I don't know if plumbers use soldering tin with an acid core - I doubt it. They normally use acid separately from the tin and a brush to prepare the material for soldering.
You can make a smell test though. If the soldering tin causes slight smoke and smells a bit sweet it contains rosin.
I don't know of any solders that have a built in acid core, I'm not even sure if it's possible because most acid fluxes are pastes. If you cut the solder and look at it's cross section and see a smaller tube in the middle it's should be rosin core.
Acid flux can't be used on electronics generally... it's acidic, if it ever gets damp, or simply over time the acid in the flux (that's left on the surface) will corrode components and traces. The only way to avoid this is to use rosin flux (not as effective but on a clean solder joint it doesn't need to be) or wash the flux residue away after use, which has all it's own problems.
I don't know of any solders that have a built in acid core, I'm not even sure if it's possible because most acid fluxes are pastes. If you cut the solder and look at it's cross section and see a smaller tube in the middle it's should be rosin core.
With rosin core the flux will build up on your PCB and quickly cool to form a hard deposit usually clearish or browny colour (it can then be chipped off).
"Active" flux is used a lot in mass production. Don't know what the pH is, but it attracts moisture and promotes corrosion. The benefit is, that it washes off with water instead of requiring VOCs, or CFCs. Yes, it must be washed and dried thoroughly but it is commonplace.
You can tell if a manufactured product has no flux residue, it probably didn't use the old fashioned rosin.
My experience, for what it's worth: rosin or acid core flux solder was common and abundant (probably still is) in the larger sizes, such as one might use in plumbing. I've not seen acid core solder in the smaller gages though it may be available.
My experience, for what it's worth: rosin or acid core flux solder was common and abundant (probably still is) in the larger sizes, such as one might use in plumbing. I've not seen acid core solder in the smaller gages though it may be available.
The acid core solders I have are 0.062" and 0.038". The latter is a little finer than a very old spool of rosin core solder that I have for TH construction. True, I have not seen acid-core solder in the very fine (0.015") size used for SMD.
The point is, acid core solders do exist, and the distinction between paste and liquid fluxes is irrelevant with respect to whether the flux is acid, rosin, or organic base. BTW, the acid in low-temp fluxes is often zinc chloride or a similar acidic salt in paste.
A simple test for acid or chloride should help distinguish the solders.