Conditioning a Graphite Crucible. Urgent!!

What's this? The kitty can't google?

https://qtena.com/words-about-melting-gold-graphite-crucibles-fused-silica-crucibles-p-6787.html

I know it says for refined gold, but offers info on unprocessed ore as well.

Yes thanks, I did try googling but couldn't find a specific reference to 'conditioning'.
I knew we wanted borax during the melt, but I'd heard mention of 'conditioning the crucible'.
Maybe just the dusting of borax does the trick.
maybe I'm chasing a non-existent prob... better to check now than screw up tomorrow.
Ta
Del

Use SOME flux in the crucible and heat until it is melted. Do this until the bottom is completely coated. If you are only using it for one metal then it isn't necessary.

Cheers...
Del

I would like to do some testing for you, if you could send some gold (a kilo should be sufficient), I will report back to you my results.....GoldenEagle

I'll E-mail it to you immediately.

The guy whos forge I'm going to use has gathered further opinion which seems to be, it'll be fine with borax sprinkled on it.
I've heated it in the oven at 250C for an hour or so which I'd read was a good idea... mind it stunk out the kitchen and Mrs Cat gave me hard stare (I'll have recovered in a day or two)

Del

Found you a little how to video....yeah ya probably want to do this out in the garage,,,,with a fan....

part 1 ....

http://www.youtube.com/watch?v=-rMM-9Pm8Kg

part 2 ...

http://www.youtube.com/watch?NR=1&v=KfbISAEzAQQ&feature=endscreen

Great links cheers
Del

I'm pretty sure silver tipped arrows are good for werewolves but what are gold tipped arrows used for?

Drop Bears.
Actually it's for the arrow plate on a longbow, I'll post a pic when it's done if it works.
Here's the mould I've made, it will be tack welded onto a bit of plate and the gold poured in.

Here's a mother of pearl one on a finished bow (left handed).

Del

Perhaps if you were making her something.....?

You better make Mrs. Cat a trinket to make up for the stink (and the stink eye she gave you).

I'm playing with gold recovery and I think you could just heat your crucible with the borax only and that will clean it out. I'm looking at making my own crucible from a block of hardwood. I found that by heating the wood in a closed can and letting the vapors escape I can make really nice active charcoal. What I also noticed was that the larger pieces of wood kept their shape and so I figure I can carve a hardwood bowl, cook it the same way, and viola! crucible.

Sounds good... be sure to post your exploits
Del

I made my wifes wedding ring by putting borax in a soup spoon and melting it with a torch. I then placed the gold pellets onto the spoon and melted that with the torch. For the mould I used the lost wax process in an investment plaster. This process still needs an oven, to burn out the wax and the resultant carbon. A tip if I may; heat your steel mould to dull red otherwise the gold will solidify very quickly on contact and make a wrinkly surface.

I would prefer to use your mould to make a plug from plasticine or silicon or wax and then use that to make a mould from investment as the steel will carburise and distort. This could leave a big gap for the gold to flow into.

Jim

cheers for the tips. I'll get the mould good and hot.
I'm not too worried about a clean impression, it's just to get it about the right size, it may well get cold forged and shaped. Once inlaid, it gets blended to the contour of the bow.
The mould is just to avoid too much waste and filing and to get a ball park shape (well a shield shape really)
Del
(obviously I'll keep any filinges etc)

One of my college friends used to work in a relative's gold shop. They used panty hose in the sink strainers. This allowed them to use running water to wash off chips and filings without losing them.

Well done. To avoid all filing and waste next time try using wax. You can pour a little melted wax into the recess cut for the plate then remove it and add a stem ( riser ). Then use investment plaster and the lost wax process to get an exact fit. The process is thousands of years old so there is a lot of info around on how to do it. To allow for shrinkage you can shape the wax that you poured into the recess a little thicker in the middle and then the gold piece can be beaten to spread it out. You could also undercut the edges of the recess a little after removing the wax and allow extra thickness around the edges of your wax so you could beat the resultant gold into the undercut. Then burnish the top and voila, no filing. Other experts will point out that the riser will need to be cut off and that produces waste. Not so. Using Archimedes principal you can determine the volume of the wax plug before you add the riser and melt the exact amount of gold you need. Finding the weight of gold per volume was hard so I will save you that problem: Gold is measured in ounces TROY. There are 32 grams per ounce Troy. Only 28.2 grams in an ounce Avoirdupois. So an ounce of gold IS heavier than an ounce of lead. But there are only 12 oz Troy to the pound so a pound of gold is lighter than a pound of lead. Maybe I should offer to sell the advocates of the imperial measurement system a pound of gold for what appears to be a 10% BELOW MARKET price and supply them with a pound troy, thereby making a tidy profit. To get the volume I sunk my wife's wax ring in a large syringe half filled with water as a syringe is conveniently graduated in mils.

I am looking forward to hearing about your next exploit. I like your blog too.

Jim

Cheers, thanks for the info.
Our main problem was we didn't know how much gold the guy had, so it was all a bit hit and miss. If I do anything along those lines again, I'm certainly better prepared and I'd try and do it all myself.
It would be fun to have a try with lost wax, I might do a try out with lead or aluminium just for the experience.
Mind that's another thing on my long wish list of gotta trys
Del

Mission accomplished!
Thanks for the help guys, it moulded quite nicely, but we had more gold than we though so we hammered it down to about 3mm thick with a power hammer. I'll have enough to make a slightly larger more impressive arrow plate.
The guy's workshop was amazing, lathe, hydraulic press, power hammer, huge radial arm drill, 3 forges, sand blaster all sorts of marvellous big boys toys.
It was fun for him too as he hadn't melted gold before.
Del

Ahhh...... my pretty kitt,y give me the gold and I shal care for it well............

It all went well, here's the end result.
More pics on my blog.

Del

Very elegant

Nice work, you've got the touch....

...and pretty fast hands....

.

.

.

.

ON YOUR MARK !

Now on to Agincourt to pluck yew!

I used Borax as a cover flux when melting Chrome Copper to prevent gas pickup from the atmosphere. It formed a thin glass like skin that floated on top of the metal. It left a glass film on the crucible. We used induction melting which required using graphite crucibles. For our gas melting units we had used silicon carbide crucibles since they were much stronger and were safer to use especially with the higher temperature alloys. We would "cure" the graphite crucibles by putting them empty in the induction furnace and applying power, about 25% and getting a red ring around the bilge about 3-4". Then we shut it down, let it cool, then reapply power to get about an 8" red ring. Again shut down, cool and reapply power until the entire crucible glowed red. Once cooled it was cured. In large silicon carbide crucibles the initial firing to cure was partly to allow the glazing to melt and fill the pores and also to fuse the bottom to the base block prior to use. The use of borax or boric acid was probably to seal the pores of the graphite crucible and it also aides in cleaning your gold mix.

See the following from Borax as flux:

"There is a difference between borax and boric acid- it is in the chemical reaction produced when heating boric acid and the extra O2 given off that is too lengthy to go into here but is noticeable in the results in flow of flux and oxide build up (or lack of it) particularly if using sterling or other copper containing alloys like low karat golds, etc. Borax is superior to boric acid, though in refining your scrap (mixing at least 50% 24 kt casting grain with scrap gold and whichever metals you require to make x alloy or in raising /lowering karats in golds) adding boric acid to the metals in the glazed ( with borax!) crucible yields a tougher cleaner ingot that will roll out better and resist tearing, splitting, etc. It is historically the most consistent and reliable and readily available flux. Pure borax in cone form is best, though 20 mule team borax, as for laundry will work too. Borax and water help indicate the flow temperature is about to be reached as it clarifies on the heated metals. Or you can also build up layers of borax by warming the metals and applying,cooling then repeating on application of borax,etc. Bottom line, borax is cheap, consistent superior to boric acid and works on all metals that are non-ferrous."

Although your project is finished I thought this might be of interest.

Thanks, good info.
Del