they might not cut in clean lines. And the video said the soft ones were good for cutting desired shapes. The Esslinger photo (on their site) was not as clear, so it is hard to see the grain. Is that what you used in your photos? Your cuts were really clean.
Hi Janet,
Ive got out my good charcoal blocks and will make the appropriate recess etc on the mill. ~Then have a go with a small pour before hitting the 12oz 999 avoir.
If it works or otherwise will update you .
This will happen next week as im in the middle of setting up some tooling for the next production run. !. Normally i prerheat my cast iron moulds so that olive oil smokes off it. then pour through a reducing flame.
Then ill cut off the top piece that fits the lead in , then put it through my power mill.
the only time I hand turn the mill is when ive to reduce a square section then wind back, close the rolls and repeat.
Thats a fun product depicting the iron age using a 6in by 1/4in iron nail as the starting point.
Thought youd like that.
Ted.
Here are some pics of an 18 k ingot being poured into charcoal. This heavy charcoal block is a compressed block. Here is a link to a vid. Pouring ingots into charcoal form - YouTube
Looks like the older blocks are regular wood and the new one is compressed, yes? Do you find the texture of the compressed one harder to cut? It looks like it’s more difficult to get a smooth surface on it. Did you find this affects the finish on the ingot a lot? I suppose it doesn’t really matter because you roll it down anyway.
It’s good doing a vertical pour like that because impurities tend to stay on top and you can just cut or file the top off as opposed to having it smeared over the face of the sheet as happens in a horizontal mold.
That one I poured in the size I needed so I didn’t roll it. It was sizing stock. I love how smooth and clean it comes out. That big torch for casting is oxy acetylene. The compressed one is harder to get a smooth finish but like you said it gets milled after that anyway. It does seem just from that little experiment the compressed block might last longer. I’m still going to try hard wood and see what happens
I’ve been told that but never had confirmation from experience. Aren’t you doing the same thing either way. You’re compressing the molecules and realigning crystal structure.
shiftingmetal20h janetb
Aren’t you supposed to forge all castings before rolling?
scavengerqr18h
I’ve been told that but never had confirmation from experience. Aren’t you doing the same thing either way. You’re compressing the molecules and realigning crystal structure.
Rolling compresses just the surfaces. With forging, you can get the compression to go deeper into the ingot. Ideally, it should be be compressed all the way through.
I usually don’t forge yellow gold or palladium white gold before rolling, but I do forge nickel white gold. A master goldsmith I knew would have his workers forge platinum for ages before rolling…
I remember Leonid Surpin discussing this issue. Here are excerpts from two of his posts on the subject. There is more about this on Orchid .
What's the purpose of "forging" with the hammer before rolling?
Right after casting, metal grains much larger than they should be. Forging breaks it down into fragments, which upon annealing re-crystallize into smaller, compact grains. This is one of the principal differences between handmade and cast jewellery. Metal prepared that way is much stronger and retain polish longer, if fabrication proceeds with direction of the grain in mind.
In my DVD “Eternity Ring” this principal observed very stringently. It allows creating of the structure, which look very flimsy, but actually much stronger that it’s casting counterparts.
Forging step can be avoided if one has industrial mills. First pass should be 1/3 of ingot thickness, followed by multiple small passes rotating ingot 45 degrees each pass, until only half of the original thickness remains. After first annealing, rolling should resume in normal fashion. Not as good as hand forging, but acceptable. This is only possible with very large mechanical mill.
To give general answer is enough to say that it depends on type and design of jewellery. If it is a thick square with the hole drilled in a corner to wear it as a pendent, than absolutely anything will be satisfactory. But if it is a ring to be worn every day and the ring incorporates delicate structures; a goldsmith simply must give it the best chance of survival from daily abuse, by taking every opportunity to strengthen it. Pre-forging is a very important tool in goldsmith repertoire. Non pre-forged alloys are defective from the point of view that they are not as good as they can be. Wether or not it will show as a defect in finished product would depends on the product and its application.
