# Melting furnace DIY with Perlite insulation



## bemate (Oct 12, 2016)

I was looking at a couple of videos about making your own furnace with propane/butane burners and perlite/Sodium Silicate insulation. Is that a viable option for melting gold powders from SMB-drops?

If so, would it be better to go for a horizontal or vertical design? The horizontal would of course have to be substantially bigger to accommodate the crucible, so I'm thinking a vertical one is better and has a higher efficiency.

Has anyone tried making one of these with Perlite?


----------



## g_axelsson (Oct 12, 2016)

How many kilos of gold do you plan to melt?

Göran


----------



## bemate (Oct 12, 2016)

g_axelsson said:


> How many kilos of gold do you plan to melt?
> 
> Göran



As many as I can get my hands on, which is to say likely none. And I was thinking of making it out of a medium sized casserole, with a furnace volume of maybe a liter for a small crucible. It just looked like it could be an alternative and a fun project.

My wife has an oxy/propane torch she uses to make glass beads and jewelry, it should do fine since it melts borosilicate glass. The problem is it's mounted to her workbench, so not an easy task turn use it for melting small buttons...


----------



## Shark (Oct 12, 2016)

Sodium silicate and pearlite will get soft around 2000*F. There are many types of cement that will reach 3000*F and mixed with pearlite will work decent. This would be a good way to go if your just melting one or two pounds (or less) at a time. The pearlite will not withstand flux's or acids very well. You can buy regular large scale refractory with a bit of searching, most run about $1 a pound or more in 55# bulk bags or box's. This also makes high temp cement look more reasonable cost wise. You can buy (very expensive) coating to help the refractory withstand some spillage but I am not sure it would help much if the spills were on a regular basis. If I were building one now, I would use regular ramable 3000*F refractory, such as used in lining a rotary furnace. This type refractory is usually recommended to be used at a minimum of a three inch thickness. If I were building one from high temp cement I would make an outer casting of cement/pearlite mix then add at least a 1/4 inch coating of pure cement inside and out for strength. Given some dimensions of what you plan to use the furnace for can get you better ideas of how to build one as well.


----------



## Shark (Oct 12, 2016)

My small furnace has an inside dimension of 3 1/2 inches high by 3 3/4 inches wide. I have melted several crucibles of copper in it and pour two 12 ounce anodes per crucible. At 24 ounces of copper I am never uncomfortable that there will be any over flow. I am also fairly sure that 2 pounds would be easily within reach for this size furnace.


----------



## g_axelsson (Oct 12, 2016)

A melting dish for less than $10 and a torch is all that you need for melts up to 0.1-0.2 kg of gold.

Göran


----------



## bemate (Oct 13, 2016)

g_axelsson said:


> A melting dish for less than $10 and a torch is all that you need for melts up to 0.1-0.2 kg of gold.
> 
> Göran



That would of course be the easiest way, both in terms of storage of the equipment and cost, however I was under the impression that a standard propane/butane torch didn't get hot enough to melt gold...


----------



## jason_recliner (Oct 13, 2016)

bemate said:


> I was under the impression that a standard propane/butane torch didn't get hot enough to melt gold...


I found the standard pencil tips that come with Bernzomatic propane torch make it a bit tricky. They're a bit too windy* to keep the heat focused on where you want it, and will blow powder everywhere if you let them. A tip presenting a more widely dispersed flame should help mitigate both of these issues.

* I am sure there's a technical term for this, but it eludes me. :?


----------



## SCB (Oct 13, 2016)

bemate said:


> That would of course be the easiest way, both in terms of storage of the equipment and cost, however I was under the impression that a standard propane/butane torch didn't get hot enough to melt gold...



Propane/Butane is not a problem, I can easily melt 50g of gold in a melting dish with propane/butane.
And if I use my largest burner I can probably melt 100g, though I have never tried such a large amount of gold.
If I ever have to melt more than 100g I can build a makeshift furnace of Kaowool for the propane burner, or just toss it in my oil-burner forge.


----------



## bemate (Oct 13, 2016)

That is comforting news, thanks guys!

I was not looking forward to explaining to my wife why I had dismantled her $200 fancy torch to melt $10 of gold... :lol: 

I am still (most likely) months away from getting any dropped powder to be worth melting, with winter coming, I won't be setting up my planned CuCl2-leach anytime soon, so the cold months will probably be spent reading, planning and preparing my little hoard for processing once the warmer weather comes back.

I do have a small amount of powder dropped from a batch of Gold Chloride salts (like in my avatar), that I might practice on, but that's only half a gram in a filter paper, so I might hold off on that. If I resuspend the rest of my HAuCl4-salts and drop, I will have about 5 grams or so, and the relative danger is quite a lot smaller since I don't have to dissolve the gold myself, just the salts. Could be I'll be making that 5g button as a christmas present for myself...


----------



## snoman701 (Oct 19, 2016)

You will be much happier if you order K23 insulating fire brick and make yourself a small furnace. Use any of the burners described in the abundance of homemade forge instructions online. I've played with refractory of all types, and IFB's are considerably easier to work with, and will work better. 

With that said, a furnace isn't of great use. I'd suggest buying your wife an oxygen / propane burner for her beadmaking for Christmas such as the National 3A-A or 3B-B....excellent torch for either glasswork or melting stuff.


----------



## bemate (Oct 24, 2016)

snoman701 said:


> You will be much happier if you order K23 insulating fire brick and make yourself a small furnace. Use any of the burners described in the abundance of homemade forge instructions online. I've played with refractory of all types, and IFB's are considerably easier to work with, and will work better.
> 
> With that said, a furnace isn't of great use. I'd suggest buying your wife an oxygen / propane burner for her beadmaking for Christmas such as the National 3A-A or 3B-B....excellent torch for either glasswork or melting stuff.



I think I'll probably go for fire bricks and separate burners, more flexible if I want to use the setup to incinerate IC's as well. My wife has an oxygen concentrator I can tap into, but I'll tackle that decision when I actually have something to melt. :wink: 

As for my wife, she has a table mounted Cricket oxy/propane torch now, and she's quite happy with it for her bead making.


----------



## upcyclist (Oct 24, 2016)

bemate said:


> As for my wife, she has a table mounted Cricket oxy/propane torch now, and she's quite happy with it for her bead making.


That name makes me want to assume it's a wee torch, like the Smith Little Torch setup--probably doesn't put out a lot of BTUs, even if the pencil flame it puts out is quite hot. 

Although I may get the rosebud/multi-orifice head for the Smith Little Torch, since we have one at the Lapidary Guild I'm in--that'll give me a chance to see how it does with a melting head. They're not cheap, but they sure are portable (like if I keep it outside for storage, but my studio is in my basement).


----------



## snoman701 (Oct 24, 2016)

bemate said:


> snoman701 said:
> 
> 
> > You will be much happier if you order K23 insulating fire brick and make yourself a small furnace. Use any of the burners described in the abundance of homemade forge instructions online. I've played with refractory of all types, and IFB's are considerably easier to work with, and will work better.
> ...


Did she purchase the o2 concentrator? Is she happy with it? I go through a lot of oxygen, and have considered getting one before.


Sent from my iPhone using Tapatalk


----------



## bemate (Oct 25, 2016)

snoman701 said:


> Did she purchase the o2 concentrator? Is she happy with it? I go through a lot of oxygen, and have considered getting one before.
> 
> 
> Sent from my iPhone using Tapatalk



She's quite happy with the concentrator, though the output is fairly low as it's a small torch. She only does small beadwork, primarily to mount in silver jewelry she makes herself. She mostly uses ordinary Murano glass (soda glass), but the torch us able to handle Borosilicate glass in reasonable size beads, maybe a few centimeters in diameter. The problem is getting it off its table mount in order to angle it down at a crucible, but it might be doable.

She purchased the concentrator from a lady in the Netherlands, she refurbished used medical concentrators for use in small torches. This was quite a few years ago, but I can ask my wife for the contact information if you'd like.

Right now it's buried behind a wall of boxes as we're preparing to move her workshop out to the garage next to my workbench, but I'm going down there today to tidy up a bit, will post the make and model as well as output and such later today.


----------

