How To Read Mica "Domino" Capacitors
Vintage Capacitor Color Code Guide
Mica dot codes & bumblebee band codes — calculate any antique capacitor
How Capacitor Color Codes Work
Vintage capacitors use colored dots or bands to indicate capacitance in picofarads (pF). Mica capacitors use dots pressed into Bakelite; “bumblebee” paper/oil capacitors use colored bands on a cylindrical body. The 6-dot “domino” mica reads:
- Dot A — capacitor type (JAN, EIA, or molded paper)
- Dots B, C — two significant figures of the capacitance value
- Dot D — decimal multiplier (number of zeros)
- Dot E — capacitance tolerance (color number = %)
- Dot F — characteristic class (temperature coefficient)
Hold the capacitor with the manufacturer name right-side up, then read left to right across the top row, then right to left across the bottom row. Bumblebee capacitors use six bands: two significant digits, multiplier, tolerance, and two voltage digits (combined × 100 for working voltage). The end with a band closer to the edge marks the outside foil. Gold and silver multipliers give fractional values (0.1 and 0.01 pF respectively).
Color Code Reference
| Color | Sig. Fig. | Multiplier | Tolerance | DC Voltage |
|---|---|---|---|---|
| Black | 0 | 1 | — | — |
| Brown | 1 | 10 | ±1% | 100V |
| Red | 2 | 100 | ±2% | 200V |
| Orange | 3 | 1,000 | ±3% | 300V |
| Yellow | 4 | 10,000 | ±4% | 400V |
| Green | 5 | 100,000 | ±5% | 500V |
| Blue | 6 | 1,000,000 | ±6% | 600V |
| Violet | 7 | 10,000,000 | ±7% | 700V |
| Gray | 8 | 100,000,000 | ±8% | 800V |
| White | 9 | 1,000,000,000 | ±9% | 900V |
| Gold | — | 0.1 | ±5% | 1000V |
| Silver | — | 0.01 | ±10% | 2000V |
| None | — | — | ±20% | 500V |
Style 1: Three-Dot Mica (RMA / Pre-WWII)
The simplest vintage mica capacitor code. Dots A and B give two significant figures, dot C is the decimal multiplier. No tolerance marking — assume ±20%.
Style 2: Four-Dot Mica (RMA)
Four dots add a tolerance marking. Dots A and B give two significant figures, dot C is the decimal multiplier, dot D is the capacitance tolerance.
Style 3: Six-Dot “Domino” Mica (JAN / EIA)
Hold the capacitor with the manufacturer name right-side up, then read left to right. Top row gives the type and two significant figures. Bottom row (read right to left) gives the multiplier, tolerance, and characteristic class.
Style 4: “Bumblebee” Paper/Oil Capacitor
Cylindrical paper-in-oil capacitors with colored bands, common in 1940s–1960s tube equipment. Six bands give two significant digits, a multiplier, tolerance, and a two-digit working voltage (×100). The end with a band closer to the edge marks the outside foil — connect that end to ground or the low-impedance side of the circuit.
Capacitor Value Converter
Convert a capacitance value between picofarads (pF), nanofarads (nF), and microfarads (µF).
Notes for Collectors
pF = picofarads. nF = nanofarads (1 nF = 1,000 pF). µF = microfarads (1 µF = 1,000,000 pF). Capacitor values are always read in picofarads from the color code.
Silver mica capacitors are exceptionally stable and were widely used in RF and IF circuits where precision mattered. If a vintage mica reads open or leaky, it should be replaced — they rarely drift but can fail with age. The phenolic casing can crack, so handle old mica caps gently.
“Bumblebee” paper/oil capacitors are cylindrical capacitors with colored bands. They are known for moisture ingress and value drift — always test before reinstalling in a restoration. The end with a band closest to the edge marks the outside foil, which should be connected to ground or the low-impedance side of the circuit.