When I was first interested in learning to solder silver, I was very intimidated by the scope of the endeavor not to mention the flame. So I started very small with few expectations about the results. My biggest tip for the novice is to not expect it to go the way you think it should. Take your time and learn what it will actually do and not do. Be prepared to melt things beyond repair. You learn your best lessons from your worst mistakes.
For my first modest foray into silver soldering, I bought: a butane powered mini-torch; a magnesia soldering block; easy solder in wire form; a few 18 gauge, open jump rings (8 or 9mm are easiest to handle at first); pickle; copper tongs and flux. You will also need a jar of water for quenching, safety goggles, a pair of heatless tweezers and a pair of wire cutters. Always wear safety goggles.
To begin, set your magnesia block (I prefer these to charcoal because of the lesser cost, they take less time to heat and they cool faster) in an open area with nothing flammable around it. Push back your sleeves if they are long and tie back your hair as well, if it is long. It is a good idea to familiarize yourself with the operation of the torch before soldering your first jump ring. Turn it on and off several times until you can do it easily.
Take a clean jump ring and make certain that the ends line up exactly and that they are touching each other. Solder will make a join solid, but it will not fill gaps. Apply flux to the place you want to join. When the solder melts it will follow the flame and flow where the flux is. Do not put flux anywhere you do not want the solder to go.
A few words about fluxes are in order. There are a lot to choose from. I use either a paste flux or a liquid flux depending on what I want to do. Flux has two purposes; to help the solder flow and to help protect your silver from firescale. When you heat your sterling to soldering temperatures, you bring some of the copper in the alloy (92.5% silver, 7.5% copper) to the surface. The copper is essentially what makes sterling silver tarnish so rapidly and is responsible for the firescale. Firescale shows itself as a black coating on the surface of your sterling. A number of “how-to’s” on silver soldering will tell you to flux the entire piece in order to limit the firescale. But this sometimes makes the solder go where you do not want it and it is not always fun trying to remove the solder later. Paste flux stays where you put it and liquid does not always stay put. But paste flux can become very hard and glassy after heating and requires more time in the pickle to eliminate it all. You really will not have a problem with your first jump ring soldering project and may use any type of flux that you like, but these are a few things to remember for later; if there is a later. I caught the “bug” right off and haven’t regretted it.
Now, take your wire cutters and cut off a small piece of easy solder. About an 1/8 of an inch should be more than enough. Place the solder on the magnesia block. Place the join of the jump ring on top of the solder so that it forms a cross. Turn off any direct lighting on your work area and use only room lighting. Light your torch. Bring the torch slowly closer to the jump ring so as not to blow the jump ring off of the solder.
If you are using a paste flux and you set the jump ring quickly down upon the solder, you can let it dry a bit and the two will stick together. If you are using a liquid flux, do as I recommended in the previous paragraph.
By not brightly illuminating your work, you will be better able to see the changes in color of the flux and the metal as it heats. Learning about these color changes now will help you later when you make larger projects.
When the area of the magnesia block that the jump ring is resting on and the jump ring and solder reach the melting point of the solder, the solder will flow. Move the flame around the circumference of the jump ring. As you see it start to turn pinkish, concentrate the flame mostly on the join. You will see the jump ring drop level onto the surface of the block and you will see the solder become very shiny and flow up the join. You will have to look quick for that last part. Remove the flame as soon as you see those two things happen. Leave the flame too long and you will melt your jump ring into a nice ball. When I first made this error, I then had a lot of fun making balls from scrap silver. They can be useful in some designs. Also, remember that the solder will follow the flame, so take the flame away straight up; not sideways. Otherwise, the solder will follow the flame over the jump ring and coat part of your ring.
A quick word about heat sinks. Everything your work touches soaks up the heat of the flame and takes it away from your work; including the air in the room. Never try to solder anything large together by dangling it in the air. I know one person who tried this and failed. You can not (and do not want to) heat all the air in your work room to soldering temperatures. Small items like jump rings or finger rings work fairly well, though.
Pick up the jump ring with the heatless tweezers and dunk it in the quenching water. It will hiss and spit a bit. Dry the jump ring and inspect the join. A small lump at the join is acceptable. A large lump is not, unless you want to make it a design element. Ideally, the joined place should not be obvious. It will take some experimentation with the different gauges of wire and amounts of solder to get to the point where you can make a nearly invisible join.
Take your copper tongs and place the jump ring in the pickle solution. Pickle is basically a week acid that will turn the copper firescale into a white coating that can be easily polished off. Do not drop it into the pickle. Also, do not put it in the pickle if it is still quite hot. Even though it is a relatively weak acid, it will still burn you and put holes in your clothes. Not immediately, though. They tend to show up after you wash them. You must use copper tongs because any ferrous (iron bearing) metal that comes in contact with the solution will electrolyze it and you will end up plating copper onto your silver. Remove the jump ring with the copper tongs also. Rinse Solder Paste it well in your quenching water. Or have a jar of water with baking soda added to it standing by to completely neutralize the acid.
If you do not want a hard, bright, shiny polish on your jump rings, you can use a brass brush to remove the white coating. Dip a soft brass brush in a solution of dish soap and water and thoroughly rub the jump ring. The soap keeps brass from depositing on the silver. If you want a bright shine, you will have to use a buffing wheel of some sort charged with a polishing compound. Only a very aggressive polishing compound will remove firescale. If you do not pickle your silver long enough, then you can try a bobbing compound. But remember, this will remove more of the silver and if you have surface detail, you will lose some or all ot it. It really is best to pickle your item long enough that no hint (a yellowish color) of firescale remains.