How to Solder Stained Glass

Solder is an alloy with a low melting point, and the ratio on the label changes how it behaves.

60/40 is the copper foil default. Lower melting point, and it flows and self-levels, which is what makes long foil runs look uniform.

50/50 melts hotter and sets faster. It suits leaded glass, and some people lay a 50/50 base bead then top it with 60/40 because the base will not remelt and bleed through to the other side.

Lead-free (97% tin, 3% copper) is the one for anything that gets handled with bare hands - gifts, jewellery, pieces for a child's room.

The Hakko FX-601 is the copper foil pick because the temperature control sits on the handle. That matters more than it sounds: a foil run and an edge bead want different heat, and so do different solder alloys.

For leaded glass a Weller 100 watt iron is hard to beat. It heats fast and hot, so joints go quickly. On a window with 400 joints, a second or two saved per joint is 10 to 15 minutes off the job.

Buy the stand at the same time. It keeps a 400-degree iron off your bench, and it usually holds the wet sponge too.

If your iron runs at one fixed temperature, you are not stuck. A rheostat - sold as a soldering iron controller - sits between the wall and the iron and dials the power down.

It costs a fraction of a temperature-controlled iron and gives you most of the same benefit. Turn it down for delicate work and back up for a long bead.

Flux is not optional. Solder will not wet bare copper foil without it - it beads up and rolls off instead of bonding.

Gel flux is the easiest to control because it stays where you brush it rather than running across the glass.

Set up ventilation before you switch the iron on. A fume extractor is worth the money if you solder often; an open window and a fan is the minimum. Gloves and safety glasses too.

Your tip will get gunked up. That is normal, and a dirty tip is the reason a lot of beginners think their iron is faulty - oxidised tips stop transferring heat.

Wipe on a wet sponge as you work. For a deeper clean use tip tinner paste, or tin the iron on a block of sal ammoniac.

Sal ammoniac smokes hard. Get the extractor going before you touch it, and do not lean over it.

Brush flux along every foil line you are about to solder.

On a small piece you can flux the whole thing at once and work through it. On a big panel, flux a section at a time - flux dries out and stops working, and you will just be reapplying it anyway.

You will see the foil change as the flux goes on. That is what you want.

Before running full beads, drop a small blob of solder at the joints to lock the pieces in position.

Tacking first means nothing shifts while you are working, and it lets you check the layout one last time.

Big gaps between pieces are fixable without recutting. Lay small pieces of tinned wire into the void and solder over them - the solder has something to grip instead of falling through.

Feed solder onto the fluxed foil and move joint to joint rather than trying to run the whole length in one pass.

A good bead is smooth and rounded, high in the middle and tapering into the glass on both sides. Flat means not enough solder. Lumpy means the iron moved too slowly or the foil was not fluxed.

If you find it awkward feeding from the whole roll, cut a short length of solder and feed that by hand instead.

Do not lift the panel by a bead you have just run. Let it cool first.

The outside edge needs tinning on both faces before you can bead it, otherwise the edge bead has nothing to hold on to.

Textured glass takes a little more solder along the edge, because the texture lifts the foil off the surface and there is more gap to fill.

Sharp corners want smoothing into the adjacent edge. Let the area cool, pick up a drop of solder on the iron, and feed it into the corner.

Solder jump rings onto a joint, never into the middle of a foil run. A ring in the middle of a run will eventually pull away and drop the panel on the floor.

Hold the ring with pliers, heat the joint, and feed a little solder around the base.

Bead the remaining sides and the piece is ready to hang.