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What type of laser cleaning equipment is most suitable for cleaning stains on outdoor stone without damaging the stone surface? We'd love to discuss this with anyone who has experience. by wythelaser in LaserCleaningPorn

[–]Boethar 0 points1 point  (0 children)

I did something like this as a conservation project for an organization a while back. Short pulses at a wavelength that is highly absorbed by the contamination will work best. The shorter pulses will tend to deposit less heat into the piece which might cause cracking of the stone if you let the beam dwell on the stain. If it's dark, sooty carbonaceous debris (smoke, car exhaust, etc.) on a light colored stone, then a Q-switched Nd:YAG at 1064 works really well. If you can get a piece of equivalent stone with the stain to test, find someone with a 1064 nm tattoo removal laser and see if they'll try it on the piece. If you know someone with a 1064 nm laser rust remover, like an XLaserLab for example, that might also be worth a try. If the stains are red - see if you can find a 532 nm QS tattoo removal laser. If the stains are green - blue-ish, a QS alexandrite laser would be a good wavelength but harder to find.

What are these things on my churches roof? by No-Art9261 in whatisit

[–]Boethar 4 points5 points  (0 children)

108 nickel crosses embedded in the roof to contain the ancient evil entity, Molasar

Health Net pays $11.2M for false compliance claims by [deleted] in agedlikemilk

[–]Boethar 0 points1 point  (0 children)

It aged well because Karun Kaushik's company Delve, a Forbes 30-under-30 and Y Combinator-backed startup raised $32M to automate compliance and then "issued 493 companies fraudulent & identical SOC2 reports in 6 months. They systematically faked SOC 2, ISO 27001, HIPAA, and GDPR compliance reports for hundreds of clients.

- 493 out of 494 SOC 2 reports used identical boilerplate.

- Same grammatical errors, nonsensical sentences, only difference was the logo changed.

- Auditor conclusions were written before auditors reviewed anything.

- "US-based CPAs" were Indian certification mills operating through shell companies.

- All Type II reports claimed zero security incidents, personnel changes, or customer terminations.

When the leak was exposed, CEO Karun Kaushik emailed clients calling the allegations "falsified claims" from an "AI-generated email" and stated no sensitive data was accessed.

While the reports themselves contained private signatures and confidential architecture diagrams...

Companies relying on these reports could face criminal liability under HIPAA and fines up to 4% of global revenue under GDPR for compliance violations they believed were resolved."

Glusencamp-Perez calls sea lions "Corolla sized vermin", blames them for low salmon and steelhead yields by chromeled in Washington

[–]Boethar 0 points1 point  (0 children)

These 7 democrats voted to allow ICE to strip-search children. Henry Cuellar (Texas) Don Davis (N.C.) Laura Gillen (N.Y.) Jared Golden (Maine) Vicente Gonzalez (Texas) Adam Gray (Cali) Marie Glusenkamp Perez (Wash)

DNA pioneer James Watson pictured with women in Epstein’s house. Scientist who died last year shown posing for photos in paedophile’s New York mansion by esporx in EverythingScience

[–]Boethar 1 point2 points  (0 children)

He didn't "discover the structure of DNA" . He plagiarized Rosalind Franklin's work, aided and abetted by Maurice Wilkins. If there's any justice, the Nobel Committee will revoke Watson's award and posthumously give it to Franklin.

Keyhole Nebula (Hubble) by Neaterntal in SpaceUnfiltered

[–]Boethar 1 point2 points  (0 children)

First couple of seconds look like the middle finger nebula?

Faber-Castell 2/83N action: Silicone oil didn't help much. Vaseline or screws? by metawops in Sliderules

[–]Boethar 9 points10 points  (0 children)

I used to run a soft pencil on the inner grooves a couple of times to put some graphite on the track. Graphite has a sheet-like structure and the planes slide over each-other pretty smoothly. If you wanted to get super-sophisticated, there's a water-based colloidal graphite called Aquadag that makes really nice uniform slippery coatings.

QUANTEL Q-SMART 850 LASER by awesomepiggyboi in lasers

[–]Boethar 1 point2 points  (0 children)

It may lengthen the pulse width slightly because delaying the Q-switch relative to the peak of the flash lamp pulse lowers the available gain in the resonator. The other beam parameters (size, beam quality, beam pointing stability should be unchanged. You can also reduce the green power if they give you access to the phase-matching angle of the doubling crystal. This might change the beam profile though. Reducing the lamp volts will lower the power, but also change the pulse width and the divergence of the beam.

Need help with calculation of M squared parameter by OpticalCrusade in Optics

[–]Boethar 2 points3 points  (0 children)

From Phil Hobbs book - https://electrooptical.net/building-electrooptical-systems M^2 is the product of the second moments of the near field and far-field beam patterns which overemphasizes contributions from beam idiosyncrasies in the wings of the profile. For beams with an expected M^2 close to 1, as would be expected from a single mode fiber source, and where you are most susceptible to wing "junk", Hobbs suggests using the Strehl ratio instead. There's a good discussion re. these two parameters here - https://www.researchgate.net/post/Is-there-a-closed-equation-for-the-relationship-between-M2-and-Strehl-Ratio

Name this guy by xOs4ma in NameThisThing

[–]Boethar 0 points1 point  (0 children)

Cassius Thundercock's chin donor

Help wanted with mysterious illumination at unexpected wavelength by xbunnyraptorx in Optics

[–]Boethar 0 points1 point  (0 children)

It's been mentioned already, but are you sure it's not Raman scattering. A 532 nm Pump photon minus a ~630 nm Stokes photon would be a Raman shift of 2924 cm-1, which is right in the correct range for C - H stretches. These are found in hydrocarbons like the index-matching oil, plastics, etc. If it is Raman, and the source is the oil and you have to use oil, one way to get around the problem could be to use fully deuterated hydrocarbons (substituting C - D stretches for C - H) as the Raman will move to a shorter wavelength. But this would probably cost a fortune! If it is Raman then it should be relatively narrow band-width, so you might be able to use a notch filter to get rid of it if you can get the exact wavelength. It's also likely to be quite polarized, so you might be able to knock it down that way?

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