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Flux Removal after Brass Brazing?

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Flux Removal after Brass Brazing?

Old 01-15-22, 07:01 PM
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Tandem Tom
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Flux Removal after Brass Brazing?

Maybe I'm missing something or I need more coffee but I seem to struggle with the above. A hot water soak after silver brazing and I'm good to go. But after brass/bronze not so much. Maybe I need to soak it longer?
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Old 01-15-22, 07:45 PM
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Brass and silver flux dissolve after brazing very differently. That is why we apply brass flux more sparingly and strategically. Most builders have a soak tank that allows for hours of soaking. I discovered recently (maybe after you were here) that boiling water removes brass flux a lot faster than tap hot water. My wife gave me for my shop our old tea heating pot that seems to be able to boil hot water really fast. It has been a great addition. By the way, Gasflux Type B is easier to remove than other brass fluxes.
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Old 01-15-22, 07:48 PM
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Thanks Doug.
BTW, don't forget to send me those dimensions.
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Old 01-15-22, 08:50 PM
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I can't agree more, the hotter the water the faster the brass flux will soak off. I use an emersion hearer, sourced from a farm equipment supplier. I fill my tub or trough w/ hot tap water. Set the hearing element in the drink. Braze away and soak when the water is real hot. Andy
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Old 01-15-22, 09:09 PM
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Originally Posted by Doug Fattic View Post
...boiling water removes brass flux a lot faster than tap hot water.
I do remember seeing an old hand steamer being used with Soap and Water to steam off Flux. It may have actually been Bronze Flux because they were cleaning joints on Bronze Statues they were assembling. When I questioned the crew they replied that any residual flux would migrate and destroy the statues patina over a period of years.

After washing with soap and water they would steam the joints aggressively and then rub in a paste of Baking Sada (bicarbonate of soda) then wash again with clean water.
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Old 01-16-22, 08:39 AM
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Originally Posted by Doug Fattic View Post
By the way, Gasflux Type B is easier to remove than other brass fluxes.
+1 this. I've never needed anything more than hot water and a wire brush to remove the Type B paste flux. Other fluxes tend to leave glassy deposits that need forcible removal.
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Old 01-16-22, 09:33 AM
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I agree, type b is as close to sliver flux as you're going to get as far as removal goes. Our hot water heater is set hot enough that type b comes off fairly easy with hot tap water. I have some powdered borax flux, and it succumbs to boiling water. Prior to that, I would chip it off with the side of a half round file.
Most fluxes are much harder to get off if you get them crispy. Boiling water and a wire brush should work though.

My LWS doesn't carry brass flux, so I have to order it in. I usually get it from framebuilders supply now that Henry James is gone.
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Old 01-17-22, 06:36 AM
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I should mention that Gasflux Type B is available in a powder form. It is very useful when you need to apply flux in the middle of a braze. You heat up your rod hot enough so when you dip it into the powder it will stick - but not so hot the rod will melt. It can also be a bit tricky to melt it off the brass and onto the joint. Again you have to apply enough heat to the flux on the rod to melt it off but not so much as to melt the rod itself. Usually that requires a rotating as well as a back and forth motion.

Many years ago before I heard of the Gasflux company, I used to buy brass flux from my local welding supply store. It came in a powder form in a can that had a separate small hole in the middle of the lid (so it had like 2 lids). This was for sticking your hot brass in as well as just a general holder for shorter stubs. I still have mine I place near me when I am brass brazing in case I need to add a bit more during my braze. I never brass braze without it being close by.
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Old 01-17-22, 04:58 PM
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I didn't know they had type b in powdered form. You have to go direct to get it?
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Old 01-17-22, 08:18 PM
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Andrew at Framebuilder's Supply is trying to get some as we speak (or was a couple of months ago when I placed my back order with them). I have used the powder for a few years. The one jar that I got back when still has some left, but I like to keep ahead of the curve what with the supply challenges we have these days. Andy
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Old 01-17-22, 11:11 PM
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Originally Posted by unterhausen View Post
I didn't know they had type b in powdered form. You have to go direct to get it?
Yes I get it direct from Gasflux. I just ordered some more for one of my European students. I prefer Type G silver flux over type U for my students too. Its active range is up to 1700º instead of U's 1600º. Getting a joint too hot and running out of flux is a common rookie mistake. I also get my 56% silver from them too. Of course I have had an account with them since the late 70's. I don't know how difficult it is to order direct from them.
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Old 01-18-22, 04:00 PM
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You need to order water soluble flux. Gasflux sells a water soluble flux, I use Welco 17 which is what most welding shops can order in. Bad news is they are not doing more than 8 oz sizes from the manufacturer, at least the last time I tried to order it.
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Old 02-10-22, 10:10 AM
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Originally Posted by Doug Fattic View Post
Yes I get it direct from Gasflux. I just ordered some more for one of my European students. I prefer Type G silver flux over type U for my students too. Its active range is up to 1700º instead of U's 1600º. Getting a joint too hot and running out of flux is a common rookie mistake. I also get my 56% silver from them too. Of course I have had an account with them since the late 70's. I don't know how difficult it is to order direct from them.
It seems Gasflux has setup a "retail" website. I have ordered from them with no problems. https://allthingsbrazing.com/
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Old 02-10-22, 05:29 PM
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Originally Posted by Devin Rickey View Post
It seems Gasflux has setup a "retail" website. I have ordered from them with no problems. https://allthingsbrazing.com/
Thanks, TIL there is silver solder with 0% silver
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Old 02-10-22, 06:49 PM
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Originally Posted by unterhausen View Post
Thanks, TIL there is silver solder with 0% silver
If you mean the "Nickel Silver", that's not solder, it is brazing filler, similar to brass (a.k.a. bronze) but slightly higher temperature and quite a bit stronger.

Yes the "silver" in the name is a misnomer, don't know how that got started, but it goes way back.

One common use for it is repairs on gears with broken teeth. Blob on some nickel braze, then shape the new tooth however you like, even hand-filing if you're good with a file. It's often as strong as the original steel tooth.

I made my first lugless frame for myself in '77 using nickel-silver for the fillets. Naive 19 y.o., I just looked at the chart and picked the one with the highest strength. It was a PITA to file the fillets. They are harder than brass, and kinda slippery, so the file wants to skate off. Not recommended! Brass, such as LFB or C-04, is plenty strong enough as we know, unless your fillets are microscopic, so there's no need for a stronger filler there. If you use it for fillet brazing, plan on laying down clean fillets and leaving them in the as-brazed condition.

You can make use of the higher solidus temperature though, for example putting seatstay caps on with nickel, and then brazing the stay to the lug with brass, without re-melting the cap's braze.

Uses the same flux as for brass/LFB.

Mark B
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Old 02-10-22, 08:15 PM
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1000W water heater elements are available on Amazon for cheap. Stick one down into your water tank and it will heat the water up pronto. A thermostat can also be purchases for fairly cheap so you can set the heater and walk away overnight or whatever.
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Old 02-10-22, 09:06 PM
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Originally Posted by Nessism View Post
1000W water heater elements are available on Amazon for cheap. Stick one down into your water tank and it will heat the water up pronto. A thermostat can also be purchases for fairly cheap so you can set the heater and walk away overnight or whatever.
Just keep the water level high enough to cover the heating portion of the element... I have used a few heating elements and found some to be less durable than others. Not being able to see the electric load and the affects to the element and wires I wouldn't leave the heater going too long un attended. Andy
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Old 03-18-22, 05:31 AM
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I had an epiphany the other day... I got #002 out of the jig and was dreading the flux removal when I had an idea. I work for a company that has a fairly large ultrasonic cleaning tank. I figured hot aqueous solution and ultrasonic action might be the ticket. It worked awesome! I had it in for about 10 minutes at ~130 degrees F. Gave it a fresh water rinse, then into the industrial oven at 250 for about 10 minutes to dry it out. A quick wipe with WD40 and that was it. Before and after shown below.

I think there are "services" with machines like this that may not be too expensive. Sometimes it's a real blessing to have a day job. Cuts into the bike building time but there is always the give and take Happy Friday!

BTW, I took the inspiration for this design from Tandem Toms vintage build... Thanks Tom!


Before

After!
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Old 03-18-22, 07:29 AM
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I would not use any oil or the like on a frame that I was going to paint later. Have done that and been reprimanded by a couple painters. I use a phosphate solution (Navel Jelly) to reduce rust during the process. A good painter will use much the same after prepping the bare frame for paint and some primers contain a rust reducing phosphate component.

Nice looking brazing and the ultra sonic dip isa cool idea. Andy
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Old 03-18-22, 03:20 PM
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I use an ultrasonic cleaner that has a heater to remove flux if I'm doing a lot of brazing. I wish I had gotten a bigger one, but it will clean any joint on a frame one at a time. They make ultrasonic cleaners for cleaning rifles that would be more convenient.

Originally Posted by bulgie View Post
If you mean the "Nickel Silver", that's not solder, it is brazing filler, similar to brass (a.k.a. bronze) but slightly higher temperature and quite a bit stronger.
No, I'm familiar with the makeup of nickel silver. The zero percent silver I was talking about is on the gasflux site. They have zero percent on up to the stuff we usually use. https://allthingsbrazing.com/collect...-0-phos-copper

Not sure they call it something that isn't in it, but I suppose it could be important in some cases to avoid any silver for metallurgical reasons. I think I would call it "silver-free" though

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Old 03-18-22, 04:27 PM
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Originally Posted by Andrew R Stewart View Post
I would not use any oil or the like on a frame that I was going to paint later. Have done that and been reprimanded by a couple painters. I use a phosphate solution (Navel Jelly) to reduce rust during the process. A good painter will use much the same after prepping the bare frame for paint and some primers contain a rust reducing phosphate component.

Nice looking brazing and the ultra sonic dip isa cool idea. Andy
Thanks for the tip on the painting, Andy! I hadn't given it much thought yet. I will probably send it through the ultrasonic again before paint and keep it clean after that.
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Old 03-20-22, 11:13 AM
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Originally Posted by bulgie View Post
If you mean the "Nickel Silver", that's not solder, it is brazing filler, similar to brass (a.k.a. bronze) but slightly higher temperature and quite a bit stronger.

Yes the "silver" in the name is a misnomer, don't know how that got started, but it goes way back.

One common use for it is repairs on gears with broken teeth. Blob on some nickel braze, then shape the new tooth however you like, even hand-filing if you're good with a file. It's often as strong as the original steel tooth.

I made my first lugless frame for myself in '77 using nickel-silver for the fillets. Naive 19 y.o., I just looked at the chart and picked the one with the highest strength. It was a PITA to file the fillets. They are harder than brass, and kinda slippery, so the file wants to skate off. Not recommended! Brass, such as LFB or C-04, is plenty strong enough as we know, unless your fillets are microscopic, so there's no need for a stronger filler there. If you use it for fillet brazing, plan on laying down clean fillets and leaving them in the as-brazed condition.

You can make use of the higher solidus temperature though, for example putting seatstay caps on with nickel, and then brazing the stay to the lug with brass, without re-melting the cap's braze.

Uses the same flux as for brass/LFB.

Mark B
Interesting. As A goldsmith and silversmith for more than 35 years, this “two metal” step is puzzling. Jewelers have access to silver solder with three different melting temperature ranges; “hard, medium, and easy”. These temperature variations allow us to do multiple soldering operations without worry about flowing/ melting previous joints. Are these different melting point solders unavailable for framebuilding?
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Old 03-20-22, 05:54 PM
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I don't know why Mark wrote that book of information, the 0% silver solder is right there if you follow the link.

We don't usually use different melting point silver solders. I imagine those are lower strength? There is one fortuitous aspect of 45-56% silver solders and brass brazing filler in that it re-melts at a higher temperature than it melts the first time. So oftentimes you can just rely on that. With brass in particular, you aren't likely to melt a seat stay cap off by brazing the stay to the seat tube. At least I have never done it.

Nickel silver is often called "German silver." Probably should just be called nickel brass.
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