Sharoper Sharoper
I want to overdye a silk jacket using Procion MX because I don’t want to use hot water.  Somewhere I read that I need to acidize the dye bath.  So, do I use vinegar instead of salt and soda ash.  One place I read to put salt in right after dye before fabric and another place I read to put salt and soda ash in toward end of process.  Is the pH of dye bath most important for fixing?  And what should it be for this situation?
    Thank you in advance.
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Jacquardmod Jacquardmod
Hi,

I am running a test on this today.  The basic idea is, yes you need to acidify the bath before dyeing instead of using soda ash.  I would use 1/4 cup of citric acid per gallon or 1 cup of white vinegar per gallon.  

You should do it just like you would the bath if it had soda ash, just with this change. 

So

Dye in the water first

Add wet fabric

Add acid and stir stir stir

Final addition is 3 cups of salt at 5 min intervals  between cups with lots of stirring.  
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Sharoper Sharoper
Thank you.  That makes sense.
Let me know how the test turns out.
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Jacquardmod Jacquardmod
https://www.jacquardproducts.com/forum?p=post%2Fcomparison-of-batch-dyeing-protein-fiber-with-both-procion-and-acid-dyes-10615572%3Fpid%3D1312330281

So I ended up writing this up.  I think maybe acid dye will still work better for you.  The thing is for the acid dye, you should use a pure color.  Mixtures like browns and greys or deeper colors like vermillion may not turn out like they would on the bottle.  

I think the test surprisingly showed the acid dyes can work well at low temp. I would do a longer dye bath.  1.5 hrs maybe if you want a dark color with a pure color.  
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