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Low temprature solders

#1

Hi all,

I am interested in learning more about low temp solders. A friend of
mine has become very interested in metalworking and she is showing
some innate talent at forming. She is making various copper forms
that she is turning into garden ornaments and fountains. She has a
background in making stained glass. So much of what she is making is
assembled with soft solder containing lead.

I work with precious metals and avoid the lead stuff completely.
Even the copper garden art I have made I used lead-free soft solder.
My experience is limited though with these types of solders. I can
tell that compared to the lead-free stuff that I used, she does seem
to get a bit stronger bond with the leaded solder.

I have been reading on the subject in the Brehpol Theory and
Practice of Goldsmithing book. There is a good section in there on
various solders. But I wondered if any of you could tell me more. My
main concern is for her health. How much is exposure is too much?
Does heating these low temp solders with a torch rather than a
soldering iron, possibly taking them beyond there normal melt temp,
expose you to dangerous fumes? Will a copper fountain that is
assembled with small amounts of leaded solder slowly contaminate the
water that runs through it? Any thoughts on the longevity of these
joints when exposed to the elements outside? (She does apply an
acrylic sealer to the pieces which may help protect the joints a
bit)

I have shared a good deal of metalworking with my friend
involving forming and shaping. I have showed her how to create
greater surface area and contact in her joints to improve the
stability of her soft solder joins. I have also showed her how to
hard solder pieces. But she does not currently have a torch that can
supply enough heat to really hard solder these larger pieces. Also
the copper tends to get so annealed during the process of hard
soldering that soft soldering really does show some advantage.

Thanks for any info on this topic you can pass along.

Carrie Nunes
http://www.metalpetalsworkshop.com

#2

I am by no means an expert, but I have used low temp solders for
years (army, cable harness, semiconductor/electronics, plumbing).
From what I understand, lead solders (even with an electric iron) do
put off lead fumes and will contaminate water. I believe that any
amount of lead above local background levels is considered
unacceptable in water sources. It takes very little lead to affect
the health of children, animals and even adults.

Your friend really should switch to plumbers solders which are lead
free. They really are not much harder to use (as you know), usually
just requiring better/more flux. Or lead-free hard solder/brazing.
You should be able to do a search and get plenty of hazardous
material to print out for her to read. You might also
look into whether or not she is (legally) required to label her
garden fountains and things with “may contain lead”, that may help
her to make the switch to lead free. Lots of people will pass on
things with lead warnings.

You can buy small (cheap) plumbing torches at the local hardware
store for very little money. I’d buy one for them myself before I let
a friend use lead solders.

Hugs,
Dawn B.

#3

While I don’t know anything about the strength of lead solders vs
tin solders (i.e. staybrite et. al.) I know a little bit about lead
poisoning. It is NOT absorbed thru the skin, you have to eat it, or
inhale fumes from hot metal. If your friend has ventilation, she
should be all right. Whether it’s a torch or a soldering iron
doesn’t matter. It’s the heat that creates the dangerous fumes.
Lead poisoning is additive, it takes your body 4+ months to get rid
of it (like carbon monoxide). It’s far more dangerous to children
than adults (the developing brain) but still dangerous to adults.
Lead is present in the environment. Doctors refer to a “lead
balance”. You can have a blood and or urine test for Heavy metals
which will let you know if there’s cause for concern.

I have used lead based solders occasionally, but not enough to gauge
their strength. I have have used Stay Brite solder (96% tin 4%
silver) and Tix extensively and feel that Tix is far weaker. I only
use it when the melting point is critical- i.e. repairing a mystery
metal piece. The trick with soft solders is to increase the surface
area of the joint wherever possible, so if it’s a pin finding, I
hard solder it to a disc or a plate and then soft solder it to the
piece.