Here are the instructions you'll find online. I posted these on another site recently.
If you want to use fabric store muslin to do yourself, buy the 108". Buy some RIT dye, and have a plastic bucket to use, some household rubber gloves, boil about 3-4 gallons of water on the stove top. Wash the fabric first, then while it's wet, don't dry it, lay it out on your floor, and crumple it randomly and bunch it up, and then tie the whole ball of fabric up with twine or jute, tightly.
Either outside, or in your kitchen sink, CAREFULLY add your dye to the hot water, in your bucket with 1 cup of table salt and stir it in, and add the fabric. Wear your gloves at this point. Make sure your fabric is completely submerged in the water for a full 1/2 hour. Don't stir it, just let it sit, making sure it's covered.
Now you have to rinse it. Don't splash the water if you can help it, as it will stain everything permanently! Rinse, rinse, rinse until all of the water runs clear. This will take a little while, then you can spin it out in your washer, and dry it on low heat in the dryer. I usually do a rinse and spin in the washer, to get as much of the dye out as possible.
There's a ton of info on the net for making backdrops.
Hope this helps, if ou have any questions, just PM me, and I'll try to help som more. Also this will give you a tie dye look
This is my gallery , and the first six pics are with homemade backdrops.
Jess

equipment: Nikon D300 and D70, Tamron 28-75mm 2.8, Sigma 50-150mm II lens, 18-70mm, 50mm 1.8, and 70-300mm, PSE 6, SB 800
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