When I measure fabric I use a caliper rather than a micrometer. I squeeze the jaws with both hands to get my measurements. There is "pillow ticking" and there is also "mattress ticking". Mattress ticking is a bit thicker and, IMO, makes better patches. The "pillow" is about .015" or a little less; "mattress" is about .016" or sometimes + or -. While I still use them from time to time, I mostly use either cottton duck (.019") or my favorite heavy, unbleached canvas (.024"). Snugged in the caliper jaws the canvas measures about .030"; but compressed I get around the .024" mentioned above. For me, the canvas actually seats more easily than the duck. Denim is popular and I have used it at times. But I've consistently had it seat rather grudgingly.
Young guys should hang out with old guys; old guys know stuff.
Really, that thick? I've been wearing Carhartt made in usa double layer knee pants to work for years. They certainly aren't short on toughness, as I have some that were worn weekly for 5 years or more, and the outside knees are just starting to wear thin. I've got a couple well used pairs that I've been using for canvas patch material. I never thought to use it in the muzzleloader, as it is at least twice as thick as pillow ticking.
What size ball are you using with those thick patches, and what gun?
BP | Bronze Point | IMR | Improved Military Rifle | PTD | Pointed |
BR | Bench Rest | M | Magnum | RN | Round Nose |
BT | Boat Tail | PL | Power-Lokt | SP | Soft Point |
C | Compressed Charge | PR | Primer | SPCL | Soft Point "Core-Lokt" |
HP | Hollow Point | PSPCL | Pointed Soft Point "Core Lokt" | C.O.L. | Cartridge Overall Length |
PSP | Pointed Soft Point | Spz | Spitzer Point | SBT | Spitzer Boat Tail |
LRN | Lead Round Nose | LWC | Lead Wad Cutter | LSWC | Lead Semi Wad Cutter |
GC | Gas Check |