Nice to see the modern options available, Tony.
Might also be worth seeing if you could get samples from any supplier of the 100% cotton items in as heavy a weight as possible. I think the original wartime stuff was in the order of 18 to 16 oz. I don't think they worried about thread count for that stuff.
Different mills probably have different production capabilities. Some can probably waterproof and mould protect on site, but most may not. Any dyed canvas is going to bleed like a stuck pig if it is not waterproofed, so the fact it might bleed just means the cloth has not been treated in any way. That probably opens up canvas products to a larger potential market for sales. If the buyer happens to be a tent maker, they may purchase bulk canvas in any colour and waterproof etc themselves, have it done by the canvas manufacturer or outsource that part of the work to a 3rd party company.
It might be cost effective to get a 100% cotton heavy weight canvas untreated in the colour you want and then apply suitable coatings yourself.
Also, I wouldn't worry about shrinkage too much. All canvas shrinks when wet, Even the treated stuff. It's the nature of the beast. My M38 top was a Beachwood Canvas product out of the USA. It was a nice relaxed fit in the summer heat and would snug up a bit in colder Fall/Winter weather. But get it wet in the Summer and it would tighten up so much a group of Taiko Drummers could have performed a concert on it! Same thing used to happen with my M37 top come to think of it, though not so much the end curtains for some reason.
You could always stitch up a one foot square of whatever you end up working with, soak it, toss it in the sun to dry and see what sort of shrinkage you get before and after waterproofing. That would give you a good idea of the wiggle room you would need to factor in for the actual parts making.
Keep up the great research!
David
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