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[Fullflame333]

I'm currently trying to darken a 100% polyester vest, and some felt for a cosplay that I'm working on. I need to darken both fabrics to different shades of grey, and I tested using a regular fabric dye on them and it really didn't do much.

I've been looking around, and I do see the tutorials for dying wigs with sharpies, does this apply for things like larger vests and about a yard of felt fabric? I'm a little bit lost.

And on the sharpie method note, I did read somewhere that sense sharpie black isn't exactly black but dark shades of other colors, what should I use to darken my fabric?

I'm making a cosplay based off of the companion cube from portal, if anyone wants a general reference for the colors I'm going for. The vest I have is already grey, but I want it to be darker grey.

[Sarcasm-hime]

There is a dye made specifically for polyester, as normal fabric dyes won't work. It's called Poly I-dye.

[Yui]

I-Dye Poly is awesome. *_* Also, it is very accessible. I have gotten it from Jo-Anns and Blick, and I think you can find it at Micheal's too.
Here's the spec page for it = http://www.jacquardproducts.com/products/dyes/idye/

[Kama]

Dyeing polyester, in my limited experience, is absolutely thankless. You are braver than I am to attempt it. It is entirely possible, but keep in mind you can not dye polyester like you would cotton.

I-Dye poly does get the job done. However I've found it isn't very good for really dark, rich colors. I was trying to dye a light gray base to black and it ended up some really weird bluish grayish color. I wouldn't use sharpies, for the smell and the fact they have to be dissolved into alcohol which can damage/discolor fabric. In the case of felt I Would think it would make it kind of...sticky too.

You must use the stove-top dyeing method for polyester. You can read about it here and see what you are getting yourself into. Make sure you have a pot big enough for the vest, and one big enough for the fabric. It's pretty straight forward once you get started but I had a horrible time finding containers big enough to dye in.