baba-prague
DianeOD said:And that cards were inserted 'as stiffening' - into the spines of books.
Considering that other materials were cheaper, and quicker for this purpose, it looks to me as if the cards were being 'accidentally' protected.
Actually, no. In card production - and I assume this would apply as much then as now as it's never been a simple process - there is quite a lot of wastage. It's because the whole printing and cutting process is more complicated than the printing and binding of a book and so you tend to have a lot of slight mis-prints, poor cuts, damaged cards etc.
To give you some idea of the modern situation (not identical of course, but probably at least indicative) our local card producer, Piatnik, actually uses waste cards as packaging - they have so many.
So logically, it's likely that there would have been card wastage which would be sold off - or given away - cheaply. It would then have provided a source of good quality card stock at a much lower price than clean, new stock. I think it's highly likely that this is why we see it used as stiffening.
One can't of course prove this without finding a receipt or something similar (and, as I say, the waste cards may have been given away in which case there would be little trace of any paperwork) but it seems the most logical conclusion.
By the way, an analogy is the use of slightly off-printed or waste fabric to stuff and weight hems of curtains etc, in the Victorian times (William Morris and Company did this all the time). It looks strange to have beautiful printed fabric used as stuffing in this way, but when you realise it was just wastage that couldn't be used otherwise you can see that it makes financial sense.
_________
Just have to add that it occurs to me that Alex - a great mender of things - has several times used waste cards from our decks as stiffener - even for damaged book bindings once or twice. I do hope that in 450 years no-one discovers this and imagines that we were here saving cards from the great Noughties book burnings. Goodness, now that IS a thought!