chewie

considering investing in a gas flux set up, any disadvantages/recommendations?

unterhausen

seems to me that the main downside of a gas fluxer is cost and upkeep. Andy has one, he'll no doubt have something to add. When I'm doing brazeons, I sometimes regret not having one.

Andrew R Stewart 

Yes I have one and have spoke a lot over the years about gas fluxing. First a note about the thread subject. I know of no framebuilders who see it as an either/or choice. I don't know any who don't use paste flux who also have a gas fluxer.

Pros- Maybe a slight better ability to extend your flux life during brazing. Maybe a better ability to burn less of the paste if overheating. Maybe a bit easier clean up beyond the area covered with paste. The flame is a cool color.

Cons- expense. The flux is pretty volatile and nasty stuff to breath when in liquid form. It finds the tiniest cracks in it's container and bleeds out a growing deposit of said cracks. It tends to do the same in your hoses, spark arresters, flash back arresters, and the fluxer tank piping. It can attack some hose materials. The flame has a cool color.

When I was running mine I learned to have a sacrificial 3' of hose after the tank and would replace this every year. I ended up having to steam clean the tank and valving every few years. I ended up getting a second OA tank/torch set up for when I didn't want any gas flux, just turning off the flux tank didn't seem to stop some flux from emitting anyway.

These days I don't bother with the fluxer on either OA set up. If I did more brazing I would hook it up on my secondary OA set. I don't think it solved any problems but might have made some less skilled brazing less bad to do. Andy

JohnDThompson 

We used gasflux along with paste flux at Trek. Gasflux is nice, but it does make for a bright green flame for which you'll likely want to use a darker lens. And the flux builds up in your hoses; we'd soak them in the same tank we used to remove flux from frames to clean them out, but this might be a problem if you don't have a big tank of hot water for soaking.

Andrew R Stewart 

Glass making eye glasses are offered in a style which reduces the sodium flare, the green color in the flame from a gas fluxer. I use Didymium lensed ones myself for all my brazing.

JohnDThompson 

I agree that didynium lenses are nice, especially with silver where they help highlight the very first pale red when the joint is up to temperature. I still found the gasflux flame too bright with didynium, and used No. 3 green lens.

And sodium produces a yellow flame. It's the boron in the boric acid flux that produces the characteristic green flame:

Flame Tests

Andrew R Stewart 

John- Thanks for the correction. I was just rehashing what I read in the past on forums. But my comments about the Didymium glasses helping with gas fluxed flames is from my experience. Andy

chewie

thanks for the advice, it sounds like its messier than i would have expected. i find flux paste fine but am operating within a very limited space so my main hope was that gas fluxing would cut down on some of the mess and speed up the process a bit by cutting out the soaking stage. Sounds like equipment pays a big toll though.

Doug Fattic 

I’ll just add for the record that I did not like using a Gasfluxer. I know some of my colleagues feel differently. The bright flame made it harder for me to see what was happening at the joint. The flux gunked up everything it passed through. I have always found paste flux to be sufficient. Where I could see it shine is when doing constant brazing in a production environment. It is possible that a beginner might find an advantage not burning off all their flux because it takes them much longer to braze a joint. However I also know they would have a harder time with the brighter flame. I’ve got one for sale if anyone is interested after my review of their advantages .