Silver Solder Problems

[gwrfan]

Hi Guys!,

I read with interest and alarm, in last week's ME Smoke Rings, about 'Solder Problems', encountered by Doug Hewson. For obvious reasons Doug doesn't mention the supplier of the questionable solder, but I would be interested, along with others I'm sure, as to where you get your silver solder? I've seen it advertised on the net, for instance, but if there is dodgy stuff around, it would be interesting to find out the best suppliers. A copper boiler in any gauge isn't cheap to construct, only to put into the 'might come in useful later' box!

Geoff, in cloudy and cool Cornwall.

[the_viffer]

One of the boilers is mine! I've a Y4 hanging around complete all but the boiler he has been making for me practically since Adam's dad was a lad.

I don't recall off-hand whether it is one or, more likely, two years over due.

If I believed in conspiracy theories I'd say it was a story to try and fob me off again.

[gwrfan]

t-v,

I see 'one of the Y4 boilers was OK', so I guess yours was the faulty one

Reminds me of when I made my Pansy boiler 20 years ago. As a complete novice, I had read what I could, done everything according to the 'book, everything was fitting ok, and all cleaned up. A member of my local club (in the Midlands) said he'd silver solder it. It took the 2 of us one day to do it, and everything seemed OK, but there were a few leaks. No matter what I did, or had someone else do, the leaks never stopped, and in fact got worse. Several different people tried to fix them, but to no avail. In the end I bought a new boiler (actually 10 years old) made by Mr short and Mr Wilson, who then lived in Devon, for what the seller paid for it, which was less than the kit of parts from Reeves! I still have the old 'new' boiler somewhere. Now I wonder if my mate's solder was from the Far East, or some such place, LOL! ;D

[greasemonkey]

HI All
I didnt know Doug was a proffesional boiler maker?!! Personally I will only buy genuine Johnsony Matthey silver solder these days and I can get that from Bruce Engineering.
This subject was mentioned on another list about 2 months ago and it was rumoured the problem may stem from the use of recycled silver in the solder. Whilst talking about Silver solder I have been told that the cadmium content has now been removed or largley reduced and so it doesnt run as well as it used to. Has anyone any experince of this as I am still using my old stock up?
Andy

[the_viffer]

If that is the case I dread to think how long the other bloke had been waiting, Geoff.

According to my records my boiler was ordered in 2003. I said before ordering I didn't mind how long it would take but I would like him to stick to whatever deadline he imposed on himself. The selected deadline was the end of 2004. Many months and maybe as much as a year ago I had the story about iffy silver solder...

Doug is a fine craftsman as is his son. You will appreciate this if you see the Southern luggage van they made for me about 5 years ago. Deadlines however are not his strong suit.

Cadmium is not nice. (It was recently discovered to be radioactive. The radioactivity is one of its least scary properties.) I'd not be surprised to find that there is pressure to be rid of it. I often use hall marking grade silver solder which has no cadmium in it and of course t'old men didn't have any cadmium in their solder. Neither cause problems. I'm not inclined to believe that any problem is due to deletion of cadmium from the solder. Any problem may be something far more subtle.

[paul]

Pardon my newbie ignorance but is Silver Bearing Solder the same as 'Silver Solder'?

[GWRdriver]

Paul,
No, it is not. While both solders are technically silver "bearing" the boiler-making variety is a high silver content brazing solder. The preferred solder for our boilers has a silver content of around 45% (the balance being copper and trace elements) and the liquidus temperatures run between 1150F and 1300F. Silver "bearing" solders as sold by DIY and plumbing supplys are conventional tin-based solders with a trace of silver, usually no more than 4%. The strength and flow temps of these solders are very little higher than if there was no silver content.

Now having said that, I will say that I have used "silver bearing" (ie 4-6% silver ) solders for steam lines and fitting connections and such which are not attached to the boiler itself with no problems.

[paul]

Thanks GWRdriver!

I used 'Silver Bearing' on my first model and it seems to be ok at present although it's only a tiny
/low pressure boiler. I've started using it on my second boiler too. Gulp! Am I likely to get enough heat from a regular blow torch (a DIY shop propane/butance cannister type) to use 'proper' silver solder?

[SteveW]

Paul,

I'm not really sure what you are using but if it's anything like the lower temperature/softer solders i.e. lead/tin/<something else> then you will have to be very careful if you intend to re-silver solder the joints.

At the temperatures needed to silver solder lead/tin solder will alloy with copper and, I'm told, melt out. Ages ago at school (and this is my only source) I was told this and had to scrape all signs of soft solder from a project before it could be silver soldered.

[paul]

Steve, I'm not really sure myself! I seem to have got through metres of solder already and I've tried all sorts (makes/types although apparently not proper silver solder). Its no great shakes as I'm only at the learning stage right now, I haven't wasted lots of money on materials. Yet!

I'll take on board what you say about low melting point solders and file them off completely if I do need to re-solder.

It's a gigantic learning curve for someone who has barely held a file in the past.

Thanks for your help

[gwrfan]

Hi Paul,

(Busy tonight aren't we? Haha). If you have used high melting point silver solder. like Easiflo, then if you have a smallish leak it is better to try, or get a 'qualified person' to try to reseal the leak using silver solder. The only problem is that in doing so, you can open up another weak point in the soldering. I believe that many leaks are caused by the joint not fluxing properly in the first instance, and when you reheat the part, you can melt flux that may be lurking in another joint! As a final attempt to put things right, you can use something like Comsol, using the correct flux, and ensuring that the area to be soldered is absolutely clean. Having used a soft solder, it is very difficult to then try and use higher melting point solders!

Geoff (with a little experience of this some years ago - and it's costly! LOL)

[greasemonkey]

Hi All
If you have used a low melting point solder containing lead, then this needs to be removed completely before you can use a high melting point silver solder, I belive this is due to the lead. If I remember correctly Mamod boilers are soft soldered together and run okay at very low pressures. What are you using for a saftey valve to prevent pressure build up? The important thing to remember about any soldering is to ensure the joint is clean and well fluxed and that you have sufficent penetration through the joint, then you shouldnt have any problems. I have just finished Silver soldering my Simplex boiler together and so far all looks okay. The regulator leaks like a sieve but the boiler seems sound so far!!!
regards

Andy

[GWRdriver]

Paul,
I can confirm the above statements, once you've begun with soft solder it is virtually impossible to follow it with silver solder unless every trace of soft solder has been removed.

Can you tell us what project (size, scale, etc) your second boiler is? Depending upon the design, size, and how far you've gone there's a chance it can be saved.

[the_viffer]

<chemistry alert>
Shesto and others sell bottles of potion which are designed to remove selectively lead based solder from metal. I don't know what is in it (but I'd like to) and I've never tried it. It might be a possibility.

</chemistry alert>

I know of a boiler which had soft solder caulking removed from it by bead blasting. As I recall it was a fairly complex operation but done as a "foreigner" in someone's lunch hour. Looked lovely when it was done.

I also know someone who runs a layer of soft solder over his fireboxes as an anti-corrosion coating. I think he must be very confident that either he'll not need to silver solder again or he can get all the soft stuff away if he needs to.

If you try and silver solder where there is soft solder even a blob picked up from the hearth then a large hole will appear in the job. Don't ask me how I know this.

[gwrfan]

We won't ask you how you know that, but now we are all curious. And no more cat jokes please, LOL!

[paul]

Right. As I've used only 'silver bearing' solder (and another general purpose soft solder) it seems like I should be ok if I can resolve a few other issues. The boiler is only 2" copper tube about 6" long - according to a book I've got ordinary solder should be ok on this sort of size when run off a couple of solid fuel tablets. To be honest I'm having enough trouble with ordinary solder without getting into the silver stuff yet (I have extremely limited space/equipment too). Thanks for the help all.

[the_viffer]

paul said:

Right. As I've used only 'silver bearing' solder (and another general purpose soft solder) it seems like I should be ok if I can resolve a few other issues. Thanks for the help all.

You can't mix silver bearing solder with silver containing hard solder. You are commited to finishing that boiler with soft solder or getting all the soft solder off it.

I don't know the strength of soft solder at elevated pressure. I'd want to find out before working the boiler. T'old men, for whom I have a great deal of admiration, used to rivet their boilers and then caulk with soft solder. I'd not want to rely on soft solder for strength personally. Probably higher up the thread I've recounted the story of Keith Wilson and the pressure gauge on the soft soldered bush. If not let me know and between cat jokes I'll fit it in.

Personally I find that silver soldering is easier than soft soldering provided you've the means for getting the job hot: the silver solder runs much better than soft.

I've said it elsewhere in this thread but I'll say it again cadmium which is in some Easiflo grades is not good for you. (Nor are the zinc fumes if you overheat but they are not as bad). Lots of ventilation is good.

[paul]

Too late I've already mixed 'em. Looks like it's curtains for this one then unless I can desolder all the bits and clean them up.

[chris vine]

Hi, Just to make your life a bit easier, the great tip with all soldering, soft and hard silver types, is to get the job hot enough for it to melt the solder itself. The flame should not be needed.
Put plenty of flux into the joint before heating and then just touch the solder into the joint and it should flow in with capilliary action.
My preference is for cutting up little bits of solder and putting them in place before heating. Then heat the metal, slightly away from the joint until the solder runs. It will always run towards the heat, even uphill.
When you get it rigth it is a pleasure and as the Viffer says, silver is really easier than soft, just as long as you have enough heat.
Chris.

[havoc]

As I've used only 'silver bearing' solder (and another general purpose soft solder) it seems like I should be ok if I can resolve a few other issues. The boiler is only 2" copper tube about 6" long - according to a book I've got ordinary solder should be ok on this sort of size when run off a couple of solid fuel tablets. To be honest I'm having enough trouble with ordinary solder without getting into the silver stuff yet (I have extremely limited space/equipment too).

This silver bearing soft solder (about 2% silver) is often used for gauge 1 these days. But it is harder than brazing with 40% silver!