Silver Solder - which one?

Good silver solder for steam engine work is 96% tin, 4% silver. It has melt point of around 430 deg. I think. Harris Stay-Bright is a common brand.. Technically it is known as "silver bearing solder", I suppose because of the relatively low silver content. It is used with zinc chloride / hydrochloric acid flux, sold by Harris as "Stay Clean". PM Research specifies this type of silver solder in their boiler kits - I recently built one. I'm not sure about the "official" silver solder for jewelry work but 96/4 silver bearing solder has worked well for minor jewelry repairs I have made. Incidentally,

96/4 is sold by Radio Shack as silver bearing solder.

The higher temp stuff, 800 degrees and higher is known as silver braze. It is typically of high silver content, ranging upwards to 45% silver. Costly! It is very strong - weld strength - probably wasted strength for jewelry work though. Besides the higher temp would make it harder to handle without damage to the jewelry.

Bob Swinney

Hard, medium and easy refers to melting temperature, hard being the highest.

In jewellry work, color match is more important than strength. That influences the choice of alloys, depending on what metals are to be joined.

For general purpose silverbrazing of steel, stainless and brass I like a cadmium-bearing 45% silver alloy like Handy Harman EasyFlo 45. It wets and flows very nicely. It's hard to find cad-bearing alloys in retail welding stores because cadmium fumes are bad (don't breath the fumes, have good ventilation, duh!) and Americans are litigious, but it is widely-used in industry and by bicycle framebuilders. A reasonably good substitute is a 56% silver non-cad-bearing alloy like Harris-Welco Safety-Silv 56 which I think can be found at Mnpls Oxygen and Toll. These materials have a significant copper content which gives a color closer to polished brass than to silver. They are very strong.

Check Reynolds Welding just north of Hwy 7 ; they might have some interesting choices.

I like the Harris products. I think the fluxes I use are Sta-Silv white (for general soldering, it's probably just zinc chloride) and black.

It appears that Harris no longer makes cadmium-bearing silver brazing alloys. I think mine was made by Engelhardt. I think I use the 45% silver type.

I use the white flux on small stuff that heats up really quickly, and the black hi-temp flux when I'm doing more robust steel parts. I never had any luck at all silver soldering until I started using an oxy-acetylene welding torch. Nothing but a messy discouragement.

Grant

Stay-Brite is good stuff, but silver brazing is about 5X stronger. Stay-Brite does give a nice colormatch with stainless. Brownell's offers a silverbrazing alloy they say is a good colormatch with stainless. I haven't tried it.

There are two flavors of StayBrite: the regular stuff and StayBrite

1. Regular StayBrite is very fluid, almost like water. StayBrite 8 has a plastic range so it is possible to get some buildup if desired.

One troy ounce of real silversolder (several feet of 1/16" dia) will make a lot of joints!

Ordinary soldering tools (irons, propane or butane torch) are fine with StayBrite. You need oxy-fuel for silver-brazing. I really like the Meco Midget torch running oxy-acetylene.

This inexpensive torch may look like a toy, but I can assure you it definitely does not work like a toy. It is an excellent tool. It's the torch I use 90% of the time for silverbrazing and for welding thin aluminum.

The Smith Little Torch is better for very small work, as in jewellry. The Meco Midget #0 tip is about equivalent to a Litttle Torch #4 tip.

John -

I think most have missed the boat - this is Model Steam engine - Not jewelry.

I'd use the copper silver hard brazing silver solders. Pressure and stress requires these.

Martin

Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder

John Hofstad-Parkhill wrote:

stress requires these.

Yep!

Harold

Judging by the responses you've had it seems to me that there is a terminology problem here. I reckon your documentation originated in UK where silver solder is the name given to a hard solder which is an alloy of copper, silver and other metals. It has a melting point of around 600C or more and is comparable in strength to brazing brass. It is _not_ the same as the lead bearing solders that can be melted with a soldering iron. The proper (UK type) silver solder needs a torch to melt it - you can use air/propane or air/butane, but oxy/propane is also used. You also need a special flux. The hallmarking quality silver solder used for jewellery is a similar product, but has rather more silver in the alloy and is, consequently, more expensive. The hard/medium/soft refers to the melting points, but even soft melts at around 600C or more. Definitely not soldering iron territory.

There are several.

First of all, the older recipes included cadmium. This is great (metallurgically) but it's toxic as anything. So schools ditched all their cadmium silver solder a few years back - eBay bargains are still to be had ! Incidentally the flux is nasty too.

Secondly, there are different grades, with different melting points. If you're doing boiler work then you often need to use several of these in turn, so that lower temperatures ("softer") don't melt the joints you made earlier with the harder solders.

In general, use the hardest silver solder you can get away with. Less silver, so it's cheaper. Low temperature or colour considerations might force you to a lowertem perature one.

1. Gary Wooding Jan 14, 3:32 am show options

Newsgroups: rec.crafts.metalworking From: Gary Wooding - Find messages by this author Date: Sat, 14 Jan 2006 08:32:52 +0000 Local: Sat, Jan 14 2006 3:32 am Subject: Re: Silver Solder - which one? Reply | Reply to Author | Forward | Print | Individual Message | Show original | Report Abuse

John Hofstad-Parkhill wrote:

Judging by the responses you've had it seems to me that there is a terminology problem here. I reckon your documentation originated in UK where silver solder is the

name given to a hard solder which is an alloy of copper, silver and other metals. It has a melting point of around 600C or more and is comparable in strength to brazing brass. It is _not_ the same as the lead bearing solders that can be melted with a soldering iron. The proper (UK type) silver solder needs a torch to melt it - you can use air/propane or air/butane, but oxy/propane is also used. You also need a special flux. The hallmarking quality silver solder used for jewellery is a similar product, but has rather more silver in the alloy and is, consequently, more expensive. The hard/medium/soft refers to the melting points, but even soft melts at around 600C or more. Definitely not soldering iron territory.

I beg to differ with your terminology. Soldering, by definition, is a bonding alloy that melts at a lower temperature then the base metal. Hard solders melt at brazing temperatures, soft solders generally below

600 degrees F. Jewelers silver solder comes in hard, medium and easy grades to allow consecutive jointing operations on intricate pieces. Bugs

I make no comment on suitability of any alloy or method for boiler work, however oxy-fuel is not usually required for generic silver brazing. For non-silver alloys you may need it, but for something like classic 56% silver (non-cadmium) wire on small or thin-wall parts, you do not.

The jewelry industry standardly uses acetylene-available air. For very fine parts a cheap bottle-top propane torch will just barely work, while a swirl-flame (retail store) plumbing torch will put out plenty of heat. The advantage of the jewelry-style acetylene (still burning in atmosphere) torch is that you can concentrate the heat more than with the swirl-flame plumbing torch. However for occasional use it's better to have something that can work on a small retail cylinder than to have to buy and store an acetylene cylinder - and there's always MAPP if propane isn't hot enough.

My guess is that if the poster has the jewelry setup, simply buying a larger torch tip (such as might be used for melting) would be sufficient to adapt to the larger workpieces. But a nice self-igniting swirl flame bottle torch is a handy thing to have around anyway (I used mine on an adapter hose from a grill tank to anneal trumpet bell blanks, even after I started using acetylene for a fine flame and higher heat to support a higher-brass alloy when brazing the bell tail)

All solder used in the jewelry industry to solder jewlery is "hard" solder, i.e. it does not contain tin.

The terms we use, hard, medium, easy are really misleading. More appropriate might be high, medium, low as refering to the temperatures at which they flow.

I have marked my solders 1, 2, and 3 as in work flow, where my number 1 solder is used first in the process, and has the highest flow tempreature (hard). Number 2 is medium, and #3 is easy.

For silver I have 4 different solders. Again, these are all hard solders and do not contain tin.

In case of the boiler for instance for your steam engine, i would use the highest temparature solder that the metal you are soldering would allow. I assume you are making the boiler out of copper. That can be soldered with a "hard" of "medium" silver solder. I would not use a tin based solder as one of the posters has suggested, especailly for a boiler.

Not waste at all, and required by law.

For you maybe, not for a goldsmith who knows what he/she is doing. I haven't damaged a piece of silver jewelry, by soldering it with silver solder, in more than 25 years.

Not true. Acetylene torches are rarely used in the jewelry industry. It is to dirty and too hot for most jewelry work.

With all due respect, you don't know what you are talking about.

I have used a mouth blown and/or bellows blown propane torch for the last 30 years. Not a problem with fine work at all.

Plumbing torch for jewelry, ... cute.

Propane with air is plenty hot, and propane with oxygen, which I use for platinum work is hot enough to melt platinum.

Finally someone who knows what he is talking about.

Soldering a boiler with tin based solder, as someone suggested, ... yeah right. Boooom!

My "hard" (#1 high temperature flowing) silver solder melts at 860 degrees C. I got it from Degussa in Germany. I also get solders from Hafner in Germany.

Thank you.

I certainly defer to your experience in the area of jewellry making. Propane-air particularly forced air, definitely does have ample heat and temperature for brazing and even melting -- with enough air, enough propane and enough time.

However, even a small boiler is a lot bigger heatsink than a piece of jewellry, so a pinpoint air-fuel flame is not gonna do it. It would take an air-fuel flame large enough for the job. That flame will be considerably larger and more diffuse than an O/A or oxy-propane flame of compararable capability.

My experience (which does not include jewellry) is that I prefer oxy-acetylene for the speed and control that it affords. YMMV, of course. I don't need to use or stock three different meltingpoint materials to make multiple joints in a single piece because I can control the heat well enough to not melt previous joints. The fact that the pieces I work with are larger than jewellry undoubtedly helps. I can also locally focus the heat to draw the alloy where I want it to go: the molten material "follows the heat".

I've invited John to come over and try my O/A rigs, and I'll give his acetylene-air (aspirated, not forced) a try as well, having a fair amount of experience in silverbrazing. I have little doubt that we will able to make joints with any of the various tools.

Would it hold enough pressure to make a decent boom, or more like phffffffft! Gerry :-)} London, Canada