I’ve been looking ALL over “YouTube University” to find a video on how to get the right torch flame for melting silver and bronze. I use a Smith Little Torch with the rosebud tip, with an oxygen/acetylene setup. I see a lot of “How To Set Up Your Torch/OxyAcetylene” videos, soldering videos, and how to melt silver and bronze with a Propane setup, but canNOT find what I need for oxy/acetylene and the Smith Torch. Still having problems with torch blowouts, and lately the oxygen feed keeps plugging up at the tip during a cast. I spent way too long trying to melt the bronze the other day because of this and lost a casting from constant blowouts. So, obviously I’m doing something wrong with the tip - a combination of getting it too close to the metal, not “dancing” enough with the tip, and not getting the torch flame correct. I’ve got the Oxygen and Acetylene PSI settings both at around 10 PSI. I realize I’m sounding like a broken record here, but man, I need help. thanks in advance.
I’m skeptical of the Little Torch’s ability to act as a melting torch for casting. If you’ve got oxygen and acetylene bottles and regulators, I’d suggest getting a full-sized torch to go with them, if this is something you plan to do regularly. They’re not that expensive, and would extend the range of things you can do.
That said, it sounds like you’ve got the acetylene cranked up too high - it should be around 5 psi - and the oxygen down too low. With the acetylene at 5, adjust the oxygen until you’ve got a neutral flame: not the tiny bright oxidizing flame, but with a blue tongue coming out a half-inch or so from the orifices.
I no longer use adjustable regulators, but 10 psi sounds high. You should have no trouble with a small amount of silver, but bronze may be a challenge with the little torch. I use a Meco for melting silver…Rob
You can access the Smith Little Torch manual on line and it states that the psi for acetylene rosebud tip is 14 for oxygen and 10 for acetylene. I thought that was too high, to, but that’s what the manual says. Make sure you have the right rosebud for acetylene, evidently it is different from the one for propane and there’s yet another for natural gas. You shouldn’t be closer than the point of the blue flame cone, which is the hottest part of the flame and if you’re getting closer than that, perhaps that’s why you’re getting blowouts. The manual says you can melt up to 3 oz of gold or silver, and bronze shouldn’t be too much different, but I don’t have an exact figure. Maybe the heat capacity of bronze vs silver gives you an idea? Idon’t have any direct experience withthis myself. I used a Smith LT for a while, but now have a Hoke. -royjohn
royjohn…I looked it up too and that’s what it says. I can’t get near those pressures with my O2 concentrator and unregulated propane LT with the casting tip.That would be quite the blaze at 14/10. Sounds like the OP has some dirt, regulator or other equipment issues…Rob
Ok, this info goes back to boatyard days for me. About forty years ago. To set up a torch set for cutting mild steel(I know that’s not bronze) the acetylene was set to 4 pounds psi and the O2 was set at 20. Depending on the thickness of plate we would go as high 7 on the gas and 30 on the 02.
This is Acetylene I am talking about and not propane. Propane can supply a great of about 3560f. Acetylene Burns you 6300f more or less. Sterling melts at 1640f and Bronze at 1790f.
I do some Delft casting and I have no trouble melting Sterling with a Paige Melting tip and a little bump up on the O2 from the concentrator. But I am melting an ounce max. Bigger melts require bigger heat.
If you are using fixed regulators you may need to go to a different system.
Don
You asked for videos showing the Little Torch rosebud tip flame.
Here’s three:
Andrew Berry
Celtic Dreams - Dave Wilson
Rio Grande
Looking back on all of your posts these past months, I think that awerby’s suggestion is something that you should consider. I use an electro-melt set up these days, but back when I did centrifugal casting I used oxygen/propane with a Victor full size welding torch. That set-up worked really well. I had to get a special propane rosebud tip (different from an acetylene rosebud tip), but the regulators and single hole tips were the interchangeable. You do have get welding hose that is rated for propane. Best to check with your local welding supply company to make sure that you have the correct hose.
Or I think you said once that you have an oxygen/acetelyne welding torch. Have you tried that? Lots of people cast with oxygen/acetelyne.
Andrew Berry and Dave Wilson are both melting in an open crucible. That’s a different dynamic from a more closed-in centrifugal casting crucible. It’s going to be easier for the flame to blow back onto the torch tip with a centrifugal casting crucible. Flame blow back onto the torch tip is a common reason for the flame to blow out. This means you have to be extra careful to make sure the flame isn’t blowing back onto your torch tip with centrifugal casting.
Remember that bronze is harder to melt than sterling silver. Silicone bronze for instance has a casting temp at almost 1900 degrees (so it has a higher casting temp. than sterling). Also it’s about 97% copper, which makes it be more challenging to melt.
Hope all that helps!
Jeff
I got one of the cheap electormelts, too. Used, about $150. I have a Hoke torch now and the Hoke instructions say you can use the tip adapter alone for a large flame for casting. The single hole in that thing must be over 1/16" wide and it threw a narrow flame about two feet long the day I tried it out. Might be interesting and exciting to try, but I think I prefer the more sedate electromelt, thanks! -royjohn
aloha from sunny Hawaii… high pressures mean more gas, more gas means more HEAT OUTPUT… BTU’s per second is more important than high temperature. I use a full sized steel cutting torch to melt large batches. It has a high heat output, as well as high temperature with oxyacetylene. I agree with turning up the pressure on a small torch… more gas is higher heat output.
melting bronze is harder than melting precious metals. As our moderator Jeffg mentioned, the melting point is higher. A high heat output torch tip will be necessary. High pressures equals more gas, more gas equals a higher heat output. More gas is burned, more BTU’s per second. Blowouts are common in melting in casting flasks… burned gas is blown back. Keep the flame directed at a low angle on the metal and let the hot burned gases escape. Try not to get the flame into the backwash…
THANK YOU for the videos! They’ve been most helpful. As far as the Little Torch/rosebud goes, I picked that up after taking a class on jewelry casting from a couple of people who’ve been doing this for many years, and who’ve been teaching for about 20 years. The Little Torch was the one they used in class and the one they used for their own work for just small amounts of casting - under 50 grams - which is about all I’m doing in my small operation. I don’t foresee myself trying to do larger casts. Anything larger than that I have someone else do who has a big setup. The biggest cast I’ve done is a little over 40 grams.
Others here have noted that I wasn’t setting the oxygen high enough, so I’ve made a note of that for my next casting here next week. I’ve cleaned out the tip again and tested it today at the higher oxygen setting and it looks good, so we’ll see what happens. Now, video time…. Thanks again!
Right. I was directing it right over the metal instead of at an angle. Note taken… Thank you!
My instructors at the jewelry school I went to over the winter use the Smith Little Torch exclusively, which is why I got one for myself. One of the instructors has been teaching for at least 20 years or so. The class had no problems melting bronze or silver, but then we had one of the professionals looking over our shoulder during the entire process.
As a couple other people mentioned, the Smith manual (which my used torch didn’t have) recommended the acetylene set at 10 psi and the oxygen set at 14 psi. So my oxygen was set too low. I didn’t remember what it was set at in class - I remembered the acetylene setting at 10 and just went for the same psi in the oxygen. My bad.
I may get another torch setup in the future, but for what little metal I’m casting right now the Smith is just fine.
if you are planning to do larger casting, you might consider full sized oxygen/gas torch. I’ve been using a steel cutting tip and welding oxyacetylene set up for melting… I bought a MIG welder and the gas bottles and regulators at an industrial welding store, years ago when I made wind chimes and wind mobiles out of scrap steel…
The heat output is far more than any small torch… operating pressures up to 20psi, high output flow for gas and oxygen, with very high heat output… an ounce of metal melts within seconds. Can’t be used for soldering unless very careful… to much heat output.