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Solder hardness, was Pencil torch as temporary


#1

torch?
Sender: owner-orchid@ganoksin.com
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Hi Kathy, Yes, it does matter. After soldering, the solder will flow
again (sorry for the earlier misuse of “melting” when I meant
"flowing") at about 10 F higher than it did originally (not much
wiggle room there). So, if you’ve soldered a joint with easy solder,
then have to go in and put on another finding, you will need to 1 -
protect the seam (with ocher, rouge, or water-based whiteout) to make
it harder for the old solder to flow and 2 - use extra EZ solder.
Otherwise, your old seams will reflow and could cause a real mess.

So the rule of thumb is to always start with the hardest practical
solder for the job, which leaves you room for adding, if necessary,
later on.

Karen Goeller
@Karen_Goeller


#2

torch?
Sender: owner-orchid@ganoksin.com
Precedence: bulk

    Which brings up a question I've had for a while-- I was taught
that easy, medium, hard solders melted at different temperatures.
Are they all the same hardness after they are cooled and solidified
again? Does it matter which one is used for simple finding
soldering jobs? 

Good question. In theory, at least, they should be the same
hardness as silver, since the melting point has been adjusted by
mixing metals with a lower melting point into silver, and these other
metals evaporate, or whatever you want to call it, when heated beyond
their melting point. (One good reason that you need good ventilation
when you solder!). And once the solder has hardened, it does seem
(at least in my scant experience) to have the same melting point as
the silver. – i.e. if the joint didn’t solder, you can’t just remelt
the solder that’s already there.

Anybody else have more authoritative

Margaret


#3

torch?
Sender: owner-orchid@ganoksin.com
Precedence: bulk

  Which brings up a question I've had for a while-- I was taught
that easy, medium, hard solders melted at different temperatures.
Are they all the same hardness after they are cooled and solidified
again? Does it matter which one is used for simple finding
soldering jobs? 

Regarding “hardness”, aren’t all metals annealed (softened) when
heated? And if so, hardness would not be an issue.

I generally use easy for soldering findings; because I don’t want to
overheat the tiny finding.


#4
     And once the solder has hardened, it does seem (at least in my
scant experience) to have the same melting point as the silver. --
i.e. if the joint didn't solder, you can't just remelt the solder
that's already there. 

Well, actually you CAN reflow the solder … Just clean (pickle),
wash, re-flux, and flow it again. You can also reflow a joint that
HAS properly soldered – that would be one way of disassembling a
piece or fixing a mistake. This is also the principle behind tack
soldering a piece (for example, in marriage of metals, you place your
solder snippets and only partially flow them – you can still see
lumps in the solder – until you’ve hammered the pieces to fill in
any gaps…then you go back and do a complete flow).

A good way to think about solder’s interaction with the metal being
joined is probably this…

As the 2 pieces of metal to be joined are heated, the heat “spreads
apart” their molecules, leaving gaps between them. The solder flows
at a lower temperature than the melting point of the pieces to be
joined, and “fills in” those gaps between the molecules in what’s
known as capillary action. Kind of the same way as your normal paper
towel absorbs water, but on a much smaller scale. The solder always
remains solder … it doesn’t melt away, alloy into the other metal,
or evaporate to any great extent. It has just filled in all those
tiny little molecular gaps.

Because it hasn’t alloyed or changed its composition, it retains its
own melting point and flow point. (although to be perfectly correct,
there is some extremely small component of the solder that does
evaporate or become oxidized and washed away, which contributes to
its flow point the second time around being about 10 degrees (F)
higher – a really negligible amount).

Does this help clarify things a bit?

Karen Goeller
@Karen_Goeller