Trying Industrial Chemical Dyes at Home in my Lab

Spray paint it dark green with acrylic paint.

Bake it.

afaik, you can't bleach acrylic without destroying the fiber, so your best bet would be to overdye the yellow with blue to try and get green.

Basic dyes are used for acrylic but you will probably get a bright color not a dark one. You'll want to be sure you have removed any toxic residues before wearing it.

If you really want dark green, you may be better off to knit yourself a hat with some other fiber!

You didn't mention doing an internet search for that hat. You might be able to find it online -- lots of online retailers carry out-of-season stock year-round -- and you could save yourself a lot of trouble.

Hmm... seems to not entirely be the case, just needs some chemicals. According to http://textilelibrary.blogspot.com/2009/03/preparatin-for-dyeing-acrylic-fibres.html you can bleach the acrylic fibers in sodium chlorate / formic acid to prepare them for dyeing.

also, there is http://www.freepatentsonline.com/3891390.html for more reference. It seems the trouble is the solvent, and most people don't have non-aqueous solvents (I do)

I haven't got any NaClO2, but I do have MgClO4, and LiClO4, does anyone have a good reason why that might not work?

It's called "primary research"! Just do what you want, and see if the fumes make you dizzy, high, paranoid, euphoric, silly, etc. Just like in the days Humphry Davy. Please keep alive, and keep us posted!

What about using Chlorox? You can get a bottle at your local market for $1.49

It is very difficult to stip down acrylic dyes from acrylic, especially when dyed with basic dyes.

The only advice is to over dye it with a suitable colour (basic dye ASTRAZON from Bayer or others...) to get to get the final green you want. If the yellow it is dyed with is relatively light, you will be able to overdye it enough to get what you want. You need to TRY !

No bleaching necessary. You can spray paint it, but you need to go to the auto parts store and get the spray paint that is formulated for vinyl car upholstery. It should stick and also remain pliable.

Why don't you buy some material of the color you like and make the hat. Or find a hat of natural material that will take dye. As far as I understand about acrylic materials the dye in put into the material while it's still in liquid form (before extruding) which means it's like dying plastic if you try adding color after the material is hardened. And it is hardened even though it feels soft and pliable. Any dye that you could get to absorb into the material would probably melt the acrylic fibers. That's why it is hard to stain acrylics and it washes out easily. For a yellow had that you want to make green if the dye were able to be absorbed you would use blue. (Blue and yellow make green) There are also many mail order companies online that probably carry the exact hat you had. You might try them. If you get on it you can have your green hat before St. Pattys day.

Plant some grass on it!

_{Sorry couldn't resist.}

Buy a cheap hat and put rodamine dye on the inside hat band at the forehead position. Let the casual thief pick it up and use it. This will mark the thief for about two weeks and make him less likely to steal from you in the future.

http://www.amazon.com/Flourescent-FWT-Red-Concentrate-Pint/dp/B003NUUEKA

This is what you want