best flux to use

1st off, not spilling the fluid will help a bit. Putting the bottle into a support that prevents that is useful and will also save your work surface.

I've used Ruby Flux (liquid) for 20 years for 99% of my work.  They make a paste, but I've not had a need for it.  I decant the liquid into small bottles that I do not spill.

Personally, I like the paste. Put a dab on the rails and heat it up. When it is bubbling, touch with the solder and you're done.

Rosin flux is good. Acid flux will leave you with rusty rails. I bought mine at the big-box store.

MWB , I have always used rosin core solder ,would the paste be compatible with this solder? ,I still have some liquid left but when i need more i would rather have the paste ,it's just a matter of which brand to use at least with the paste i can have it near me & not have to worry about knocking it over.

Gilly ,Thanks for the information ,i will look for it next time i go to Lowes or Home Depot .

Rosin core solder has the flux. I would think it should work fine if you want additional flux on the surface.

Gerald Marafioti posted:

MWB , I have always used rosin core solder ,would the paste be compatible with this solder? ,I still have some liquid left but when i need more i would rather have the paste ,it's just a matter of which brand to use at least with the paste i can have it near me & not have to worry about knocking it over.

99% of the time I'm using rosin core solder and with the Ruby flux w/o any problems.

However, you haven't stated just what you are soldering together.....

I just solder mostly wires to the track ,or sometimes i do minor repairs on my engines ,mostly wire to wire to tap into power lines ,i haven't had any problems soldering i just would rather use paste instead of liquid being that i am a little sloppy with the liquid .

Acid-type fluxes are meant for mechanical connections.  Rosin-type fluxes are meant for electrical connections.  If you are doing any electrical work, make sure the flux is compatible for such.

Actually, acid flux does an especially extra-nice job when soldering electrical connections.  It also does an especially extra-nice job of eating away copper wiring and electronic components over the course of a year or two.   That's why you don't want to use acid flux when soldering electrical stuff.

Paul ,thanks for your response ,it convinces me to stick with rosin-type fluxes ,which i have been using for at least 10 years ,the only change i will make when i need more flux is to go to the paste type .

The only way to use acid flux on electrical stuff is to have a wash right after soldering and clean ALL the flux off the the part.

A little known fact is, in the bad old days of thru-hole components and wave soldering machines, many of them used acid flux for the soldering, they just had a complete wash step right after the solder pass.  I've even gotten a few boards that didn't quite get the 100% wash, and the acid was working it's magic!

Flux capacitors rule 

( they nailed it all except avoiding the fumes...especially in the eye or you'll look like one of these guys for a bit→   😥  😂)

gunrunnerjohn posted:

The only way to use acid flux on electrical stuff is to have a wash right after soldering and clean ALL the flux off the the part.

A little known fact is, in the bad old days of thru-hole components and wave soldering machines, many of them used acid flux for the soldering, they just had a complete wash step right after the solder pass.  I've even gotten a few boards that didn't quite get the 100% wash, and the acid was working it's magic!

Exactly!  And just try and wash that acid flux out of stranded wiring........... 

It's far, far easier just to tell everyone to use rosin-type flux to start with! 

Probably a good point with some wires.  Personally, other than plumbing, I haven't used acid flux for anything.  Works a treat when sweating copper pipe.

I have a old small tin of KESTER paste. It only says "contains Zinc Chloride". Anyone know if that means it's acid flux. I believe that's the same stuff used in dry cell batteries. 

Zinc Chloride is acid flux.

FWIW, I much prefer paste. I've been dipping into a can of "Radio Shack" rosin-core for as long as I can remember, and probably still have enough to last me until I'm long gone. I always found the fluid-type to be harder to "control"...but that's just me.

Mark in Oregon

I like the paste as well, I use this.  I don't need it for routine work, but there are some wire types that just don't seem to take solder well, and they need a little "help".

gunrunnerjohn posted:

I like the paste as well, I use this.  I don't need it for routine work, but there are some wire types that just don't seem to take solder well, and they need a little "help".

I use the exact same thing (albeit Radio Shack flux I purchased long ago).  I don't even mess around waiting to see IF the connection needs a little extra "help".  I simply go ahead and pre-grease 'em every single time.  A tiny little dab'll do ya'.  Hasn't failed me yet!