Stained Glass Zinc Came Calculator

What is zinc came?

Came (pronounced “kaim”) is the metal channel that holds pieces of glass together in a stained glass panel. Zinc came is a rigid, strong alternative to traditional lead came. It is commonly used for the outer border of a panel because it provides structural rigidity, and sometimes for straight interior lines.

Zinc came vs. lead came:

Came length calculation:

For a stained glass panel, you need:

1. Border came (zinc): The perimeter of the panel
2. Interior came (lead or zinc): All the lines between glass pieces

Border came = 2 × (Panel width + Panel height) + 6" waste

Interior came = Sum of all interior cut line lengths + 10% waste

Estimating interior lines:

You do not need to measure every line. For n roughly equal pieces in a panel W by H, the total length of all the lines including the outer edges is 2 × √(W × H × n) + W + H. Take the border off that and the interior alone is:

Interior came ≈ 2 × √(Panel area × Pieces) − (Width + Height)

Note what this depends on. Per-piece rules of thumb (“about 6 inches of came per piece”) only hold for one panel size, because doubling the panel while keeping the piece count doubles the length of every line. This formula uses the panel size you actually entered.

Curved pieces then need a little more, since a wandering outline is longer than a straight one enclosing the same area. The complexity setting adds nothing for straight geometric work, about 12% for mixed shapes and 25% for tight curves.

Worked example:

A 24" × 18" panel with 35 glass pieces, mixed shapes:

• Border (zinc): 2 × (24 + 18) + 6 = 90 inches (7.5 feet)
• Interior: 2 × √(432 × 35) − 42 = 246 − 42 = 204 inches, and 12% more for mixed shapes = 228 inches
• Interior with 10% waste: 228 × 1.10 = 251 inches (20.9 feet)
• Came comes in 6-foot strips, so the border takes 90 ÷ 72 = 2 strips and the interior 4

Profile selection:

• 1/4" U-channel: Thin border, delicate look
• 3/8" U-channel: Standard border, good balance of strength and appearance
• 1/2" U-channel: Heavy panels, extra strength
• The “U” channel is for borders (one side exposed). “H” channel is for interior lines (glass on both sides).

Zinc came preparation:

Zinc has to be cleaned and fluxed before soldering. Unlike lead it grows a stubborn oxide layer, and solder simply will not stick to a dirty surface. Use oleic acid or a zinc-specific flux, and file or sand the zinc at each joint. This is the step beginners skip, and the result is a joint that looks soldered and pulls apart the first time the panel is lifted.

How much solder. Came panels take far less solder than foiled ones, because nothing runs along the line. You only solder where came meets came. A grid of n pieces has roughly n + (W + H) × √(n ÷ area) − 3 of those crossings, and each takes about a gram a side. A 24 × 18 inch panel with 35 pieces works out to about 44 joints and 88 grams, against several hundred grams for the same panel done in copper foil.

Structural note: For panels over 4 square feet, run zinc reinforcing bars across the back so no unsupported span exceeds about 18 inches, and solder them to the came joints they cross. Without them a panel bows out of plane within a year or two, and once it has bowed you cannot flatten it.