Silver Solder Problems

[paul]

Seems like I've totally hijacked this thread! Sorry gwrfan!

I'm using one of these at present...

www.rekri8.co.uk/Go%20System%20DIY/but-propane/butproindex.html


Is this going to get the work hot enough for silver soldering? I bought an additional nozzle-thingy to give a finer jet but it just creates a hugely long wobbly flame rather than a fine tight one as I'd expected...maybe I need to adjust it somehow?

Exactly how hot shoud I need to get say a copper/brass joint? Red hot?


I noticed in other threads mention of firebricks to create a nice warm environment (!) - are they necessary or can something be improvised? At the moment I'm putting the work on a ceramic bathroom tile (!!) to stop heat flowing away.

Whatever happens with the present boiler I know next time I'm going to try proper silver solder and resist the temptation of bodging the solder into the flame to get it to melt (I think fear of desoldering nearby stuff does this to me!).

Thanks for all the help - this is a fun learning curve.

[gwrfan]

Hi Paul,

No worries about hijacking the thread, haha. Actually, that's what this site is about. We all learn something, for better or worse as they say.

As to your question, much will depend on what it is you are trying to solder. For silver soldering (600+ degrees C), you must get the copper up to red heat, usually known as cherry red, or thereabouts.

A great source of information is here:

www.alanstepney.info/page35.html

As you will see, many people use two heat sources, one to heat the 'body' of the boiler, and the other to actually solder what needs to be soldered. Copper will conduct heat as you appreciate, and therefore needs a constant heat supply, and not just in the local area. For small fittings, pipework, etc, your small gas burner will probably suffice, but I think you will use quite a few cartridges, and you'd be better off investing in something like the Sievert equipment, and a small bottle of Propane, say 4.7 kg, which costs me about £11. Even this is not sometimes sufficient to get the job really hot, and therefore another heat source/burner is sometimes required.

Firebricks are very useful, and will save you lots of gas, as they contain the heat, and direct it back onto the work being soldered. I have several old firebricks, and until I ever get around to building a proper hearth, I use a couple of them, one flat, and one as a backplate, to concentrate the heat.


Now, I must drink my cold cup of tea, the other half is complaining, haha.

Geoff

[the_viffer]

paul said:

Seems like I've totally hijacked this thread! Sorry gwrfan!

I'm using one of these at present...

www.rekri8.co.uk/Go%20System%20DIY/but-propane/butproindex.html


Is this going to get the work hot enough for silver soldering? I bought an additional nozzle-thingy to give a finer jet but it just creates a hugely long wobbly flame rather than a fine tight one as I'd expected...maybe I need to adjust it somehow?

Exactly how hot shoud I need to get say a copper/brass joint? Red hot?


I noticed in other threads mention of firebricks to create a nice warm environment (!) - are they necessary or can something be improvised? At the moment I'm putting the work on a ceramic bathroom tile (!!) to stop heat flowing away.

Whatever happens with the present boiler I know next time I'm going to try proper silver solder and resist the temptation of bodging the solder into the flame to get it to melt (I think fear of desoldering nearby stuff does this to me!).

Thanks for all the help - this is a fun learning curve.

I think it depends on what you are soldering. I often use just the same torch for silver soldering fittings and minor components as well as jewellry. You'd not get far silver soldering the foundation ring on 7.25" Duchess with it.

Personally I like a fairly wide flame because I think you should try and get the whole local environment of the job hot not just a tiny area.

The right temperature depends on the solder but it is a good glowing red. You'll know when you are there.
Flux the joint with a paste of flux and water. (Tippex is great btw for stopping the solder running where you don't want just paint round before heating. It needs to be the non-water based version I find).
Hold the solder rod in the flame for a few seconds then dip in the flux to make some flux stick to the rod.
Heat the job. The water evaporates, then the flux goes bubbly then it goes watery. When the job is nice and hot just touch the solder rod on the joint. If it is hot enough then a bit will melt and run all round a small joint ("flash") or into the hot bits of a big one. If it is not hot enough take the rod away and heat the job a bit more. It has to be the heat in the job not the flame that melts the solder. If you are doing a long joint you may need to move slowly round the joint getting it hot enough bit by bit to melt the solder.

As soon as the solder has flashed all round the job stop heating. There is nothing to be gained by further heating of a joint where the solder has run. You'll not improve it and you may boil of some cadmium or zinc.

Thereafter schools of thought vary. Some say quench while hot as the thermal shock dislodges some of the black copper oxide and flux residue. Some say leave to cool.

Some say soak in dilute acid (eg citric acid) which dissolves the copper oxide. Some say soak in alkaline solution which dissolves the flux.

You don't have to use proper fire bricks. You do need to be careful that what you are using doesn't break up under heating (and it doesn't have any soft solder on it). For small jobs I use old radiants from gas fires.

Cheers

[jgb7573]

As an alternative to fire bricks I use ordinary house bricks. So long as they are kept dry they last a good while and are both cheaper than fire brick and easier to find. They work just as well.

Anopther dodge (from a member of the club, not me) - I have a pair of grooves ground in one of my bricks at right angles to each other. I then rest bits of brass etc. in these for soldering. Easy elbows!

[havoc]

A good red in tempered light will do. In bright sunlight you will overheat (guess how I know). The easiest way I found is to flux the piece, and then put a few scraps of solder in the flux when they melt and start to wet the piece you know it is hot enough. Depending on the piece you work on, you can directly put on enough solder or add later.

I use a Sievert Promatic with a 3336 burner. Works fine for gauge1. www.sievert.se/us/promatic.htm A few firebricks are a great help. Any diy will have them for people wanting to build a bbq. I wouldn't trust tiles, if the glazing should chip while you are working it can be dangerous, wear eye protection!

If you braze in steps, apply a layer of flux over the already brazed parts.

[chris vine]

Hi again,

Practice lots on some odd bits of metal.

Use plenty of flux and as Havoc says, put little bits of solder in the joint. This way you will see when you get to temperature as it will nip into the joint.

I would only use a stick of solder and apply it hot when it is a really large job and even then I would prefer to have the solder in place and ready to go....

Have fun
Chris.

[paul]

Thanks everyone for all the tips and ideas, this thread has been very informative and helpful :-)

[the_viffer]

cvine said:

Practice lots on some odd bits of metal.

I would only use a stick of solder and apply it hot when it is a really large job and even then I would prefer to have the solder in place and ready to go....

Have fun
Chris.

I like to use commercial silver solder paste ready compounded with flux for the smaller job. Very neat and very quick.

I find with cut up bits (which I believe the jewellery guys call palliasse although I thought was a French word describing the British on holiday before they acquired a sun tan) the flux bubbles up on heating and displaces the bit of solder leading to bad words and a less than gruntled the_viffer.

If you have not tried silver solder paste I recommend you give it a go.

[havoc]

If you have not tried silver solder paste I recommend you give it a go.

Any references to brands/shops? I would like to try this for small jobs.

[the_viffer]

Hi Havoc

I do some jewellry making and so I use "Easy Silver Solder Paste" ex Cookson Gold (www.cooksongold.net) because the silver content is high enough for the Assay Office to hallmark the finished item.

Chronos (www.chronos.ltd.uk) sell JM Silverflo55 paste which doesn't have a high enough silver content to satisfy the Assay Office. I think it may be more expensive than the Cookson Gold product and have a shorter shelf life.

I've no connection with either company but in my experience they are both among the more reliable.

Good luck

[SteveW]

Guys,

Something I've never seen any comment on is doing the flux+water bit in different hard/soft water areas.

1. Does a drop of calcium in the water cause any problems?

2. Does the liquid solder simply displace it as it heads for the base metal?

3. Would using distilled water solve any thing?

[the_viffer]

Steve Hi

We have fairly hard water and it doesn't seem to cause us any problems with flux. I'd be a bit surprised if the flux were that sensitive to a bit of calcium. The flux's job is to dissolve contaminants and I imagine it'd dissolve any calcium ions too.

Having said that I'm about the last person who'd stop anyone from a bit of experimentation. So give it a go and see if distilled water is better.

BTW a drop of washing up liquid in the flux water is good I find. While it won't soften the water does help the flux paste wet the job

[ridleyian]

Hi Guys
To return to the original subject, does anyone know the brand of suspect solder? I used Cup alloys easy flo 2 clone on my 'Enterprise' boiler and I am looking for an excuse for a couple of stays which refuse to seal!
Cheers
Ian

[malc100]

Hi folks , I read with interest your discussion on silver solders, so some info please I`m an elec tech who does work in supermarkets and as a consequence see a lot of refit work for the frig side of their buisness, the frig plant comes all ready built!! but the pipework is routed and soldered on site and theres bloody miles of it after its been soldered its not pressure tested but is put in a high vacuum to boil out all moisture , then it runs at its normal pressures on a bad day 350lbs( hot day and crap in condensers) . no flux is used, no cleaning of joint, a bushy oxy accetaline flame and the more crud and oil they can get in the area the better, but still get good joints . its a silver solder I`v asked the spec but you don`t see any packets just great wadges of the stuff lying about , when soldered it`s a silver joint with a tinge of copper colour, the temperature they use is high and discoulers (oxidises?) the pipe whats with all this pickling on model boilers before you start, what is this stuff they use is it any good for our boilers? I bet someone out there knows MALC

[the_viffer]

Hello Malc

What you use, at a guess, is a phosphorus containing silver solder. It is really good. At one stage some of the famous names used to recommend it

It only has one problem: that at elevated temperature in the presence of sulphur the joint degrades. These conditions are just what you see on the flame side of a coal-fired boiler and so it is not suitable for boiler use. Most of the ME suppliers don't stock it in case it gets used on a boiler. No reason not to use it one other bits tho'

Cheers!