Martin Eastburn wrote:
Sounds like a recycle pit is the best bet.
Martin

Nope. This thing will get patched up.

On 8/7/2015 12:59 PM, Cydrome Leader wrote:
Ed Huntress wrote:
On Thu, 6 Aug 2015 18:07:14 -0700 (PDT), "
wrote:

On Thursday, August 6, 2015 at 3:18:09 PM UTC-4, Cydrome Leader wrote:

Obviously both can and do work. Any ideas on why one might use a silver
solder vs the 50/50 stuff? Harris makes something called Stay-Brite solder
which appears to be something close to or the same as silver solder or
potable water stuff. Is it the same, or can plain lead free plumbing
solder be used on stainless?

Take all my comments wit a grain of salt. I have no experience using 50-50 solder on stainless.

I suspoct 50-50 solder would oxidize with time and not be a good color match.

Real hard silver solder will be harder and a better color match, but a lot more expensive.

I think if I were going to try the repair, I would get some stainless steel and beat it into a shape that would fill in the cut. And then solder that in place, And sand as necessary to blend everything together.

I would use real silver solder , but then I already have some on hand. Second choice would be the stay brite. Notice the name implies that it stays shiny.

I would probably slather on flux and use a propane torch because I do not think I have a soldering iron that is big enough.

Dan

Actually I would make a piece to fill in the cut and then use my arc welder with stainless rod to put everything together. But I have assumed you do not have a welder handy.

I haven't had great luck soldering stainless, although I haven't tried
for 20 years. I once had some great flux that one of our advertisers
gave me as a sample, and I could do it with that. I have two soldering
irons over 300 W and the stainless was thin -- probably 0.020". That
was lead/tin solder, which I still have and use. Stainless has lower
thermal conductivity than carbon steel and it's actually a lot easier
to heat to soldering temperature as a result.

So I don't have nuch help to offer on that score. However, I have a
caution: The OP said this is a darkroom sink. If he's processing film
the traditional way, he'll be using hypo (fixer), and that attacks
silver metal as well as silver halide.

How long it may take, I don't know, but hypo is ammonium thiosulfate.
You probably could look up its rate of activity with silver.

'Just a caution.

Never thought about the fixer eating silver from silver bearing solder.
The guy that made the sink has been making these for decades and knows
what he's doing.

It is true the "factory" solder doesn't match the color of the stainless
at all and is dark grey/nearly black. but it has has in fact lasted what I
suspect to be decades already, and I've seen a bunch of the sinks made by
that company.

There is cracking of the solder in other areas that do not actually get
wet, and I was assured that they can be touched up and reflowed if I'm
familiar with soldering.

The maker was sort of vague about the iron he uses other than it's copper
and gas heated. I wasn't able to find out if it's a torch with a copper
head or just a block of copper he heats with a separate torch.

I ordered the harris liquid flux and a roll of 50-50. Will get a fresh
stainless brush and report back in a week or so, or when I can dig up a
200 or maybe 300 watt iron.