Acid-free cardboard and paper.

Well-proven gaskets from under 100g. vodka "Stoparik" and the like. Thickness 1mm

what about being a non-drinker?

what about being a non-drinker?

Buy and don't drink

You need white acid-free cardboard with a density of 350g / sq. m and a thickness of 0.5 mm. It is usually imported. It is usually difficult to find such a thin one, it is easier with a thickness of 0.8 mm (~550g / sq. m), it goes to passepartout and some types of archive folders/boxes. You can find it in companies that supply museums and workshops (use the Internet search). But I warn you, if you do not need very many dies, use the standard ones from the store. Because many of these companies do not work with individuals, but only legal entities by bank transfer and under a contract, and the minimum pack of 5 (or 10) sheets of approximately 800x1000-1200mm format, at a price per sheet of 20 rubles.E. (dollars or euros-from the supplier). So one purchase will cost at least 8000r at the current exchange rate. From one such sheet, you can cut about 4-5 thousand medium-sized dies (approx. 20x8). Yes, it is significantly cheaper than the purchased ones in terms of the die (approximately 2.5-3 times), but they need to be purchased, delivered, marked, cut, punctured. And it is better immediately, because it is inconvenient to store such cardboard in the apartment. For the same amount of money, you could buy about 7000 standard dies without any hemorrhoids, precisely and qualitatively made, and even with rounded edges (this is not available without cutting). And I compare it with the price in the store, and there are ways to buy standard dies in bulk. Rather, it is a good option for institutions with large fees, not very strict aesthetic requirements, and insufficient funding.

You need white acid-free cardboard with a density of 350g / sq. m and a thickness of 0.5 mm. It is usually imported. It is usually difficult to find such a thin one, it is easier with a thickness of 0.8 mm (~550g / sq. m), it goes to passepartout and some types of archive folders/boxes. You can find it in companies that supply museums and workshops (use the Internet search). But I warn you, if you do not need very many dies, use the standard ones from the store. Because many of these companies do not work with individuals, but only legal entities by bank transfer and under a contract, and the minimum pack of 5 (or 10) sheets of approximately 800x1000-1200mm format, at a price per sheet of 20 rubles.E. (dollars or euros-from the supplier). So one purchase will cost at least 8000r at the current exchange rate. From one such sheet, you can cut about 4-5 thousand medium-sized dies (approx. 20x8). Yes, it is significantly cheaper than the purchased ones in terms of the die (approximately 2.5-3 times), but they need to be purchased, delivered, marked, cut, punctured. And it is better immediately, because it is inconvenient to store such cardboard in the apartment. For the same amount of money, you could buy about 7000 standard dies without any hemorrhoids, precisely and qualitatively made, and even with rounded edges (this is not available without cutting). And I compare it with the price in the store, and there are ways to buy standard dies in bulk. Rather, it is a good option for institutions with large fees, not very strict aesthetic requirements, and insufficient funding.

thank you for the detailed answer.
When I Googled, I also paid attention to baguette workshops.
they can also sell small wholesale items there?
what about the other characteristics? I have met with carbonate, different % cellulose, with an alkaline reserve and without.
maybe there is some standard for an example? name and manufacturer.