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Soldering with oxy/acetylene

Hi all! I’ve been in the trade for 47+ years. I’ve used a Smith’s Little Torch oxy/acetylene for the last 30+ years. I follow several “aspiring” groups on Facebook and whenever the subject of torches comes up we get “oh, acetylene is so dirty”! “It leaves my metal dirty”! The one that I really have an issue with is “you can’t solder platinum with oxy/acetylene”! I beg to differ. I’m not a “fine jewelry fabricator” although I have done some. I fabricated one of my buckles in platinum - almost 4ozs., as well as other pcs. Overall I’m very happy with with oxy/acetylene. I know other jewelers that are not only happy with how it performs daily as well as for platinum. It takes a little thought to realize that “cracking” the oxy when lighting eliminates the black “floaties” as does turning the gas off first.
I’m wondering how many jewelers out there are happy with oxy/acetylene and how many use it for fabricating platinum?

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I have no experience with platinum and have only used o/a torches a couple times, but the more experienced artist who taught me to use those torches told me if things were getting dirty or sooty like that, it was because I didn’t have the gas adjusted right. As someone who has largely learned in isolation without interactive instruction, I always wonder if things like this are a result of someone not knowing what they don’t know. Like you might know all the basics of something but miss a detail or nuance, and just not know it can be any different. Good to know that these torches can work for the full range of precious metals, though! I’ve got no plans to try platinum, but who knows, down the road I might have reason to. And knowing I don’t have to invest in a whole different fuel system makes that idea more accessible to me.

It’s been a while since I posted here (but I watch every day). As a platinum fabricator with 60 years of experience…(now I feel really old), here is my opinion.
I used oxy/act. fo a while on platinum, though my training had me use hydrogen/oxy. I had run out of Hydro. and proceeded to use acet.----it seemed to work fine, however i soon found the act. welded pieces were showing stress cracks , not always, but enough I had to figure what was the cause. I switched to Mapp gas/oxy and the problem has never occurred again. There are several variations on Mapp as your welding supply will share. I have a fabrication shop, I do Mig-Tig-fusion and gas welding with oxy/acet. mapp/oxy as well as a couple exotic gasses. I am primarily a platinum guy so lots of pieces under my belt. I use 5%Ruthenium Plat as my primary material, though cobalt and 10% iridium plat. are used on occasion too. I am one of many opinions out there but I highly recommend you contact DHF, Hoover and Strong and Jurgen Metz as fall back on gas/plat compatibility. By the way I use a Smith’s little torch daily, but have several others at hand as the scale increases.
Just my 2 cents worth…

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I think the issue here is what kind of flame you use with silver, gold and platinum and how much heat you need. Silver especially and also gold require a reducing flame with an excess of fuel. Using a hissing, oxidizing flame only leads to more firescale. With platinum, you will need more heat, but no dirt (carbon) in the flame. You can do this with oxy/acetylene and the greater heat available is helpful, but woe is you if you hit the pt with a reducing flame…you’ll get carbon in the metal, stress cracking, etc. This is why many people opt for a water torch, which will not produce a reducing flame. Propane/oxygen can be used, but it has less heat, so it isn’t as convenient for fusing pt or soldering big pieces…I suppose that is why Jim Grahl used mapp gas with oxygen instead…mapp produces more heat., but is less likely to produce a dirty flame. So the issue is that you can use oxy/acetylene with pt, but you better be careful or you’ll ruin some expensive metal.

There are exceptions to every rule…I saw a very nice platinum piece at my friend John Burleyson’s facebook page a while ago and I thought it had been fabricated. He told me it was a casting he’d done and I asked him about his vertical centrifugal caster, but he said he’d used a standard horizontal certrifuge. Something about winding it tighter and just casting one piece at a time…so there’s an exception to every rule. When I visit John later this year, I’ll be sure to ask him about the particulars of his method. That doesn’t mean I’ll try it myself, tho’. -royjohn

I use an acetylene torch but have never done platinum. I wouldn’t switch to anything else. I love it for fusing silver. I may reconsider if I do smaller, finer pieces. I have been told not to use it for platinum and always wondered why. Thanks for asking! It’s nice to learn a bit more.

Hello Phil,
Here’s my perspective as a jewelry metallurgist who retired from Stuller.
There are two important factors to be considered when one is discussing “fabrication” of platinum.
Melting of platinum during fabrication or melting of platinum solders (without actually melting platinum itself) used during fabrication.
Lets consider the first factor - melting of platinum.
Melting could occur unintentionally during soldering or intentionally during casting en route to fabrication.
Even small amounts of carbon when dissolved in liquid platinum causes platinum to become brittle upon solidification. This is the reason experts caution using any gas that produces “dirty” or reducing flame. Even an oxidizing flame from acetylene torch could potentially introduce carbon into molten platinum causing subsequent cracking after solidification. This is another reason why you to keep work bench absolutely clean during platinum fabrication since the high heat required could cause any contaminants to be easily picked up.
Now let us discuss melting of solders used in platinum fabrication.
The above discussion makes it very clear not to melt platinum during soldering. A majority of solders used to solder platinum contain very little platinum metal - they are mostly silver or gold based alloys sometimes with a little palladium addition. These solders typically melt at temperatures well below the melting point of platinum. When such solders are used, judicious use of oxy-acetylene torch should not cause any issues. Such may be the case in your situation!
However, if fabrication calls for color-match platinum solders,watch out! These color-match solders contain mainly platinum and they flow at fairly high temperatures. Their use could potentially cause local melting of platinum and together with the careless use of oxy-acetylene torch may be disastrous.
In order to avoid any headaches, it has become common to suggest not to use oxy-acetylene torches.
Here’s a good news. If you had to melt platinum and after platinum has solidified (no solders were used!) you suspect carbon pick up because you saw cracking, don’t worry.
Just remelt the platinum with a roaring, oxidizing flame keeping the flame covering the platinum till platinum melt stops fizzing. Absence of fizzing indicates that you have burned off all the carbon dissolved in platinum. You will notice now this platinum rolls like butter and you don’t have to send it to your refiner!

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shanaithal - I understand the potential for contaminating platinum. I was plant manager at a large manufacturing facility purchased by Johnson Matthey during their ill fated venture into jewelry manufacturing. They weren’t very helpful when we started casting and fabricating with platinum. We pretty much figured it out, much through trial and error. I did do some research prior to posing this question. To be honest I didn’t read everything that I found but what I did find showed absolutely no carbon in an oxidizing oxy/acetylene flame. I’m sure that an accidental turning of a valve on your torch could screw up some platinum but when one is paying attention the chances are slim. If I had an opportunity to fabricate platinum again I would do it with my oxy/acetylene in a heartbeat.
Several people that I worked with at the factory ended up at Stuller!
BTW - Thanks for your input and expertise.

It wasn’t/isn’t a “gas adjustment” problem. Lack of oxygen mixed with acetylene is what allows the “soot” to form.