Personally, it looks pretty dirty. But it's pretty common in street food anyway

"If you live in Vietnam or learn Vietnamese language, you would have noticed a pretty strange type of beer glass used in many street restaurants - either for iced tea or beer. Vietnamese Language Studies would like to introduce a series of photos depicting the making process of this strange beer glasses- especially in Ha Noi:

The glasses were first made in a village in Nam Truc District, Nam Dinh Province, which is around 100km southeast of Hanoi.
The Xoi Tri Village is currently has three traditional handicraft glass manufacturing factories.
Pham Ngoc Han, a factory owner, said his family has made glasses for over 30 years and his factory is capable of producing around 25 glasses per month.
The main materials for making the glasses are broken glass pieces which can be bought at a very cheap price of VND 20,000 (US$0.89) per 10kg.
“This kind of glass has become a symbol of the Hanoi lager,” Han said. “The beer selling shops have chosen the glasses and placed orders for them for years.”

The owner said he and his employees take turns in their shifts to work 12 hours per day and the profit they earn can just cover their daily necessities.
Han said as China’s crystal products have flooded the Vietnamese market, his factory only has chances to produce this kind of glass when Chinese people do not want to make it due to low profits.
“And then it becomes what we can lean on to live,” he added.

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