Heat-Tinting
Definition
Restoration by controlled heating of the polished surface. Strained metal oxidises at a different rate from unstrained metal, producing colour contrast (straw to blue temper colours) that traces the original stamp pattern.
- Method
- Controlled heating of polished metal surface
- Principle
- Strained metal oxidises faster than unstrained
- Colour range
- Straw to blue temper colours
- Application
- Restoring erased serial numbers or stamps
Common questions
Why does the original stamp pattern reappear under heat-tinting?+
Metal deformed by a die-stamped mark retains residual strain even after the visible mark is filed or ground away, and that strained metal oxidises at a measurably different rate when heated, so the colour contrast traces the original strain pattern.
What limits heat-tinting compared to chemical etching?+
Heat-tinting works best on shallow, recently erased marks, and heavy grinding that removes the full depth of strained metal can leave no pattern to recover regardless of temperature, in which case a chemical etching method is tried instead.
Related terms
- Davis Reagent
- Variant etchant for steel using cupric ammonium chloride (Cu(NH4)2Cl4) in dilute HCl. Slower acting than Fry's, sometimes preferred when contrast on Fry's...
- Fry's Reagent
- Classical etchant for plain carbon and low-alloy steel: 40 g cupric chloride (CuCl2) + 90 mL concentrated HCl + 100 mL water....
- Magnetic-Particle Method
- Non-destructive restoration for ferromagnetic metals. The polished surface is magnetised and dusted with fine iron particles; the particles cluster at the strained...
- Peak Contrast
- The narrow window during a chemical etch when the original digits are most legible. Continuing past peak contrast overetches the unstrained metal...
- Stamped Marking
- A serial, chassis, engine or part number impressed into metal by a hardened steel die under high force. The visible impression is...
- Strained Zone
- The region of cold-worked, plastically deformed metal lying beneath an original stamp. The crystal lattice is distorted, dislocation density is elevated, and...
- Villela's Reagent
- Etchant for stainless and high-chromium steels: 1 g picric acid + 5 mL concentrated HCl + 100 mL ethanol. Targets prior austenite...