I’m talking about the big classroom size blackboards. Were they actually made of rock slate? How did they cut a huge piece of slate that big without fracturing it using the tools of 100+ years ago?
Traditional classroom chalkboards were made of porcelain surfaces adhered to a metal backing (e.g., steel), not slate. How much a traditional chalk board costs today.
Slate is used for hand held chalk boards.
To answer your other question, a 4 by 5 foot (1.2 by 1.5 m) chalkboard in a wood frame weighs 53 lbs. (24 km).
I had a “slate” in my childhood – a handheld piece of slate framed in hardwood, perhaps 9"x12", suitable for drawing on with chalk. It might have been 1/6" thick, and probably weighed about five pounds, on a guess.
Beg to differ with you. Old schools had real rock slate blackboards all around the rooms. White chalk sticks for writing, felt erasers which had to be ‘dusted’ after school. Earlier than that childern had their own personal slate in a wood frame. Used a hard ‘slate pencil,’ not chalk,l to write on it and a wet sponge or rag to wipe it clean ready to reuse.
Porcelain on steel came later. Didn’t last long. I’m not familiar with what schools use today but businesses are heavily into the dry erase marker type stuff.
We traded off the hazard of chalk dust for the solvents in the dry erase markers!
Yeah - we definitely had slate blackboards.
Remember the competition to be chosen to bang the erasers?
Tangentially related story:
A few months ago I dropped a piece of plywood on its edge on my toes. Busted 3, but was glad they hadn’t been chopped off.
When I was telling my running buddy why I would be out for a couple of weeks, he told me of a friend of his who was salvaging an old school (w/o steeltoes). He was removing a wooden chalk ledge, without realizing that the ledge was supporting the slate. As my buddy tells it, he lost 2 toes. But, as my plywood experience demonstrated, a sheet need not weigh too much to cause damage when dropped a couple of feet onto its edge.
We had slate blackboards in college, which was only 5 years ago! As I was leaving they were starting to redo all those classrooms, putting white boards in (and I assume getting rid of the slate.) I think it’s really sad.
It seems like a lot of people here are assuming that if the surface of a wall-mounted writing board is black & is written on with chalk, then it must be made of slate.
I don’t know that that is true.
Having done grade school through college in the 60s-80s, I encountered lots of black boards & chalk. White boards & dry erase were just a little ways in the future, at least for widespread academic use.
And I doubt any of the boards were made of slate. We had a ~4x6’ blackboard at home. It was beaverboard (ie a very fine-grained particle board made with sawdust, not wood chips) with some black paint-like coating on the front surface.
That surface was indistinguishable from the ones at school.
I know an anecdote is not data, but do here people really know for certain that blackboards in current classrooms, etc., are REALLY made of slate? Or are the just asuming, or maybe using “slate” as a synonym for “blackboard”, rather than a term refering to a type of dark flaky rock?
Well, I know the ones at my alma mater were big hunks of rock, because one of them fell and broke once.
I recall cracked ones in grade school as well.
We had a large painted one at home, and I was very aware of the difference.
Back when I attended the Chicago public schools, many of the blackboards dated from the 20s and 30s if not earlier.
(Starting in 1964 I attended the same grade school my dad attended beginning in 1927. In fact, my elder sister had a teacher who had taught my dad! She retired before I got to 8th grade.)
My suspicion is that a greater percentage of the construction materials used back then were the “authentic article” as they were expected to withstand generations of abuse, and materials and labor were relatively less expensive than today. But I have no cite for that.
Or are you gonna tell me the little holes in our desks weren’t for inkwells? 
I got more than my share, being a goody-two-shoes and all. Primary school I went outside to the brick wall to bang them, but middle school actually had a motorized thingie to slurp the dust into itself.
My father taught us algebra at home to we could skip it in school and we had a small blackboard he used. Before this thread I would have sworn it was slate but perhaps it was chalkboard paint on wood.
Allow me to be the first:
TEACHER’S PET!
Should I admit that my friend Chris and I stayed after school regularly to redecorate the bulletin boards?
begin nostalgia hijack: One of the teachers we helped out was Sister Rosamund and she had a special little box of pins that were half the length of regular ones, and they were what she used to put things on the boards. She had impressed on us just how precious these were and to be very careful to not lose any. Well, one day Chris totally dumped the whole box on the ground. If it had been me, I would have been pooping myself in fear but Chris was fearless and just started laughing (my perfect complement). The mix of pee-yourself giggling and the thrill of the fear of maybe not picking them up before she got back was delicious.
RIP, Chris. Love you, pal. /nostagia hijack
“Slate Paint” is a slate gray paint with a fine grained abrasive added.
A painted surface slate board isn’t worth a flip compared to real rock slate black board. Doesn’t take chalk as well, makes more dust and uses more sticks of chalk!
You can tell the difference just by putting your hand on it. Stone is much cooler, as it conducts heat better. When you washed them with water the water would soak in. Also, in a school like mine that was built in the late 1800s, there were small chips. Sadly, my old elementary school was turned into condos.
There were also el-cheapo chalkboards made out of cardboard, which were for mobile purposes or the earlier-age classrooms.
It’s obvious from many of the posts, how young most Dopers are. As some of us geezers noted, however, black boards “way back then” (30s, 40s) were definitely slate. Stone, that is, really, really, slate!
One time in Vermont I did a story on one slate quarry, and it was fascinating. Mostly Welsh workers from the old country. They were amazing in how they worked the stone. I saw some of them sit before a huge chunk of slate and use a wide chisel and hammer to cut slabs of slate just like slicing bread, perfectly evenly.
These were smaller, so I can’t answer your question about how how those really large slate slabs that we had in schools back then were cut.
A WAG is that they were probably cut with a big band saw. Somebody here should know, eh?
My parochial school had one of those, and only those in 6th grade or older were allowed to use it – younger grades had to bang them together to remove the dust from the erasers (and spread it all over their clothes and everything else!)
Our school’s motorized dust-sucker had a tube on the back side. There was a heavy cloth dust collection bag there, attached with a clamp around that tube. Working carefully, you could use a dime to loosen the setscrew on the clamp just enough so that next time the machine was used, a minute or 2 into use the vibration would loosen the clamp enough that the whole collection bag came off the tube, and it would shoot out a stream of chalk dust like a fire hose, causing a complete white-out of the hallway (and any poor sucker who happened to be walking there at the time).
Or so I was told.
Yeah, we didn’t do mean things like that because we were a parochial school.
Oh, wait.