[JasonCEC]

Edo-kiriko is one of 2 great glass traditions from Japan; the glass is thick, feels similar to Murano glass, with the edges of the cut pattern "sharp".[0]

There is also a tradition of thin glass (without etching), where the glass is blown to be paper thin and you can feel it flex as you hold it. This is called Usuhari - "Usu" means thin and "Hari" means glass[1]. Shotoku is the best maker, creating a variety of specialty drinking glasses of many shapes.

I have a small collection of Japanese drinking glasses at home which I use regularly and freely use with friends[2] - everyone loves drinking beer or sake from the Usuhari glasses. Shotoku actually did a collaboration with one of the Edo-kiriko makers, by blowing a small sake cup with a thick Usuhari glass ~ it's amazing, and I use it as my personal spirits cup.

[0] Not sharp enough to hurt, yet very noticeably present.

[1] usuhari glasses are exceptionally thin at 0.9mm. Paper is ~0.1mm, so I'm slightly exaggerating.

[2] less expensive than the Edo-kiriko.

[joshu]

I would worry about the usuhari glass breaking, no?

[kurthr]

I don't know the process they use, but it would not be unreasonable to harden such thin blown glass with a "pickling" process. This would make it much harder (to resist scratching), tougher (more difficult to crack), and more safe (breaking into many pieces rather than a few jagged ones). The process replaces smaller (typically Na) with larger (typically K) ions putting the outside of the glass in compression.

Notably, cell phone glass (eg Gorilla) is similarly hardened and can go down to 0.7-0.4mm while maintaining these properties.

[JasonCEC]

Shockingly strong! I've always wanted to see the glass blowing process at their factory in Tokyo, but they've been closed for tours while upgrading for at least ~2 years before covid (when I was frequently in Japan).

My understanding is that they use some type of cold annealing process that strengthens the thin glass.

I've not managed to break one in 4 years of dinner party use.