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Solder paste problem


#1

Dear All,

I have a problem with solder pastes. I need them occasionally for
tricky jobs, but most of my soldering is done with ordinary sheet, so
a 2g syringe of solder (costing about �15 at present) lasts for
years. Unfortunately it dries out, even when kept well capped and
bagged. I lost an entire 15g of silver solder like this a while ago
and I’ve got 2g of 9K yellow that’s starting to stiffen up. Is there
any way to resoften it - such as dunking the end of the syringe in a
suitable solvent? And how can I stop it stiffening up in the first
place? It seems like I want to keep it for much longer than the
manufacturer’s intended lifetime.

Many thanks,

Clive Washington
Clive@Atlanticajewellery.co.uk


#2

Dear Clive,

The best way to keep your paste solder and stop it from drying out is
to put it in the fridge when it is not in use.

Neil KilBane
Longford
Ireland


#3

Clive, I had the same problem of paste drying and not wanting to
throw it away. I simply used a very small hair dryer,and while
pressing on the syringe as if to apply it,I kept the dryer heating
the syringe until I could feel it “give”. Works perfectly. I have
never had to throw any away. Best wishes,

John Barton


#4

Hi Clive,

I don’t use my paste solder every day and I’ve had my current batch
of syringes for over two years and the 650 silver is just beginning to
harden up. My trick, if there is one and this isn’t just coincidence,
is that I keep the syringes in an old Velveta Tupperware box , you
know the plastic stuff for refrigerator storage. It has a tight
fitting lid which is usually not snapped tight but which I do keep
on at all times. This box is stored on a shelf fairly close, but not
under, a lighting source. When the 650 became too stiff, I held only
the needle part of the syringe under hot water and it softened up
right away.

Nancy


#5

Hi Clive,

 Unfortunately it dries out, even when kept well capped and bagged. 
I lost an entire 15g of silver solder like this a while ago and I've
got 2g of 9K yellow that's starting to stiffen up.  Is there any way
to resoften it  - such as dunking the end of the syringe in a
suitable solvent?  And how can I stop it stiffening up in the first
place? 

I don’t know if this’ll work for you, but here are 2 schemes that
work for me. I’ve never done a chemical analysis on the paste solder
that’s sold in the US, but I suspect the components are granulated
solder, flux (some include fluorides) and a liquid vehicle (probably
a mineral oil of some type or glycerine). The paste solder I use
comes in a syringe, 1 dwt for gold & 1/2 oz for sterling.

The simplest way to soften stiff paste solder is to soak a cloth in
hot water. Wring out most of the water & wrap the part of the syringe
containing the solder in the cloth. The needle can be on or off for
this procedure. If the needle is on, you may see a little bit of
liquid ooze from the needle.

Another way is to warm the syringe under a lamp with about a 60 watt
light bulb. This approach has a down side. If the lamp is placed to
close to the syringe & left too long, it’s possible to melt the
plastic syringe (voice of experience).

If you use paste a lot, building a ‘warmer’ is the best approach.
I’ve built one that uses a 4 inch (100mm) square by 2 inch (50 mm)
deep covered box. In use, the box is stood on 1 of the 2 inch sides.
Two holes are placed toward the top of one of the 2 inch sides. A 5
watt light bulb is located near the bottom of the other side. A wire
bracket maintains the tip end of the syringes above the light bulb.
The syringes are placed in the box diagonally from the holes to the
bracket.

Turning the warmer on about 5 minutes before using the paste seems to
work for me. With the 2 holes, 2 different temperatures of paste can
be kept ready for use. I’ve used this for paste that was about 6
months old with no difficulty.

Good luck,

Dave


#6

clive -

there will be critics to my method of rejuvenating paste solder, a
necessity when one buys old stock from old lapidaries who have gone
on to that ‘great shop’, it gets technical so pay heed:

step one: remove plunger thingy on hypo, grab a small corkscrew (one
that is always handy for me since i teach myself & need false courage
now & then & can be found on some pocket knives - also handy for
those who ask, ‘shall i go ahead & finish cutting this stone,
or just cut my wrists now’), insert into glop in the bottom half of
hypo-whatis, pull out. put all bits of yucky stuff into strong bowl &
mash with blunt end of table knife, mortar, or the back of partner’s
toothbrush until smooth - or reasonably unlumpy. mix in a few drops
of liquid flux & return to tube. re-assemble.

step two: apply corkscrew for intended purpose for awhile. later,
return hypo to drawer & repeat process next year.

good luck -
ive

ps: please note that i drink only one expensive wine, which automatically
limits my yearly consumption to small amounts (rats!) & cannot in any way be
responsible for some of my posts on orchid.


#7

For what it is worth, I had some paste solder which had hardened. I
decided to pulverize a bit of it in my mortor and pestle, after
which I dribbled in some Battern’s self-pickling flux, mixed it well
to reconvert it to a paste and proceeded to solder with it. It
worked just fine. As it tends to reharden, I just do a small bit at
a time—only as much as is needed. It just takes only a minute or
2 to recondition the solder, and it certainly beats tossing it out
and buying a new batch. Cheers from Alma, in gorgeous Oregon.