Brazing with Chemtane

In my research so far it would seem only Alex Wetmore ( @Alex ) has adopted chemtane as a brazing fuel — has anyone else? Specifically curious if anyone has made the switch from Acetylene to Chemtane and your thoughts re: fillet brazing with both fuels.

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I think there are a lot of brand names for boosted LP. Also search for people running oxy/mapp.

If you want to try it you can get a “steak saver” which is a cheap brass fitting that will let you run a propane regulator on a standard hardware store 1lb plumbing disposable bottle. Those are available with MAPP gas at almost every hardware store. That’s how I got started.

Maybe I’m quibbling, but there’s no such thing as MAPP anymore, they stopped making it in 2008. Stuff you can get now, MAP-Pro, costs much more than propane and only burns somewhere arount 100° or 150° F hotter, not a good value. Technique can easily overcome that slight difference in temperature. I think calling modern Map-Pro “MAPP” is a bit of a scam.

There are anecdotal reports of people saying Map-Pro is enough better than propane to justify the cost difference though. I have not compared them myself so I can’t comment. I’ve used a ton of propane though and I know it can overheat your parts just fine! :wink:

Oxy/propane is great for fillet brazing with good tips. I like the ones from Paige Tools in Seattle. Tight focus and they don’t detach or blow out.


Oxy/lpg definitely gets hot enough and is cheap as chips. I easily do bronze fillets with it.


I just re-upped on acetylene and didn’t die in the process so I’ll probably be good for a year or so. Have a lot to learn about alternatives so thanks for the input.

I have used oxy-propane (at a class) with no real issues, it definitely got hot enough. The stuff I was asking about specifically is this:

But admittedly I know very little about the common fuels and have never handled propane directly or even owned a BBQ.

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Sorry, didn’t answer the OP’s question, which was not about MAPP or Map-Pro. Chemtane burns quite a lot hotter than either of those, and might be a real alternative to acetylene, I just don’t know. Ask Alex Wetmore?

I’ve been using acetylene since the '70s. “Because it’s what I’m used to” is a pretty lame reason, I know, but I’ve never had any strong reason to try any alternative for it (other than propane). Hopefully someone who really knows chemtane will chime in.

In the '80s I worked at a place that used propane and acetylene, both, every day. We used O/A for braze-ons and fillet brazing, propane for lug brazing. Now that I have experience with better tips for propane, I wonder if there’s any need for O/A anymore. The one thing propane can’t do is gas-welding, which I almost never do — not once since I got a TIG welder in the '90s. (OK someone will come back with “I gas weld with propane”, but it’s widely reported that it makes brittle welds, so I will almost definitely never try it myself. Especially if making a product for sale to someone else, it’s best to stay within the accepted standards of the welding industry. But I digress!)

I see Chemtane says it burns in O2 at a slightly higher temperature than O/A, which might be useful in some situation (doubtful), but I think it’s mostly considered safer, and maybe cheaper? I don’t go through enough to worry much about the cost, and the safety seems maybe overblown, since I’ve never witnessed a problem with acetylene in the almost 50 years I’ve been using it. Maybe I’m just lucky?

Ooh I just thought of a reason (maybe) for Chemtane over Acetylene, which is the withdrawal rate limit on Acetylene. If you use too big a flame, the acetone in the tank can bubble up and come out through the regulator, messing up your flame and potentially damaging the reg and the hose. The max withdrawal is proportional to the tank size, so with a big enough tank you can run any tip you want, but a lot of small shops only have small bottles and the max tip size can be a real limiting factor. No rosebuds for example. But I use propane any time I want a big heating torch, so no need to put a rosebud on my O/A rig.

The time or two we got acetone coming through the torch, back in my working days, it didn’t actually cause any big problems. But don’t take this as advice to ignore the withdrawal rate, I’ve heard it really can cause big problems. Again we might have just been lucky. We rebuilt our regs (with new diaphragm and whatever else is in a rebuild kit), and replaced hoses now and then, so maybe that’s why the acetone didn’t come back to bite us. That was with bigger bottles though, with 4 to 6 guys using them every day. I forget what size we used but they were a bit tough to muscle around… Small acetylene bottles really struggle to heat, say, a heavy fork crown. (duh, just use propane there)

Curious to hear from any real experts on any of this. Please no “just TIG it!” though. I have a TIG, but I just like brazing.


Sorry I didn’t see your reply before I wrote my “tome”.
Sounds like you’ll be happy enough with O/A, but consider a second heating rig with oxy-propane if you can afford it (2nd torch, hoses and propane reg). It’s got a lot of advantages, not least of which is the ability to get 20 lb propane bottles everywhere. If you can snag a used medical oxygen concentrator, then no O2 reg needed, and free O2 from then on. No more trips to the welding gas supplier. I got my O2 machine with “low miles” for $200 off craigslist. The common 5 liter per minute ones can keep up with a brazing torch just fine, no regulator needed, just adjust the O2 at the torch.

Doug Fattic is the Johnny Appleseed of O2 concentrators for bike frame building, and he’s always been generous with advice to FBs. But they’ve long been used in lampwork, glass-blowing shops. Don’t try to buy one new though, super expensive and I think you need to have a prescription. Luckily, the users of them tend to die, and the survivors just want it out of the house (sorry if that’s a sick joke). Buying a rebuilt one from certain sellers is an option, but I just took a chance on a used one and it’s been excellent.


I got into Chemtane after seeing the differences in my setup and Alistair Spence’s setup for fillet brazing about 15 years ago. I think Mark was the one who back then suggested that I had the wrong gas for the work that I was doing, but a big limitation was that Victor didn’t offer good small J28 propane tips at the time. In those days I was fillet brazing almost all of my bikes and Alistair was building with lugs, but Alistair used Acetylene and I used Propane.

My BBQ-sized container of Chemtane probably has my lifetime’s worth of fuel in it for my usage scenarios, it’s likely that the cylinder will be aged out of spec long before I drain the whole thing.

That’s a good point about MAPP being gone. It was still available when I made the switch, so that is what I used as my test gas since it was a cheap experiement. I didn’t realize that MAP Pro was so much less of a gas.