The difference becomes obvious in due time, but not right away.
When joint and solder have the same temperature, which are the
condition in paillon ( no pick ) soldering, the solder penetrates
very deeply into the surface of the joint. It becomes an integral
part of the alloy. If pick is used, due to difference in mass,
solder is much hotter than the joint and it simply adheres to the
surface without penetration.
A couple comments.
First, properly used, the pick is only a means to place the solder
accurately and sometimes to help guild itâs flow. You melt the solder
just enough to pick it up on the pick, but it solidifies there. You
then heat the joint area until you can touch the solder, still solid
on the pick, to the joint, and have it melt down just as it would do
with the paillon. The pick guides placement. Properly used, it
shouldnât be a case of the solder already being much hotter than it
needs to me when introduced. If thatâs happening, youâre doing it
wrong. The pick is not a means of introducing already superheated
liquid solder to a cooler joint. That just doesnât work very well at
all.
Second, if the solder is way too hot, as you imply, and the joint
not hot enough, the solder will not flow properly into the joint
until the temps equalize. If it flows, then the temps are pretty much
where theyâd be if you used paillons. Even if the solder briefly is
hotter than it would be as a paillon, the moment it touches the joint
and melts down into it, itâs temperature will equalize with the much
more massive joint. So the degree of penetration of the solder into
the joint, and from there, diffusion into the parent metal, is about
the same, and still dependent mostly on the torch control and heat
control over the parent parts of the joint. Slight or even
substantial overheating of the very tiny mass of the solder wonât
have much effect on this, IF the solder has been flowed evenly, and
looks right.
If itâs not, and gives the sort of âcold jointâ you imply here, then
it wonât have the same appearance as a properly flowed joint either,
Thatâs true with cold joints achieved by use of pick soldering, or
with placed paillons, and in both cases, would be more the fault of
uneven heating of the two pieces of metal being joined.
The situation you describe of joints not being well adhered can
happen with either paillons or solder pick placement, and would be
due to insufficient heating so the solder does not fully wet and
penetrate into one or both sides of the joint. Factors here are both
the temperature of both sides of the joint being enough to flow the
solder, and also, the amount of time the joint is held at those
temps, allowing additional diffusion of the molten solder into the
parent metal, which increases the joint strength. Iâve seen plenty
of joints that have failed for one reason or other, heads soldered
on, or ring sizing joints for example, where obviously the joint was
done too fast and the soldering not allowed to fully complete.
Thereâs no reason to assume this was because of pick placement of the
solder, however. Iâve seen it with joints I KNOW were placed paillons
(such as on platinum joints, from an era before people tried exotic
metal solder picks with platinum, or those where I happen to know
the goldsmith didnât use picksâŚ)
However, Leonid, there IS sometimes a notable difference in pick
soldered joints and placed paillons. With placed paillons, the solder
melts only once, and generally is not overheated in the process. With
pick soldering, you are correct in stating the potential (though itâs
not inevitable, if the pick is used with skill) for the solder
getting too hot. If, usually during the initial melting and picking
up of the solder, it gets much hotter than itâs melting point, then
some of the more volatile componants of the solder alloy may be
driven off, or oxidized. The result is that the solder may end up
with a somewhat higher melting point, which can affect how much heat
is then required to melt it into the final joint. Normally, this is
not a major effect unless the solder is seriously abused. However,
what can also happen, especially with easier melting grades of
solder, where thereâs often more zinc to burn off, is that the end
solder joint can sometimes end up with a bit more pitting and
porosity if the solder was overheated. This doesnât take time to
become apparent. You see it right away when you clean up the joint
and itâs got a row of pinholes in it. It doesnât so much affect the
long term durability of the joint, just the looks and craftmanship of
the joint. Other causes of the same thing are a poorly fitted joint,
dirt on the metal, solder, or flux, or things like an overly
oxidizing flame, etc. But frying the crap out of the solder alloy
before it ever even gets to the joint is a pretty good way of
getting a less than perfect joint. Thatâs certainly true enough. Iâd
just point out that this is in no way inevitable, if the solder pick
is used with some skill.
No matter how you look at it, soldering is a skill. It takes skill
to do it well by any methods, either with or without a soldering
pick. Used poorly, the pick may indeed make it seem easier to solder,
but the results may not be the equal of what good soldering with
placed paillons will give. But placed paillons also requires skill to
keep things from messing up, and done poorly, the results can be
equally unsatisfactory. Whether or not you use a soldering pick will
depend on many things. The metals and solders youâre using, the type
of jewelry youâre making, your torch and skills with it, and simply
youâre preferences. There is room for both methods, and either one
can be used, when used correctly, to achieve excellent work.
Peter Rowe