Name: Sean

Country: Unites States of America
Message: How long can I let a Procion dyed shirt sit without washing it out? We may need to let them sit for a week. Is this alright or will auxiliary chemical reactions happen?

It's not ideal, but it should be okay, as long as you're talking about cotton with soda ash, or silk with an acid such as vinegar. 

If you're dyeing silk with Procion MX dyes and soda ash, then it is very important to rinse it out after no more than a day, because soda ash is damaging to silk.

When you do wash out, start by washing once in cool water, either without detergent or with Synthrapol. This is important for removing auxiliary chemicals. After the initial cool wash, wash at least twice in the hottest water available, with Synthrapol or another detergent, to remove all unreacted dyes.

If you have hard water, be sure to add the water softener sodium hexametaphosphate, as otherwise the dyes may form complexes with the hard water chemicals, making it much harder to wash out all of the unattached excess dye. (See "Dyeing with hard water: water softeners, distilled water, and spring water".)

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