I poured out my leftover coffee to the other side of my vinyl patch (don't want to bag to be outside-shiny, so I ironed it on the inside. Think of it like a laminated fabric or good sub for oilcloth. Feels like a fabric being double-interfaced).
Flipped it up and notice that I had forgotten about the interfaced part. So I poured some on that part. See top right coffee patch.
Flipped up again! And voila! You can see that coffee seeped through fabric and interfaced fabric but not the part where the vinyl is..see the square trace on the tissue paper.
Iron-on vinyl are available in 17" width and sold by meter. Email for inquiry.