# melting and casting silver in a wood forge at home



## jack thomas (Dec 3, 2012)

hello everyone my name is jack im 21 and very new to the metal melting game. so i made a little rectangle shaped forge today out of terracotta bricks piled around with earth. the bricks sat on strong steel mesh, under the mesh i dug a hollow where my air tube is. the tube is connected to a hose and the hose is connected to a speed adjustable leaf blower. the top of the forge is about 35 by 20 cm maybe bigger. okay so i had a little porcelin mortar that i used as a crucible( it broke, no surprizes there), and a coin that was 50% silver 40% copper 5%zinc 5%nickel. i hoped to get my fire hot enough to melt silver but cool enough that it didnt ruin the grating underneath (silver and lots of its alloys melt at about 1000 c and steel at 1500 I think?.) so anyway i had a sliver of my mortar that managed to stay intact and retain enough of a bowl shape so i put the coin in that and got the leaf blower going. the coin was red and soft in a few minutes but never went truly molten and when it cooled it was just shrivelled greeish yellow crumbly gunk. there was green colouration on the coals and bricks. also i didnt use flux because i just wanted to see if i could hit melting point which i believe i could because my coal bed wasnt optimum and i got it quite soft before it turned too dried poo. so is the metal just wrong? do i need a more pure silver? and if so what is an acceptable threshhold or alloy? whats a good cheap flux or is it non essential? how can i make this work as cheaply as possible?
ps can you use plaster of paris to lost wax cast silver? im planning on making an eclectric guitar bridge. if any one can help id really apreciate it thank you , 
jack.


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## Geo (Dec 3, 2012)

try here. http://backyardmetalcasting.com/


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## jack thomas (Dec 3, 2012)

Thanks geo, cool to see peoples projects come together. haha a guy made kitchen cupboard handles from brass casts of his own fingers.

Turns out you can use POP for LW casting. the plaster acts as a binder for a refractory material. Then kiln to remove wax, about 1100 f apparently, some sources said 2000 f but i think thats for the refractory agregate build up method, as oppose to this POP investment method.

I found this helpful,
http://www.blksmth.com/heat_colors.htm


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## MysticColby (Dec 3, 2012)

It would be very hard if not impossible to melt steel using charcoal or wood + air. however, the heat will speed up oxidation (rust) and it might fall apart. Just be on the look out for that happening.

To reach silver melting temperatures, the crucible has to be in direct contact with the coals
A leaf blower might be too strong of an air supply - how low can it go? too much air and it just blows the heat away

it sounds like you were almost there. add some flux, with that much copper you'll have a lot of copper oxide forming (probably the crumbling goo you mentioned). Once the non-oxidized metal melts, it will pool below the slag.
Some temperature data:
800 C / 1470 F Cherry Red.
~879 C / 1615 F Sterling Silver Melts
950 C / 1760 F Orange. Barely visible in bright sunilght. Dark glasses suggested
961 C / 1763 F Pure Silver Melts
1084 C / 1984 F Copper Melts
1100 C / 2012 F Orange Yellow. Light Yellow in the dark. Visible in bright sunlight.
Also, note that your silver is not sterling. I know you can look up on google the estimated temperature your composition will melt at (actually, I think it's above sterling's melting point, but I don't know exactly)

you can use plaster of paris in lost wax castings - I do it all the time. However, you need to put it through a burnout first. I use an old kiln with some holes drilled in the side, one for a propane torch and the others for exhaust. I usually go by this schedule: 300ºF until wax is melted out (about 30 min/inch), 900ºF for about 1 hr/inch (never exceed 1000ºF), check if there are any water vapors (open lid, does steam come out? if so, put it in for longer) - also check for black soot around sprue, if there is then put it back in for longer. cool slowly until outer surface is ~600ºF, remove from kiln, quick visual inspection looking for large cracks that metal would spill out of, immediately pour metal into it if no cracks. I normally cast in aluminum, but silver will work too.
"1 hr/inch" means 1 hour for every inch thickness at it's thinnest cross section
The mold should have at least 1 inch of plaster around whatever you're casting, and it's advisable to also have a wire frame inside the plaster (this helps hold it together, the plaster gets very brittle after it's baked - handle with care)
get the metal ~100º above it's melting point before pouring into a mold, so it doesn't freeze before filling the mold (also why it's important to pour when the mold is HOT)


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## Geo (Dec 3, 2012)

actually, the first true iron was produced by smelting black sands in a Bloomery. a bloomery used charcoal made from baked wood. some bloomery smelting was done by trenching up the side of a steep hill and then laying logs in the trench being sure to leave open spaces for air flow.then black sand would be poured on top of the logs with more logs on top of that. then the trench was covered with dirt with hole at the top and bottom fire was placed at the bottom and the rising heat would pull the flames into the bloomery. in a few days, the workers would dig the trench out and gather the lumps of iron to be worked into "billets". billets could then be worked into tools or weapons. the incomplete combustion of the charcoal worked in their favor by adding carbon to the iron during the melt making the iron harder.

http://en.wikipedia.org/wiki/Bloomery


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## jack thomas (Dec 4, 2012)

Thank you mystic colby its a relief to have a process i can follow. ive done a bit of research online but its so many little snippets all disconnected generally. I really need a good book. I appreciate the direct help, after all theres nothing better for learning than asking a question. And even stupid questions stop you making stupid mistakes. 

concerning air flow im thinking about extending the hose section of my rig and putting a coke bottle in the middle of the line with a rectangle cut from the side. im hoping with another rectangle piece a bit larger i can cover the hole in the bottle to varying degrees and thus controlling the air pressure. definitely not pretty, but hopefully itll work. theres little blow up mattress electric air pumps that i think would be good, but id have to go buy one.
im going to have to start practicing the pop lw cast, ill start small and experiment with pop and wax mixtures. one thing im concerned about is getting slag in the mould. ill try holding it back with a spoon like im making a flat white.

thanks agin to all. ill try and get some photos up, im really terrible with computers.

regards, 
jack thomas


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## jack thomas (Dec 4, 2012)

thanks goe but i think iron smelting is a bit beyond me, plus if i built that in the back yard the people i live with would lose their (Word deleted by moderator). ahhh maybe oneday. i imagine taking something from the earth refining it, crafting it into something beautiful or usefull has got to be so satisfying. its like true self sufficiency.


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## Geo (Dec 4, 2012)

i use an old thrift store hair dryer for air supply to my chip incinerator. it has low,medium and high settings. i just used metal duct tape and tape a 2 inch pipe on the end of it. you can see it in action on my youtube channel. 10464jeff : http://www.youtube.com/user/10464jeff?feature=guide


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## DONNZ (Dec 4, 2012)

Useful info to save:

http://www.engineeringtoolbox.com/melting-temperature-metals-d_860.html

Metals - Melting Temperatures
Melting temperature of some common metals and alloys
Melting points of some metals and alloys are indicated in the table below:


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## MysticColby (Dec 4, 2012)

just had a read on wiki Bloomery, looks like they never attempt to melt iron in it but instead use carbon monoxide from an incomplete charcoal burn to reduce iron oxide in ore to iron.
From what I can find, wood can burn up to about 1000ºC, just barely hot enough to melt pure silver (~130ºC higher than sterling silver)
Charcoal should be able to get hotter than that, as it's had all of it's volatiles and water driven off.


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## kadriver (Nov 3, 2013)

Geo said:


> try here. http://backyardmetalcasting.com/



Geo,

I am interested in doing some experiments with sand casting using fine silver.

This furnace kit available from backyardmetalcasting.com looks like a good place to start.

Do you, or anyone else on the forum, have any experience that can be shared with this furnace.

I am open to all critical input - I learned quite some time ago to consult the forum before pulling the trigger.

Also, any suggested books or for a source for the tools and equipment needed to do sand casting would be appreciated.

kadriver


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## Smack (Nov 3, 2013)

Book store at Back Yard Metal Casting: http://backyardmetalcasting.com/bookstore.html

Tools, safety clothing and more from M. G. Stevens: http://www.mgstevens.com


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## kadriver (Nov 3, 2013)

Thanks Smack.


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## Smack (Nov 4, 2013)

Any time!


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## Smack (Aug 9, 2015)

Guy casts a stool at the beach.
http://www.wimp.com/pewter-stool


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