using off-white cotton knit, soaked in 3parts vinegar 1 part water, tied with wire around old rusted barbells. There are misc. rusty objects (keys, washers, locks) inside the fabric. I have been spraying it with vinegar/water so it doesn't dry out. I checked a few days ago and the rust dye was fabulous--so I refolded to get more coloration. It is almost ready to unfold again. Am letting it rust for 36-48 hours.