Stained Glass Patina Coverage Calculator
Calculate patina solution needed for stained glass projects from solder line length and lead came type.
Returns ml for black and copper patina finishes.
What patina does for stained glass:
After soldering a stained glass panel, the solder lines are bright silver. Patina is a chemical solution that changes the color of solder to copper (copper sulfate patina) or black (black patina). This dramatically improves the appearance of the finished piece, giving it a traditional, aged look that complements the glass colors.
Patina coverage formula:
Patina volume (ml) = Solder line length (cm) × Application factor (ml/cm)
The factor already carries the bead width, because in practice you wet the bead and a little of the glass either side of it whatever its exact width. Only the application method really moves the number, and it moves it a lot: a swab uses less than half what a sponge does over the same panel.
| Application factor | Method | Notes |
|---|---|---|
| 0.05 ml/cm | Cotton swab | Most efficient, least waste, slowest |
| 0.08 ml/cm | Small brush | Good control, the usual choice |
| 0.12 ml/cm | Sponge | Quick, and you will spill some |
Solder bead width by technique, which decides how much of the panel actually changes colour:
| Technique | Typical bead width | Surface wetted per cm of line |
|---|---|---|
| Copper foil, flat | 3 to 4 mm | 0.35 cm² |
| Copper foil, beaded | 5 to 6 mm | 0.55 cm² |
| Lead came | 4 to 6 mm | 0.5 cm², but at joints only |
| Decorative overlay | 6 to 10 mm | 0.8 cm² |
Example calculation:
A 30 × 40 cm copper foil panel with 35 pieces, beaded seams, applied with a brush:
- Solder line length: 480 cm (see below)
- Both faces get patina, so 960 cm of line
- Coverage: 960 × 0.08 = 76.8 ml
- With a 20% safety margin: 92 ml, so a 4 oz bottle
Estimating solder line length. If you have not measured it, the length of every solder line on one face of a panel W by H holding n pieces is:
Line length = 2 × √(Panel area × Pieces) + W + H
For the panel above: 2 × √(1,200 × 35) + 30 + 40 = 480 cm. This is the same formula the solder weight calculator uses, so the two pages agree about the panel in front of you. Doubling it for the back is the step people forget, and it is the difference between one bottle and two.
Patina types and shelf life:
| Type | Color Result | Shelf Life | Notes |
|---|---|---|---|
| Copper sulfate | Warm copper/brown | 6–12 months | Most popular for nature themes |
| Black (selenium/tin) | Antique black | 6–12 months | Classic look, hides imperfections |
| Green (verdigris) | Green patina | 3 to 6 months | Decorative, and rare enough that it is not in the calculator |
Application tips:
- Clean solder lines thoroughly with flux remover before applying patina
- Apply patina while the piece is still slightly warm for faster reaction
- Work in small sections, rubbing with a cotton pad or brush
- Rinse with water immediately after achieving desired color
- Apply finishing wax or sealant to prevent patina from continuing to react
- Wear gloves. Patina solutions stain skin and are mildly toxic
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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