community of dyers

Hi Paula - All this chemical talk inspired me to look on the bottle of laundry bleach that I buy at the supermarket to see what is in it - it says active ingredient: Sodium Hypochlorite 52.5g/L. Is this the same as Sodium Chlorite? Anyway, this bleach works well - although you have to soak the garment in it for a couple of hours to get it the lightest shade possible. Oh, and then further down the bottle it says 'AT USE BY DATE: available Chlorine 2.0%m/v. Sodium Hydroxide 10g/L' - what does this mean?

It looks like what you have there is standard, ordinary chlorine bleach, which is normally 5% to 6% sodium hypochlorite, often with sodium hydroxide as well to keep the pH up. It is not the same thing as sodium chlorite.

This stuff works well on removing stains from white clothing, and is great for cleaning as well as for discharge dyeing. It is also toxic, so avoid getting it on your skin or spending a lot of time using it without good ventilation. If you have extensive careless exposure, it can make you seriously ill. (See Why we should be very careful when using chlorine bleach, from the Oct. 19 2005 entry in my All About Hand Dyeing weblog.)

The big warnings about hypochlorite bleach are:
   - never mix it with ammonia-containing cleansers, and
   - never mix it with any acid
Mixing hypochlorite bleach (NaOCl) with ammonia (NH₃) produces deadly and/or explosive chemicals such as chlorine gas (Cl₂), nitrogen trichloride (NCl₃), and hydrazine (N₂H₄). Mixing hypochlorite bleach with an acid, such as vinegar, also produces deadly chlorine gas.

This kind of chlorine bleach is the one that we're always talking about needing to use Anti-Chlor or Bleach Stop or hydrogen peroxide to neutralize afterwards, as otherwise the fabric continues to be degraded in spite of washing.

Yea, I wanted to find a better alternative to using bleach since its kinda bad and it can damage fibers like crazy. I mentioned thiox but everyone at the chem shop gave me a blank stare. It doesnt look like anyone has thiox anywhere in Taiwan. But then if they do make it here you probably need connections and buy lots of them or something. Weird thing about trying to get certain chemicals, if its not commonly used (like hobbyist) then getting them is next to impossible.

Did you use the brand name 'Thiox', or did you use the chemical name, thiourea dioxide? You know that they are never going to understand our US suppliers' brand names in other countries, but they might have the chemical. It is also called formamidine sulfinic acid; try that. The chemical formula is CH₄N₂O₂S. China produces a huge amount of this stuff for industrial use, as you can see if you try a quick Google search with 'thiourea dioxide'.

As Jaja said, Rit Color Remover and similar products contain a reducing discharge agent which works a lot like Thiox. Its chemical name is sodium hydrosulfite, and it is generally sold mixed with sodium carbonate for dye removal in the washing machine or on the stovetop.

true, however I did give them the name "thiourea dioxide" and I got blank stares too. I guess its true that they make lots of them in China but it is probably uncommon in hobby or home use therefore very hard to find unless you have "connections" (people in Taiwan keeps those thing like trade secrets, its impossible to know who supplies what unless you like work for them for a long time) however "anti chlor" or bleach neutralizer is there, but its sodium thiosulphite... but I found this thing called "sodium hydrosulphite" I dont know if its same as "anti chlor". They called it "safety powder" or something...

so far my last trip to the chem shop left me extremly frustrated and empty handed... all I saw (of interest) was technical grade Potassium Permaginate and aluminum powder, 325 mesh, conc. sulphiric AND HF acid (something I DONT want in my house), conc. HCl, 35% H2O2 (I presume for hair bleaching), misc. organic chem's like Benzene, some Reagent ACS Potassium Nitrate (which is too expensive), iron oxide.... perhaps if I am in the mood for some pyromaniac fun then I might look at them...

but I found this thing called "sodium hydrosulphite" [...] They called it "safety powder" or something...

Yes, that's what you want for discharging! It's the same thing as Rit Color Remover. I'll look for a recipe for you.

First, don't buy a large container of this stuff. Small packages are fine. There's a danger of spontaneous combustion if it becomes damp, i.e. burning your house down. The little boxes of Rit Color Remover contain 2 ounces of a mixture of an unknown ratio of sodium hydrosulfite and sodium carbonate.

If you substitute sodium hydrosulfite for thiox, use five times as much, by weight. It works fine for me to use two to three boxes of Rit Color Remover in the washing machine (depending on how full I fill it) at our local maximum water temperature of 140°F (60°C), but it should be more effective at higher temperatures; it is often used on the stovetop. The fumes while you are cooking it with the fabric can be bad.

In Kate Broughton's book, Textile Dyeing: The Step-By-Step Guide and Showcase, Carter Smith's instructions say to mix up two gallons of sodium hydrosulfite solution 'according to directions' (presumably the package instructions, since none are included in the book). The tied silk to be discharged is placed in a bucket of cold water to soak for five or ten minutes, so that "the water will act as a resist later when you place the silk in the discharge bath". Obviously you will omit the presoaking step for solid-color discharging. Next it says,

Carefully place the wet silk in the discharge bath that is simmering on the stovetop. (The discharge bath can be held in a pan or pot; ideally the container should be big enough to hold the wrapped silk without causing it to buckle. Smith found his tubs at a restaurant supply house.) Take care not to splash the solution, and be sure you are working with plenty of ventilation. The discharge process produces unpleasant and unhealthy fumes.

I can't tell you exactly how much sodium hydrosulfite to use since my recipe is for Rit Color Remover, which contains sodium hydrosulfite, sodium carbonate (soda ash), sodium metasilicate (prevents clumping), and EDTA (helps keep metal ion contaminants quiet). The total weight of the mixture is 56.7 grams; this quantity is only one-half of the amount required for a twenty-gallon washing machine load containing about five pounds of clothing. Here is the Rit Color Remover recipe:

Stove-top method. Wash items as usual. Do not dry. Fill large stainless steel or porcelain enamel pot (not aluminum or non-stick) with water, allowing room for items. Heat water to simmer [190°F or 87°C]. Carefully add Color Remover, pouring just above water level. (AVOID BREATHIG DUST. USE WITH ADEQUATE VENTILATION.) Stir to dissolve thoroughly. Carefully add wet items (avoid crowding); stir continuously with a long-handled spoon or stick, 10 to 30 minutes so color will be evenly removed. DO NOT BOIL. Carefully drain solution into sink. Using rubber gloves, thoroughly rinse items, first in hot water, then in warm water (RINSING IMMEDIATELY IN COLD WATER MAY SET CREASES). Squeeze gently to remove excess water. Rewash items with detergent.

The thiourea dioxide recipe may be a useful guide to the amount of sodium hydrosulfite to use, since you should use five times as much sodium hydrosulfite as thiourea dioxide. PRO Chemical & Dye's instructions for thiourea dioxide discharging say to mix 10 grams of Thiox with 10 grams of soda ash in 2.5 gallons (10 liters) of water. I guess that means you might use 50 grams of sodium hydrosulfite plus 10 grams of soda ash in 10 liters of water, in order to follow the Rit Color Remover Recipe with your pure sodium hydrosulfite.

Incidentally, sodium hydrosulfite is generally said to be about 90% pure, so if that's what you see on the label, you've got the usual concentration.

I think that if I would search for thiox here, my experience would be the same as yours - BUT - if I check products that are sold by companies producing local branch of RIT dyes, they do have dye remover, that is in fact nothing else but thiox.
Have you checked this out?