# Black Light Applications Guide: Forensics, Stains, Currency, HVAC & NDT

> Author: Black Light Encyclopedia Research Group
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## 1. Forensic Latent Fluid Detection
- Target: Semen, vaginal fluids, saliva, concentrated urine.
- Optimal Wavelength: 365 nm UV-A (or 450 nm ALS with 550nm orange barrier goggles).
- Mechanism: Natural auto-fluorescence of endogenous flavins and choline/protein conjugates. Semen fluoresces bright blue-white to yellowish-green. Blood does NOT fluoresce (absorbs UV, appearing black).

## 2. Banknote Counterfeit Verification
- US Banknote Security Thread Colors (365 nm):
  • $5 bill: Fluoresces bright BLUE (left of portrait)
  • $10 bill: Fluoresces bright ORANGE (right of portrait)
  • $20 bill: Fluoresces bright GREEN (far left)
  • $50 bill: Fluoresces bright YELLOW (right of portrait)
  • $100 bill: Fluoresces bright PINK/RED (left of portrait)
- Authentic paper is cotton/linen with NO background fluorescence. Counterfeits glow solid blue.

## 3. Pet Urine Detection
- Target: Dried urea, urobilin, and uric acid crystals.
- Optimal Wavelength: 365 nm with black ZWB2 filter.
- Stains glow dull mustard-yellow. Commercial laundry detergents glow electric cyan-blue due to stilbene optical brighteners. 395nm flashlights fail due to visible purple glare.

## 4. HVAC & Automotive Leak Detection
- Target: Refrigerant compressor oil (POE/PAG) mixed with fluorescent tracing dye.
- Standard: SAE J2297. Reveals micro-leaks as small as 0.1 oz/year with brilliant chartreuse glow.

## 5. Art, Antique & Glass Authentication
- Uranium/Vaseline Glass: 0.1%–2% UO2 exhibits vivid neon green fluorescence under 365nm and 395nm.
- Oil Paintings: Aged varnish fluoresces greenish-yellow. Modern inpainting/repairs appear jet-black voids.
- Porcelain: Original glaze does not fluoresce; modern repair resins glow bright blue-violet.

## 6. Industrial NDT (FPI & MPI)
- Aerospace Standard: ASTM E1417 (FPI) and ASTM E1444 (MPI). Requires 365nm ± 5nm, >=1,000 µW/cm² irradiance, <20 lux ambient visible light.