Soldering weeny things...?

[Faith]

Hello

So last night something odd happened. I was trying to solder a little piece of sterling tube (2.5 x 3.5mm) to a little piece of sheet (maybe a quarter inch square and 0.5mm thick). And the solder wouldn't flow. Now normally I'm fine soldering a bezel to a base plate, but normally, I'd be using medium solder and it'd be bigger. For this one I was using hard solder (why not it was the first join), and it was a smaller piece of sheet than I'd ever used before. First time round I probably didn't use enough flux, but I pickled cleaned and tried again and still no. It got to glowy melty hot both times, but the solder sat there in a stubborn lump. On the third attempt it got so hot it pitted - so i'll be starting again.

All I can think is maybe I heated it too fast? the little pieces seemed to get hot very quickly and I guess had a small surface area to cool down. Is it possible to heat something so fast it 'misses' solder flowing temp?

Either that or its some weirdery about using tube?

I'd be greatful for any ideas

Thanks,

Faith

[MMM Jewellery]

Perhaps your hard solder is oxidised, as you say you dont use it often. Try sanding or pickling the solder to clean it up.

[Goldsmith]

Faith. if you are using strip hard solder it is usually quite a wide strip, I usually pierce down the centre of the strip to give me small pieces of solder, after piercing I file or scrape both sides of the solder strip before cutting off my solder pieces.
after cleaning the solder surfaces, I flux them with borax, gently heat the item then using tweezers I dip the solder pieces in some flux before attaching the solder piece to the hot solder join, as the piece is still warm the solder will stick to the solder join. Then gently bring the whole piece up to solder temperature and it will run.

I know this is a larger piece than yours, but it shows the sequence;



James

[Faith]

Thanks James & MMM (sorry I don't know your name!)

I feel like the solder should have been okay, I use hard a lot for bezel walls and I did a bunch of ring shanks with no trouble only a few days ago. I use snips to feather the end of the strip and then cut pallions off. Admittedly I don't clean it a lot, but equally I never have, and to be sure I'll test some on some scrap.

I still feel like it's something else tho... Could there be anything about the heating or speed of heating? My limited instinct thinks that's what it was, but I don't understand why...

Thanks
Faith

[Aurarius]

I don't think quicker than normal heating would in itself prevent solder from flowing, provided the pieces being soldered remain at the critical heat long enough for the solder to melt and unite them.

It sounds like either your solder was dirty, or the join between the two pieces wasn't inviting enough for the solder to flow down (either because the surfaces weren't clean enough or weren't tight enough) or one of the parts being soldered didn't remain at the critical heat for long enough, or your solder wasn't solder at all, but a stray piece of sterling.

[Dennis]

There you go Faith, let us know what happens when you try to melt some on a piece of scrap. If it won't flow, its a strip of sterling masquerading as solder, like Mark said. Dennis

[enigma]

Could it be to do with the angle you heated at ? particularly if using tube? Did you heat from underneath?

[Faith]

Thanks all,

So taking Marks advice first, it's definitely solder, it has a bit of masking tape on it (at the unused end) labelling it as solder, it lives in the solder drawer and I've used that exact bit a lot recently. It could have been dirty, but after ruining it, I did have one more desperation go, with a new bit of the same solder, a lot of flux and turned my torch way down (it's only a baby butane hand torch) and that time it flowed. It didn't flow well, the piece was all oxidised and dirty by then, but it did flow. I also think the join was okay, the tube was filed flush with mitre jig, then emeried on steel block, as was the sheet. Apart from that it was just sat on it with gravity - as I would for a bezel wall.

Perhaps i was heating it so fast the two parts weren't ever at the same temp at same time?

Finally Sarah, yes I did heat from underneath for all attempts. That's what I'd normally do, I assume the same is true for tube?

Faith

[enigma]

Yes I would heat mostly from underneath although would also run the torch around a couple of times on top when it was close to flowing point.

[Dennis]

The item is so small, faith and you know what to do, so slight changes in technique will not make a difference.

My second bet is that you have either run low on gas, which makes the flame too cool, or the opposite: that you had too fierce a flame , directed on one part and not the other.

But one important piece of the puzzle is still missing: did it melt fine, tried on a piece of scrap? Dennis.