Archive for March 9th, 2020

Diamond-Drag Styrene Engraving: Scraped Sharpie

Applying only two Sharpie colors to the third quadrant of the engraving testpiece produces a more restrained result:

Diamond on styrene C - scraped red-black Sharpie - start
Diamond on styrene C – scraped red-black Sharpie – start

Instead of sanding the surface, I used a paint scraper to remove everything down to the engraved grooves. The scraper in the upper right is a Rubbermaid 54807, which is apparently no longer available. If I ever buy a new scraper, I’ll spring for a carbide blade.

A dirt speck under the plastic sheet can still obliterate the markings, though:

Diamond on styrene C - scraped red-black Sharpie - first clearing
Diamond on styrene C – scraped red-black Sharpie – first clearing

Overall, the results look just like a real slipstick:

Diamond on styrene C - scraped red-black Sharpie - 225 300 g scale detail
Diamond on styrene C – scraped red-black Sharpie – 225 300 g scale detail

The upper scale was engraved at 225 g downforce, the lower at 300 g, with corresponding differences in width & depth.

Seen at higher magnification with omnidirectional light through the microscope, the tick marks have more detail:

Diamond on styrene C - scraped red-black Sharpie - 225 300 g line detail
Diamond on styrene C – scraped red-black Sharpie – 225 300 g line detail

The upper ticks are 0.1 mm wide and the lower ticks a scant 0.2 mm wide. Both ticks on the sanded Sharpie sample were close to 0.1 mm, which suggests:

  • Scraping removes less plastic
  • The grooves have a flat-ish bottom and side walls roughly matching the slightly worn 60° diamond tool

Sharpie ink is, of course, soluble in alcohol:

Diamond on styrene C - scraped red-black Sharpie - alcohol wipe
Diamond on styrene C – scraped red-black Sharpie – alcohol wipe

That’s not unexpected, as I’ve been removing Sharpie with alcohol forever, but it’s worth keeping in mind. I don’t know if spraying a clear topcoat (Krylon FTW!) would provide good sealing with enough wear resistance.

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