# Oxygen Source for Torch



## chemist (Jun 13, 2010)

Has anyone ever converted a small Bernzomatic MAPP/Oxygen torch to use larger bottles of oxygen?
These small torches are good for hobby work like melting, but they burn through oxygen rapidly and consume the small 1.4 ounce (43 gram) bottles of oxygen in a few minutes. It would be nice to use one with a larger O2 bottle, but the hose fittings don't match up. 
Any ideas?


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## philddreamer (Jun 13, 2010)

I got a good deal @ a pawn shop, act/ oxi set w/ hoses, regulators. Almost new, for $80.00 USD. Since you'll be needing a gauge & regulator for bigger tank, maybe you would be better off investing in the right set-up.
Depending on the task, I'll use propane, mapp or acet/oxi. :lol: 
I've learned, the more right tools, the easier getting the job done.


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## lazersteve (Jun 13, 2010)

Ditch the oxygen bottles and use a mini-furnace set up with straight MAPP as seen in the Mini-Firebrick video on my website.

MAPP by itself is plenty hot enough, the real problem is your melting set up is losing heat faster than it is being added. 

Steve


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## samuel-a (Jun 13, 2010)

steve, can PGM's (Pd,Pt) be also melted in a firebrick with MAPP turch? (indirect flame)


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## lazersteve (Jun 13, 2010)

samuel-a said:


> steve, can PGM's (Pd,Pt) be also melted in a firebrick with MAPP turch? (indirect flame)




I feel like it is possible, but not in the mini's current arrangement. The brick and dish are both too weak to handle those temperatures. 

I've done a little prototyping with other materials, but have only succeeded at sinstering the platinum sponge, falling short of achieving a good melt.

Steve


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## chemist (Jun 13, 2010)

I use Steve's mini-furnace with MAPP gas, but it is slow and I am always in a rush. 
I like the speed with which a MAPP/O2 flame melts metal. Also, a torch is quite good at pushing those tiny little beads of metal down into the body of the melt and stirring the melt (like in Steve's avatar).


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## lazersteve (Jun 13, 2010)

I'm working on a new design for the mini to improve melt times.

Steve


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## Harold_V (Jun 14, 2010)

chemist said:


> I use Steve's mini-furnace with MAPP gas, but it is slow and I am always in a rush.
> I like the speed with which a MAPP/O2 flame melts metal. Also, a torch is quite good at pushing those tiny little beads of metal down into the body of the melt and stirring the melt (like in Steve's avatar).


I used natural gas and oxygen. I could melt five ounces of gold in less than a minute, starting with cold materials. A rosebud is used, with the flame impinging on the gold, not the dish. With such a large heat source, the dish gets hot quickly as well. 

I have always supported torch melting of gold, without the use of anything but a melting dish. If you use a good quality dish and a decent sized torch, you can do the job so fast that there is no other method that can compete, aside from, perhaps, an induction furnace. 

Harold


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## darshevo (Jun 14, 2010)

Harold_V said:


> I used natural gas and oxygen. I could melt five ounces of gold in less than a minute, starting with cold materials. A rosebud is used, with the flame impinging on the gold, not the dish. With such a large heat source, the dish gets hot quickly as well.



I am curious Harold, do you use natural gas rather than acetylene due to cost, or is it a matter of the acetylene altering the material? I have seen large volume scrap guys use propane in place of acetylene when doing a large cutting job, generally with the excuse that its cheaper in the long run.

-Lance


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## Harold_V (Jun 14, 2010)

For me, it was a matter of convenience, although cost was a big factor as well. 

Acetylene isn't the best choice for melting platinum metals due to the excessive carbon molecules in the gas. Natural gas burns clean, virtually impossible to create a smoky atmosphere, very unlike acetylene. However, it should be noted that a controlled atmosphere furnace can carburize, so it's obvious that there can be free carbon. Aside from an induction furnace, the next best choice would be a hydrogen torch for melting the platinum metals. 

Melting with natural gas has limitations. I could melt a little more than an ounce of platinum, and even that wasn't easy. I am not privy to the temperature of the flame, but it must be considerably cooler than oxy/acet, which is reputed to be in excess of 6,000°F. 

For gold, however, which melts at roughly 1,300° lower temperature than platinum, it was a natural. Never had to worry about running out of fuel, and I kept a spare oxygen bottle at the ready. I was never inconvenienced by running out of fuel in my more than 20 years of operation. Significant in that my torch was in use daily. 

I recommend natural gas above all other fuel sources, assuming you have it at your disposal. It's clean, cheap and user friendly. Lighter than air, so it can escape, unlike propane. 

While I don't have numbers, there's no question, propane is far less expensive than acetylene. Stands to reason considering calcium carbide from which acetylene is made, is a man made product. We must make a product to convert to a second product in order to achieve the end goal. It is also a very unstable gas, readily self ignites (violently) when under more than about 15 psi. To avoid that problem, it is dissolved in acetone in cylinders. Note that there's a red line on acetylene gauges.

Harold


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