Reactive Dye Fixative

[nemi]

Do you use Reactive Dye Fixative when doing low-water immersion dying with Procion MX Dyes?  I just recieved a large shipment of colors (20 colors  ) and chemicals, and I ordered the Fixative as well.  But I can´t remember having read anything about it, and it is not mentioned in the book I have bought (Color by Accident) 
Should I use it?  Is it necessary?  Will it help the colors being more washfast?  (I´m coloring silk)

[pburch]

"Reactive Dye Fixative" - sounds like a brand name. Where did you get it? Is it a liquid or a powder? Does it come with any instructions? These would provide a major clue as to its identity.

If it's a powder, it's probably soda ash, also known as sodium carbonate, or Na2CO3. If you are not steaming your silk, you must use soda ash or another pH increaser to fix your dyes to the fiber. If you are steaming after you apply the dye, you can substitute vinegar, to use the acid method, but only because you're dyeing silk; never try the acid method with cotton or rayon. Soda ash is what is called for in the recipes in the book Color By Accident. The easiest and cheapest way to acquire it locally is at any place that sells swimming pool supplies. Do not confuse it with sodium bicarbonate, or baking soda, whose chemical formula is NaHCO3; sodium bicarbonate does not raise the pH high enough.

If it is a liquid, then it's most likely sodium silicate, or Na2SiO3. You can use it instead of soda ash. The usual instructions for this liquid are to paint with dye (dissolved in water) on fabric, let it dry, then paint on sodium silicate as an after-fix. There is no need to use it if you also use soda ash, and it should not be used with vinegar (since they will cancel each other out, and also because the acid of vinegar can turn sodium silicate to a difficult-to-remove gel). Both soda ash and sodium silicate serve to increase the pH of the dye reaction. All of the recipes at the Tobasign web site call for this liquid, which they sell as Toba-Fix. I am not sure how much sodium silicate liquid you should use for LWI, if you are substituting it for soda ash. Ideally, when dyeing with Procion MX-type dyes, you should use the amount that, when mixed with the same amount of water as the total you use to add your dyes, yields a pH between 10.5 and 11.

Hre's a link to my FAQ page on soda ash and its substitutes:
What is soda ash, and what's it for in dyeing?

There is also a small possibility that it's a cationic dye fixative, like Retayne or Dharma Dye Fixative, but that's less likely since the cationic dye fixatives are not necessary for properly fixed and washed-out reactive dyes. They are useful for making all-purpose dyes and direct dyes less prone to run in the laundry, and are sometimes used by people who have not learned how to wash excess dye out after dyeing with reactive dyes. You can recognize it by the application instructions, which are to add a small amount to hot water and agitate for something like twenty minutes, or to add in a load of laundry.

Paula

[nemi]

Thank you Paula - you really know your way around the chemicals!  I get a little dizzy just trying to remember the different names 

It´s a liquid from Jacquard Products.  It´s not soda ash, I guess, since they sell that as well and mark it "soda ash".

Description in catalogue:  "Used to fix reactive dyes to increase washability and to increase color yield on the fabric".

Instructions are to use it after the dyed fabric has been rinsed with Syntraphol.  (1/3 oz. of Fixative per pound of fabric, soaking for 20 minutes)

I´m also using soda ash, so from your answer I guess that I won´t need to use this?

[pburch]

Right, you won't need it.

It can't be sodium silicate, because you have to use sodium silicate with the dye on the fabric, just like soda ash, not after rinsing the fabric. Those instructions appear to imply that it is a cationic dye fixative like Retayne, but there is absolutely no need for such a product if you know how to use fiber reactive dyes.

After you finish batch-curing your dye with your soda ash, allowing your dye plenty of time to react with the fabric in a warm enough place (21°C or higher), you should wash the fabric thoroughly to remove all unattached, unreacted dye. I like to wash once in cool water, to remove all soda ash and other auxiliary chemicals, then twice in very hot water, 60°C or higher, with Synthrapol or another detergent. The hot water will remove all of the unattached excess dye. Hotter water works better than cooler water.

Using a cationic dye fixative instead of proper washing out of dye is not a good idea. The fixatives actually reduce the lightfastness of many dyes; that means, the dyes may fade more quickly in the light. One of the things we love about Procion MX dyes and other fiber reactive dyes is that, with the temporary aid of soda ash or another source of a high pH, they actually form a permanent chemical bond to the fiber itself. That's the way that they work. There is no need to glue the fiber in with an additional fixative chemical, since you are using a high quality dye.

You will probably find a use for this product, though, even though you do not need it when you dye your own fabric. Cationic dye fixatives are a wonderful thing to have on hand when a commercially-dyed garment turns out to run in the laundry. The fixative molecules stick to the dye molecules, making them larger and less soluble in water. This is important when an inferior dye is used. The loss in lightfastness is a small price to pay for not having a bad dye job bleed all over your laundry.

Paula

[nemi]

Thank you so much for your help, Paula!  That´s very useful info.  Good thing I did not buy too much of the stuff, I guess I can always use it for commercially-dyed garments like you suggest.  I definately do not want to reduce the lightfastness of my silks, so it´s good that I asked! 

Without this forum I think I would spend at least twice as long learning how to dye!