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xkcd #3194: 16 Part Epoxy
(thelemmy.club)
Title text:
Some surfaces may seem difficult to glue. But if you research the materials, find tables of what adhesives work on them, and prepare your surfaces carefully, you can fail to glue them in a fun NEW way that fills your house with dangerous vapors.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3194/
So magnetic tape (tape cassettes, VHS/Betamax, 8 tracks, etc) is powdered iron (II) oxide and works by being magnetized to write data to it. So yeah. Quick search revealed it's totally a thing and you can buy it, primarily in industrial quantities.
As for a magnetic table, you don't even need it powdered, hell you could probably just get two stainless steel sheets, four stainless steel strips, a matrix with holes in the proper positions, and a bunch of high powered small permanent magnets and make your own magnetic table without it being that difficult to make