Kester 186 Liquid Soldering Flux, RMA Rosin, 2-ounce Bottle

In active retirement I repair and restore great old ham radio equipment and antique old radios. The old solder is often so oxidized it won't flow and stick well when parts are replaced. In addition to using new rosin solder, a bit of this flux on the joint to be re-worked makes all the old solder receptive to accepting the new solder, to adhering to braided solder (wick) remover, and to make a good, strong, well-flowed joint. It works great for me! It's supposed to be non-corrosive, but just in case, removing any excess is a great idea!

those who know, use it. those who don”t, should. provides an essential tack to whatever you are soldering, for the solder to jump and stick to. use after cleaning with kester brand cleaning flux, helps prevent oxidation while soldering when used correctly.

This is a handy 2 ounce size with a dispenser. I could write pages of material in this review but I will spare you the long story. The product is works as needed and cleans up pretty easily off the joints. If you are looking for a flux to impress your neighbors and friends, this is your product!

A friend told me about liquid flux. I had been using paste. This dropper bottle and the quality of the flux is great. I work with kids soldering kits, and when they really screw up, it is often the case they have too much solder but not in the right place (up the component lead, but not connecting to the PCB pad, for example). Since there is enough solder, but the flux is long gone, a droplet of this great flux makes it do what it should: make the solder "wet" the connection and flow properly. Yay! Negatives: No easy way to leave needle top on it, yet seal it. I pressed a small eraser over it, but it wound up puncturing the eraser and plugging the tube. Tried a rubber band, but it punched through. I take this on the road, so no convenient way to keep the bottle vertical. I would recommend an alternative if there is one - a "dispenser pen" style.

Works well. Regarding a cap for the needle - I also bought https://www.amazon.com/gp/product/B01MDR7KLP (which has "blunt tip needle storage caps", as well as very large needles) and an assortment of different sizes of dispensing needles. The caps in the linked product won't fit a needle as small as the one that comes with the flux, but will fit ones not much larger. I ended up swapping for a slightly larger needle so I could use one of those caps, and it works well. Now, here's hoping the seller sees this and is able to source similar caps to include :)

This flux has been very easy to use, and is easier to clean up with isopropanol than (admittedly few) other fluxes I've used. I think this is a good general purpose flux for most users and applications, and for me worked better than paste flux for removing oxidation and improving solder adhesion to stranded wire and all components and junctions I've encountered with it. Using this, I now see why flux is considered so critical to soldering, as this flux truly makes everything go more smoothly.

This is the best flux I've ever gotten my hands on. Burns quick, less residue to clean off than other brands- when in doubt go Kester!

Rosin pulls solder in, remains clean, does not have any pungent odor, and stores easily. The provided long term storage cap can get gummed up a bit because obviously resin is a bit sticky/tacky when left out in open air, so I just keep mine in a plastic baggie and it works great. The provided needle tip dispenses the rosin with precision, and will tend to get stuck if left in for longer than a day. It can still be unscrewed by hand easily. This is a tremendous amount of rosin, possibly a lifetime supply if you don't solder very often. I would recommend it for someone who solders daily.