Hope you're liquid flux isn't acid flux

Yes

Advisable, yes; necessary, maybe, depending on the chemical composition of the flux. Non-corrosive fluxes exist, and you would have to determine if you are using one. This Wikipedia article has a useful table showing chemical codes for flux and properties of the material.

A useful test: Take two short sections of scrap track or rail, perhaps 2" long, join them with a rail joiner, apply flux and solder with your standard technique. Then put it in storage somewhere near the layout. Come Labor Day (or some other milestone months out), take a close look at the joint under strong light. It will show you what would have happened with no cleaning.

Or try the new no-clean soldering paste

Or you might try the new no-clean soldering paste, first made for use to solder SMD components to PC boards. It leaves very little, if any residue.

Not acid flux and it's 60-40

Not acid flux and it's 60-40 rosin-core solder I bought at my LHS. 

Thanks!

Thanks for the recommendations, guys!

"Not acid flux and it's 60-40

 I find rosin core solder works fine without any addition flux, as Yaron said above , make sure the rail is clean, hit it with heat and touch the solder. If you want to wipe it afterwards just a bit of water on a paper towel should do the trick.....DaveB

No clean flux

Have you used this Joe ? It looks like it is very...thick ? I guess I guess I am spoiled by my flux flowing out of my needle oiler for control of placement and amount. Very few reviews on this product also. Maybe a toothpick application to control it ?

Michael

What I use

I purchased this at my local Lowes.  Works very well and it's non-corrosive.

Just a light cleaning is all that's needed.  I still use rosin core electronics solder as I find that the heat transfer is much faster than just the rosin core solder alone.

Yep, used it

Yep, used it. It's like stiff sour cream. Here's some photos from my Run like a Dream: Trackwork book ...

Same stuff, bit cheaper

Same company, same product, a couple bucks cheaper on sale.

Clean up...

A certain amount of flux will be vaporized in the soldering process, so if you just use what is in the core, no cleaning is necesary. Extra flux is helpful if the rail has lost its shine, but it is easy to over do it. Any residual flux of any kind should be cleaned up, and alcohol is a good solvent for rosin based formulas. Flux is either fresh and sticky, and will attract junk, or burned and hard and will resist paint.

pqe

Thanks again, guys!  You've

Thanks again, guys!  You've shared a lot of useful information.

Yep, heard no acid flux on

Yep, heard no acid flux on electronic soldering all my life.  I always wondered what you would use it for; my dad had to solder plumbing pipes on a camping trailer when I was a kid because water froze in the pipes; maybe thats what it is used for?

I've always used Tix liquid flux for model RR soldering - mainly track - it works great and has a handy brush applicator built into the lid.

Cheers, Jim Fitch

Fluxes for electrical applications

Rosin or resin fluxes are the original electrical/electronic flux.  They are mild heat activated acids, and the residue they leave is amber colored (or brown/black if overheated), and highly hydroscopic.  They can be cleaned with isopropyl alcohol and a stiff brush.  No-clean flux is a more modern flux which leaves a non-corrosive residue (typically a with a white powdery surface.)  This residue is difficult to remove, but does not corrode the connection.  It is hydroscopic, and on circuit boards can cause low impedance bridges between adjacent connections!  Water soluble flux is a newer type of flux, which produces a residue which can be removed with plain water.  Isopropyl alcohol is not useful for removing water soluble flux.   Most fluxes sold in hardware stores are intended for plumbing applications and are stronger acid formulations.  They will produce a residue inside the joint which will corrode the joint as current passes through it, and cause it to fail.  This can not be remedied by cleaning the joint.  If you stick to rosin core solder (the most common electrical solder) you should be OK.  If you want to try some of the more exotic techniques, check out the SRA solder website.  They have a wide variety of products and information. http://www.sra-solder.com/I am not affiliated with them in any way, other than an as a customer.