The context is an article about Sir Christopher Zeeman, the mathematician who founded the Maths Institute at the University of Warwick (UK) back in the 50s or 60s. Talking about how they tried to emphasise the social side of things at this new Institute, the article reads:

"Morning coffee and afternoon tea were served from elegant china in a comfortable common room where staff, graduates and visitors gathered for mathematical conversations. Greenglasses were available around the walls so that diagrams could be drawn at the drop of a saucer."

What are these greenglasses? I can't find the term in any of my dictionaries, and I'm curious to know.

I've never heard of greenglasses. Maybe a glass version of a blackboard so you could see the diagram from both sides. Beats me why you'd want to see a math diagram from both sides though, I can't understand them from the front.

I found this in an (other?) article on the history of mathematics at Warwick:

... we changed all the blackboards for greenglasses, which were made of glass with a rough surface on the front to take the chalk and green paint on the back that does not wear off.

http://www.maths.warwick.ac.uk/general/institute/histories-small.pdf

Yes, that's a different article, Sparteye, but at least it's got an explanation of the greenglasses in it! Thanks a lot. I'm pretty sure I've never seen this type of blackboard, though.

The blackboards of the old school were absent from the Purlieu Street School. In their place were devices much like them—extensive flat things mounted on the walls, meant for writing—but these were green. What were we supposed to call them? Greenboards? Green blackboards? Why had this change come about? The official explanation was that yellow chalk on a green board would be easier on our eyes. To Raskol, that seemed unlikely. “They’re trying to confuse us,” he said, and he sighed and shook his head slowly, as if his suspicions about the true purpose of school had finally been confirmed by these green blackboards. (Years would pass before chalkboard [E.A.] became the general term, and during the intervening period of uncertainty the nation’s youth, innocent victims of a summertime revolution in the technology of wall-mounted writing surfaces, sat puzzled through millions of student hours pretending to listen to geography and geometry but unable to stop asking themselves, “What the heck should I call that thing on the wall?” [from Where Do You Stop, by Eric Kraft]

My elementary school(Our Lady of Mercy--Marion Avenue, Bronx NY) had greenboards-

i didn't know/think they were made from glass, but we did call them 'blackboards'--tho, occationally, 'chalkboards'was used(or did i learn that word later?)

2 of the 4 classroom walls were covered with them.

often, with the overcrouded classes, students had seats next to a chalkboard, and would write small notes on them.
teachers had freedom to make the wall at right angles to the windows, or opposite the windows 'the front' of the class. (opposite was often chosen on north facing classrooms)

i remember being surprized in HS, that classes there had fewer students, and blackboards only on one wall.

I think them greenboard/chalkboards are different than the greenglasses things.

maybe not..

The school also featured, according to news accounts of the day, such modern innovations as a public address system linking the principal's office to all rooms of the school and green glass chalkboards, replacing the old familiar blackboards. The new building was dedicated on May 14, 1950.

well, I've had greenboards in my classrooms, and they weren't made of glass. I'm only saying...
you can even buy green chalkboard paint. we had a neat chalk table.

From a commercial site:
Writing surfaces in green glass, green steel and white steel
The glass writing surfaces ensure particularly easy chalking/erasing while the steel surface has the additional facility to accept magnetic aids. Drymarker pens are used on the white surfaces.
Intriguing question, Marianna! I never know what I'm going to learn here.

re:you can even buy green chalkboard paint.

And black chalkboard paint too--my daughter is planning on "painting" a large chalk board in her kitchen (and adding a narrow shelf for chalk and erasers, too)

OLM (my elementary school) also had 'modern' conveniences like a PA system. by 1962 or so, every class has a TV too, and we were notified over the PA that day in November '63 to turn it on..(for me, it was Music class..Miss Lang)

> I never know what I'm going to learn here.

Yep. It's a significant feature of The Learning Experience. :]

Ya but drymarker's on white surfaces tend to mark permanently if the notes are left on the board for a relatively short period of time. And, if your hand brushes agains the writing, it stains your skin. A bit annoying.

I find it much messier than a green or black board.

Newsprint and squeaky pens seem to be ordained for church meetings by the following passage from Leviticus:

"When thou takest counsel one with the other over whither thou shall go and what thou shall do, thou shalt write upon the page of a large book, two cubits wide and three cubits tall, standing on a stand in the midst of the company, and make a fragrant offering of the ink with which thou writest upon the pages of the book. Every one shall see what is written there and know that I am the LORD thy God."

There you go...interpreting again...I see no mention of squeaky pens there.

One good think about greenboards/chalkboards is that Teacher cannot draw his/her nails down the board to get the attention of the class!
Makes me shudder just thinking about that noise!