Flux powder and or paste

Education
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Rightly or wrongly, as a very amateur builder with two frames to his name, I have been using flux powder when brazing. I warm the rod with the torch and dip in a tub of flux powder I have. This, to date, has worked for me and I’ve two frames steel that I ride without issue.

When reading or watching YouTube videos, it appears to me the common method is to use a flux paste applied directly to the tubing.

Have I been doing this wrong and should I use paste? Is my current method acceptable. Can I add water to my existing powder to create paste. If I experiment with stainless steel and silver solder is the methodology different.

Thanks in advance, I’ve tried to research this, but can’t find any specifics on this detail.

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That’s what we used when I learned to braze. I don’t think you’re doing it wrong, but it’s a more cumbersome process. Paste flux probably has advantages beyond the amount of time spent applying it versus warming the rod and dipping into powder flux.

I do however believe certain fluxes work better for brazing on stainless steel. When I use stainless braze ons I’m using Harris stay silver white flux with 56% silver filler rod .

This Gas flux type B is for steel and bronze rod and this Gas flux type U appears to be for stainless and silver though I have not personally used it.

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You’re not doing it wrong, if it works; it works. But I’d suggest that if you’re able to do well with the powder then you’d most likely do even better with a paste applied to the work.

Some flux powders can be mixed to a paste, yeah. You’d have to check/ test a small amount.

Stainless is best done with specific stainless fluxes and filler rod (though can actually be done with some bronze rods and ‘regular’ flux paste).

Edit: I use Cycle Design LFB paste/ Sifbronze 101 rod

Or for stainless: Cycle Design Stainless Light Flux paste/ Sif no.39

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thanks for the responses. If I do use paste, how do you mean it makes it easier?

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It’s been a long time since I brazed the way you describe.

But I’d say…pasting an area just slightly wider than your intended fillet size will better protect the tubing from oxide formation and, during brazing, that essentially means better wet-out and easier brazing.

I think it would also allow you to better use the flux as a temperature gauge?

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Having the paste flux on the tube as it heats up, allows you to see when it turns ‘just right’ and then you know the metal is up to temp and you can add filler. I think also, using paste allows you to get flux inside the joint which will help with penetration.

I have tried several different fluxes and I have settled on 2 :
Stainless LIght Cycle Design for silver based fillers
Gasflux blue for brass/bronze and Nickel-silver

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