A solder joint can make a carefully cut panel look crisp and deliberate, or leave it looking lumpy, scorched and difficult to finish. If you are asking which solder for stained glass to use, start with the construction method rather than the glass itself. Copper foil work, lead came work and small repair jobs each ask slightly different things of the solder.
For most traditional stained glass work, 50/50 and 60/40 tin-lead solder are the dependable workshop choices. The numbers refer to the proportion of tin and lead in the alloy. More tin generally gives a brighter finish and a smoother, more raised bead; more lead produces a slightly duller, flatter joint. Neither is universally better. The right choice is the one that suits the way the piece is built and the finish you want to achieve.
Which solder for stained glass: the short answer
Use 60/40 solder for most copper foil panels, sun catchers and decorative soldered seams. It flows well and builds a pleasing rounded bead over properly foiled and fluxed joins.
Use 50/50 solder for most lead came work. It creates a sound, practical joint at lead intersections without building excessive bulk. It is also useful for copper foil work when you prefer a less pronounced seam or are assembling a larger, more structural piece.
Use 63/37 solder when you want very predictable flow and a fast-setting joint, particularly for small detailed work, tacking or repairs. It can be excellent in experienced hands, but it is not essential as a first solder for every stained glass project.
The three alloys will all solder stained glass successfully. Good fit-up, clean foil or came, suitable flux and controlled iron temperature matter just as much as the number stamped on the solder.
60/40 solder for copper foil work
60/40 solder contains 60 per cent tin and 40 per cent lead. It has a relatively narrow melting range, so it moves from solid to liquid smoothly and is easy to draw along a foiled seam. This is why it is such a familiar choice for Tiffany-style copper foil work.
When used with even foil application and a suitable liquid flux, 60/40 can form the rounded, continuous bead many makers want on lamp shades, panels and hanging pieces. It is forgiving enough for beginners, while still giving experienced makers control over the height and shape of the bead.
There is a trade-off. Because 60/40 flows readily, an iron that is too hot or held in one place for too long can pull solder away from a join, flood a tight corner or overheat delicate glass. Keep the work supported on a flat, heat-safe surface and move the iron steadily. Let the solder follow the heat rather than trying to push a cold blob around with the tip.
For a neat finish, tack the entire project first, then solder one face fully before turning it over. On larger pieces, alternate between areas rather than concentrating heat in one section. This reduces stress on the glass and helps prevent the panel from becoming distorted.
When 60/40 is not the best fit
If you are soldering lead came intersections, 60/40 can leave a more noticeable mound than necessary. It is not wrong to use it, especially for a small project, but 50/50 is usually the more traditional and practical choice. Likewise, if you want a deliberately flatter foil seam, 50/50 may give you more of the finish you are after.
50/50 solder for lead came panels
50/50 solder contains equal parts tin and lead. It has a wider melting range than 60/40, which means it remains workable over a broader temperature range before it fully flows. In leadlighting, that characteristic is useful: it allows the solder to bond the came intersection without racing across the surface or building an overly high bead.
A well-made lead came joint should look tidy, cover the intersection properly and remain modest in profile. The aim is not a decorative ridge of solder. It is a secure join that will sit comfortably beneath cement and finishing compound once the panel is waterproofed and strengthened.
For lead came work, apply flux only where it is needed, heat the joint briefly and feed in enough solder to bridge the intersection. If the solder sits on top in a dull lump, the metal is probably not clean enough or has not reached the right temperature. If it disappears into the joint or runs down the came, you have likely used too much heat, too much flux or too much solder.
50/50 is also a sensible all-rounder for makers who work across both lead came and copper foil methods. Its finish is generally flatter than 60/40, but it is reliable and strong when the joint preparation is sound.
Where 63/37 solder earns its place
63/37 solder is often called eutectic solder. At 183°C, it changes from solid to liquid without passing through the same pasty stage as 50/50 or 60/40. In practical terms, it sets quickly and can give a clean, controlled joint when your iron temperature and technique are consistent.
This makes 63/37 useful for fine copper foil details, small decorative additions, tacking pieces in place and repairs where you do not want to reheat surrounding seams for long. It can also reduce the chance of a joint shifting while it cools.
Its fast set can be less forgiving for a beginner learning how to shape a bead. If your movement is hesitant, it may leave joins that look segmented rather than flowing. For that reason, many makers keep 60/40 as their primary copper foil solder and use 63/37 for particular jobs rather than every seam.
Avoid solder that is made for another trade
Not every solder labelled for metalwork belongs on a stained glass bench. Plumbing solder may have an unsuitable alloy, while solder with an acid core or rosin core is designed for different applications. Stained glass solder is generally solid wire or bar solder used with a separate flux chosen for copper foil or lead came.
Lead-free solder is sometimes requested for projects where lead handling is a concern. It can be appropriate in specific situations, but it usually requires more heat and behaves differently from traditional tin-lead alloys. That extra heat can make copper foil work harder to control and may be less kind to came, glass and nearby soldered seams. Choose a lead-free alloy specifically intended for stained glass, and expect to adjust your technique rather than treating it as a direct swap.
Silver-bearing solder is another specialist option, not a default choice for standard stained glass construction. It costs more and is generally selected for a particular technical reason, such as joining certain metals, rather than for ordinary foil or lead came seams.
The finish depends on more than the alloy
A poor solder finish is often blamed on the wrong alloy when the real issue is preparation. Copper foil must be burnished firmly to the glass, with clean overlaps and no lifting edges. Lead came needs bright, clean contact points. Old oxidation, cutting oil, fingerprints and residue can all interfere with solder flow.
Flux is equally important. Use it sparingly but thoroughly on the area to be soldered, then clean the completed work well. Flux residue is corrosive and will continue to affect the metal if left behind. This is particularly relevant before applying black patina, copper patina or a final polish, as residue can cause patchy or disappointing results.
Iron temperature matters too. A temperature-controlled iron gives the most consistent results, particularly when moving between fine foil work and heavier came. The correct setting depends on your iron, tip size, solder and the mass of the work, so test on offcuts first. You want solder to flow promptly after contact, not hiss aggressively, burn the flux or sit lifelessly on the surface.
Choose the solder in a practical order
For a first copper foil project, begin with 60/40 solder and concentrate on clean foil, light flux application and steady iron movement. For a traditional lead came panel, choose 50/50 solder and practise creating compact joints at came intersections. Once you are comfortable reading how solder behaves under the iron, 63/37 becomes a useful addition for detailed or precise work.
Keep your solder labelled and stored cleanly, especially if you use more than one alloy in the studio. Most importantly, treat lead-containing solder with appropriate care: work in a ventilated area, avoid eating or drinking at the bench, wash hands thoroughly after soldering, and collect offcuts rather than allowing them into general rubbish.
The best solder is the one that supports the construction method and lets your workmanship show. Start with 60/40 for copper foil or 50/50 for lead came, then refine your choice as your projects, preferred finish and confidence at the soldering bench develop.