When the pen is used, people can clearly see the residual ink in the pen from the transparent ink bag, which is convenient for people to supplement ink at the right time.

使用时，透明的墨水囊可以让人们随时清 楚地了解笔内剩余的墨水量，便于人们在合适的时间补充墨水；

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Coe had to draw dozens of chemical structures in indelible ink to make transparent slides.

FORBES: Magazine Article

For example, iron-gall ink, commonly used on ancient documents, is transparent to infra-red light and most visible in the ultraviolet region of the spectrum.

ECONOMIST: Monitor