Make your own liquid Solder Flux

[jojokeo]

It is highly recommended to use a non-corrosive solder flux (rosin) to assure proper contacts and provide an even flow of solder to your parts helping greatly to minimize cold solder joints. I grew tired of using the time consuming paste and tooth pick method on all my pots, switches, and other components and thought there's got to be a better way? I also had a can of paste that was getting old(dark) sitting around for years that wasn't like the stuff I use in a tube. I'd stir it and it would just come out in clumps being rather messy and wasteful - kind of like how old honey gets. Here's my simple solution:

I scooped out a small amount from the can and put it into a small plastic cup/cap that I also put a small amount (a table spoon or two?) of denatured alcohol. Then simply stir into a solution. You'll notice that the solution turns amber colored like a tea. Upon continued stirring the remaining petroleum jelly-ish material will not dissolve - and you don't need it to. This only helps keep it a certain consistency while in the can or tube.

After you have the flux-rosin "tea" simply take a syringe and draw the liquid flux into it staying away from the vasoline-like goo part. Bingo, you're done! It only takes a very tiny droplet now that you simply touch to your solder lug or part and works great. This is by far the easiest, fastest, cleanest, and most economical way to flux your parts. Also the least amount of left over flux-goo on your parts with the least amount of flux "smoke" in the process. Mix only what you need that will go into the syringe. You can buy it like this in a syringe for like $25 in places but now you can have it for not even a dollar. You can also make it simply from tree sap, pine cones, or cheap violin rosin. I may post this later if needed or anyone's interested?

[HotBluePlates]

You could use a needle-tip bottle (sold various places for $1-3, depending on plastic or metal tip). These were used for liquid flux way back when I worked at a p.c. board manufacturer.

[PRR]

> a can of paste

This sounds like, could be, the ACID flux used by plumbers.

It eats copper. Not so much it matters on a pipe or tube, but the stuff starts long-term damage on electronics wiring and terminals. Possession of acid flux inside a computer factory was grounds for instant dismissal.

Please be sure this is Rosin flux.

[jojokeo]

Thank you PRR. However as I said in the very first line of this thread "use a non-corrosive solder flux (rosin)". It's NOT acid flux, I've sweated enough copper piping in my days to understand the distinct difference. But I bet there's many that have no idea of the various types out there?! So this is good for others to understand and be clear about it. I've taken a few photos to show the two I've mentioned and have been using. Both were bought at electronics' stores (not plumbing or irrigation supply houses). You can see the black-ish corrosion from the can or something I was speaking of and how it's gotten a bit hard or crusty from being old. It doesn't work as well as the stuff in the tube when using a toothpick.

[jojokeo]

Here's the other electronics store name brand most people are familiar with. Also non-needle point / blunt tip needle syringes which I got at a Fry's Electronics several years ago. In the last photo are some actual tree sap clumps I removed straight from a damaged and dying Eucalyptus tree trunk with a screw driver. They can be fairly brittle but are as pure as you'll find in nature. Using the syringe over the bottle would allow for greater control with less chances of over application especially in very small or tight places. But I have a similar bottle to that which HBP shows which I've used for working with acrylic/plexiglass solvent welds I might employ in the future. The syringe seems to have zero evaporative loss of the solvent to this point and I've actually used it quite a lot with very little actual amount used making a small amount go a very long way.

[drgonzonm]

Kester, the company that made the rosin flux paste, has some other products, that some of us lazy people may consider. 

check out the link:  http://www.kester.com/products/liquid-solder-flux/

The company provides a flux pen.   

Please, note, this posting is not advertising for Kester, but only posted to show what other solutions, to "pin" soldering.  I am sure other companies have similar products. 

[jojokeo]

Flux pens aren't as easy, quick, nor do they cover the entire lug and on both sides like a simple little drop does. Getting into a 9-pin or 9-lug TPDT switch cannot be done nearly as well or completely with a pen. What I've been implying is that this IS the best solution for "us lazy people".

[sluckey]

Flux pens are nice for pcb work but is just the wrong tool for tube sockets and switches. Liquid flux and paste flux work much better for tube amps. Liquid flux is also very cheap and very available.

BTW, back in the '60s, most all radio/tv shops had a shoebox full of hard rosin chunks. We didn't use it for soldering though. The 'rocks' were used on dial cords to keep them from slipping.

[Ed_Chambley]

Flux pens are nice for pcb work but is just the wrong tool for tube sockets and switches. Liquid flux and paste flux work much better for tube amps. Liquid flux is also very cheap and very available.

BTW, back in the '60s, most all radio/tv shops had a shoebox full of hard rosin chunks. We didn't use it for soldering though. The 'rocks' were used on dial cords to keep them from slipping.

You would rub the flux chunks on the cord?  Like a fan belt?  Never tried that, but it seems like it would work well.  Great radio tip, thanks.

[jojokeo]

I think that rosin is the same as used for violin & chello bowes too-

[sluckey]

You would rub the flux chunks on the cord?  Like a fan belt?  Never tried that, but it seems like it would work well.  Great radio tip, thanks.

Exactly.  If you have a dial indicator that slips or even if the main tuning pulley that slips or just acts jerky, just dress the string with a rosin chunk. One golf ball size rock will last a lifetime. There's probably a good supply on most any pine tree that's too close to the parking lot. Look for the rock hard stuff, not the tacky stuff.

I think that rosin is the same as used for violin & chello bowes too-

Probably where the idea came from.

[pickdropper]

If you want liquid flux in an applicator that's a bit more precise than a flux pen, you can get Metron Markers loaded with flux from All-Spec:

http://www.all-spec.com/products/670-391.html

They come in handy and you can dispense flux quite accurately with it thanks to the needle tip.

[PRR]

Thanks for the clarification. As you note, some people might confuse "can flux" with plumbers' stuff. The "Kester ROSIN" is clearly the right stuff. However it looks like it has gone bad?? Kester usually homogenized it good, no lumps or dark-spots.

As noted, your local cellist has a lump of rosin for making the bow squeak the string. I do not recall it for dial-cords but remember it for similar chores. Gymnasts and some weight-lifters use powdered rosin to improve grip.

> tree sap clumps I removed straight from a damaged and dying Eucalyptus tree

AFAIK, the rosin we want is from Pine trees. True, maybe I am mis-led, living in the Pine Tree State. Wikipedia says "pines and some other plants, mostly conifers". And we get it from Indonesia, among other places (apparently not Maine). Rosin is a mix of many-many different chemicals.

Eucalyptus sap seems to be "kino", chief constituent kinotannic acid. Eucalyptus is a myrtle (genus Rhodomyrtus), not a conifer. It appears to be a very different stuff.

Do you have true Pine trees? Ah, apparently not in the wild. I'm sure you have imported pines, but unless they have escaped and run wild somewhere, their owners may not appreciate you slashing their pines and waiting to collect the sap for distillation. I can just pick sap-balls off my pines (like where the snow-plow hits). Much of the reason the English invaded North America was for pine products: turpentine, rosin, and long light timber for ship masts. My tip of land was timbered-out a century ago for sailing ships. That racket faded and the pines grew back (dang few over 80 years old).

[drgonzonm]

I think that rosin is the same as used for violin & chello bowes too-

The bass players used a different rosin, from what I remember, it was softer than that used by the v,v,&c ists. 

[drgonzonm]

The paper industry used to produce a lot of rosin,  Florida phosphate industry used a lot of fatty acids in their processes, rosin acids were considered a contaminant, incorrect number of carbons in the chains.  If my memory is correct (This was 25 years ago), the contained rosins also converted to fatty acids.  Considering that the rosin acids are reducing acids, they prevent the underlaying copper from oxidizing, Most alcohols will also serve as a flux, as they will also keep copper from oxidizing.  (In one of the labs in a ceramics/material science class, we converted copper oxide from Cu-Be alloys back to elemental copper, by dipping hot copper (above 300 C) into alcohol.  Downside, is the flashpoint, and ignition point of the alcohol. (it would start on fire).
0o
I wonder if glycerine will also serve as a flux?, (Double alcohol?)  Easy test, heat up a copper wire, until the end turns black (CuOx), and dip into the glycerine.  If the tip turns back to copper color, it should work as a flux.

And thanks for expressing your opinions on using flux pens. 

[jojokeo]

Eucalyptus sap seems to be "kino", chief constituent kinotannic acid. Eucalyptus is a myrtle (genus Rhodomyrtus), not a conifer. It appears to be a very different stuff.

Do you have true Pine trees? Ah, apparently not in the wild. I'm sure you have imported pines,

Thanks for the heads-up PRR. Euc sap may have been a mistake. I did read about the pine cones & sap able to be used. So today I gathered up a nice little container amount of stuff from hardened to slightly soft I should be fine to use collected from some local Italian Stone Pines aka Pinus pinea.
 
drgonzo - I read where a small amount of glycerine could be mixed into the disolved liquid pine sap/alchohol mixture I think to help as a wetting agent similar to a surfactant? Does that seem correct to you?

[drgonzonm]

Eucalyptus sap seems to be "kino", chief constituent kinotannic acid. Eucalyptus is a myrtle (genus Rhodomyrtus), not a conifer. It appears to be a very different stuff.

Do you have true Pine trees? Ah, apparently not in the wild. I'm sure you have imported pines,

Thanks for the heads-up PRR. Euc sap may have been a mistake. I did read about the pine cones & sap able to be used. So today I gathered up a nice little container amount of stuff from hardened to slightly soft I should be fine to use collected from some local Italian Stone Pines aka Pinus pinea.
 
drgonzo - I read where a small amount of glycerine could be mixed into the disolved liquid pine sap/alchohol mixture I think to help as a wetting agent similar to a surfactant? Does that seem correct to you?

That was not my thought, but if works,   If my faulty memory serves me, a glycerine has a double -OH (alcohol) group.   Since the alcohols reduce copper oxide back to elemental copper, the chemistry would be one preventing the oxidization of the copper and the metals in the solder.  Back to using glycerine, everything that you described would keep the copper from oxidizing, in addition the glycerine would have less of a tendency to vaporize, so your rosin mixture would remain liquidius longer.