Laser Cleaning 1924 Evinrude Outboard Propeller

Bronze absorbs 35% of 1064 nm light — lower than steel (45%) — requiring higher average power to couple equivalent energy into the surface. The damage threshold range of 1.8–2.5 J/...

The crew inspects the rake face under magnification, then runs the pulsed 1064 nm beam across the cold-welded aluminum buildup until the pressure-welded chip spalls off the [carbide](/materials/tungsten-carbide-laser-cleaning) insert without eroding the cutting edge. Homogeneous [tool-steel](/materials/tool-steel-laser-cleaning) galling on the same die steel gets rejected because there is no absorption window to separate deposit from substrate. HEPA extraction keeps respirable aluminum dust under California's five-milligram respirable limit, and the tool goes back into the cut before built-up edge re-forms on the next pass.

The crew names the alloy and the scale before touching the beam, hot-rolled magnetite on [carbon steel](/materials/steel-laser-cleaning) needs a higher coupon band than thin GTAW heat tint on [stainless](/materials/stainless-steel-laser-cleaning), and intact Grade A mill scale is not a standard pulsed-laser-cleaning target under AMPP practice. [Titanium](/materials/titanium-laser-cleaning) alpha-case and [Inconel](/materials/inconel-laser-cleaning) service oxide each carry a different damage ceiling at 1064 nm; coupon numbers stay on those plates, not as a fleet license on every shell.

The crew Raman-scans the [copper](/materials/copper-laser-cleaning) first so they know whether they are lifting black soot and reactive chloride crust or stripping the green verdigris brochantite patina the owner wants kept. On heritage bronze they bracket pulse energy on a reference coupon and stop when cuprite still blankets the metal, because a single heavy pass melts through the noble oxide skin. HEPA capture has to beat California copper fume and patina dust limits, and anything cleaned in open air re-tarnishes unless wax or lacquer goes on before the truck leaves.

Bridge crews reach for HEPA before solvent when lead or chromate primers hide under aged topcoats, because BAAQMD cold-cleaner rules cap stripper VOC well below what commercial products carry. A pulsed 1064 nm pass removes organic films without a liquid hazmat stream, yet [oak](/materials/oak-laser-cleaning) and [concrete](/materials/concrete-laser-cleaning) test coupons on the same job do not inherit plate-[steel](/materials/steel-laser-cleaning) damage margins. Grit-profile recoats that demand ISO 8503 anchor tooth stay out of scope even when the visible coat is gone.

Black crust on heritage stone will not come off safely until the crew knows whether they are facing gypsum sulphation, a biofilm, or salt efflorescence beneath the dark layer. Fluence that clears gypsum crust on [marble](/materials/marble-laser-cleaning) can overheat porous [sandstone](/materials/sandstone-laser-cleaning) where the sandstone coupon crust margin at 1064 nm is only about 0.4 J/cm².

Exterior cleaning of San Francisco City Landmarks and Mills Act properties must satisfy the Secretary of the Interior's Standards. The "gentlest means possible" mandate under 36 CF...

Contaminated optics and precision surfaces fail. Coating delamination starts when LIDT drops. LIDT is the power level at which optical coatings fail. It drops measurably at just 6...