Web www.pburch.net
Paula Burch's All About Hand Dyeing
Overview Fiber Reactive Dyes Direct Dyes All-Purpose Dyes Acid Dyes      Food Coloring      Lanaset Dye      Acid Levelling (Kiton) Natural Dyes Vat Dyes Disperse Dyes Basic Dyes Naphthol Dyes Fabric Paints
Index How to Dye with
    Fiber Reactive Dye
How to Tie Dye How to Batik Low Water
    Immersion
Dip Dyeing Washing Machine
    Dyeing
How to Tie Dye
    with Kool-Aid®
How to Tie Dye with
     All Purpose Dye
How to Dye and
    Paint Fabric
    with Light
cellulose fibers:     cotton     rayon and
     bamboo
protein fibers:     silk     wool synthetic fibers:     acrylic     nylon     polyester     spandex other materials...
acetic acid alginate ammonium sulfate baking soda citric acid ludigol mordants salt soda ash sodium silicate temperature synthrapol urea vinegar water softener
Index Batik Mandalas &
    Peace Signs
LWI dyeing Watercolor Rainbow
    Drip-dyes
Tie Dyeing Spray Dyeing Fabric Paints and Markers
The Dye Forum Book Reviews Find A Custom Dyer Old Q&A Blog Blog of Questions
     & Answers (new)
Search Contact me Link here About This Site
Where to Buy
    Dye & Supplies
Mailing Lists Other Galleries Other Informative
    Sites
Additional Links
Index General Dye
    Questions
Fixing Dye Synthetic Fibers Color Choice Dye Auxiliaries Bleaching and
    Discharging
Safety Procion Dyes Acid Dyes Problems Tying Miscellaneous
Facebook: All About
    Hand Dyeing
Twitter @HandDyeing Google+
Procion MX Dyes Jacquard Acid Dyes Other Dyeing
    Supplies
Fabric Paints, Dyes,
    Books, and DVDs

You are here: Home > All About Hand Dyeing > FAQ > discharge dyeing > neutralizing bleach

Advertisements

ordinary household bleach Clorox Ultra Bleach


bleach in a pen
Clorox
Bleach Pen


3% hydrogen peroxide Hydrogen Peroxide 3% can be used to neutralize after bleaching



Sodium Bisulfite is also sold for use in photography and food preparation

Excalibur Sodium Bisulfite

Use food-safe grade sodium bisulfite as an antioxidant to preserve the beautiful natural colors of your fruits and vegetables and prevent the browning that can occur when dehydrating.

How can I neutralize the damaging effects of chlorine bleach?

Experienced dyers agree that the effects of unneutralized chlorine bleach discharge are deadly to fabric. Some residue of the hypochlorite remains in the fabric even after washing, later resulting in holes or thin spots wherever bleach was applied. Fabric that looks fine after bleaching may be in rags a few weeks later.

The answer is to neutralize your fabric after you bleach it.

You must also strictly avoid using chlorine bleach on any synthetic fiber, such as polyester, nylon, or spandex, because the damage done by chlorine bleach to synthetic fibers is irreversible. Use only 100% cellulose fibers, such as cotton or hemp, for bleach discharge. (Some synthetic fibers such as nylon can be safely discharged with another chemical, instead of chlorine bleach, known as sodium hydrosulfite or sodium dithionite.)

What NOT to use

Whatever you do, never use vinegar or any other acid in an attempt to neutralize your chlorine bleach. It will destroy the hypochlorite that is the active ingredient of chlorine bleach, but only by turning it into much more caustic and dangerous chemicals, including hypochlorous acid, which is very damaging to textiles, and, if the pH gets low enough, deadly chlorine gas. Unlike stronger acids, vinegar is unlikely to produce a pH low enough to generate much chlorine gas, but hypochlorous acid is even more damaging than hypochlorite.

It is very disturbing that a number of dyeing books with otherwise good information blithely pass on this dangerous advice, to use vinegar to neutralize chlorine bleach. I worry that a book with such bad information may include other dangerous misstatements.

Good neutralizers for chlorine

There are three good alternatives for neutralizing hypochlorite bleach: bisulfite or metabisulfite, thiosulfite, or peroxide.

Bisulfite and metabisulfite

Bisulfite, or metabisulfite, is the most economical choice. It is widely sold under the name Anti-Chlor by dye suppliers. It does not matter whether you buy sodium bisulfite or potassium bisulfite. It is economical because only small amounts are required. If your dye supplier sells anti-chlor, be sure to order some the next time you order dyes.

Bisulfite is also used as a preservative of fresh and dried foods, such as the potato salad in restaurant salad bars, or dried apricots. A good local source would be your local home wine brewing supply store, as sodium bisulfite is widely used for sanitizing the fruit juices to be used in wine, to stop yeast growth, and as a preservative. Camden Tablets are a product sometimes used in wine-making; each tablet contains 1/16th teaspoon (0.3 ml) of sodium bisulfite.

Here is the chemical equation describing the neutralization reaction between sodium hypochlorite and sodium metabisulfite:

Na2S2O5 + 2NaOCl + H2O —> 2NaHSO4 + 2NaCl

An alternative reaction is as follows:

Na2S2O5 + 2NaOCl + H2O —> 2Na2SO4 + 2HCl

(Source: R.J. Xie et al. Desalination and Water Treatment vol. 3 (2009): pp 193–203 [PDF].)

Thiosulfate

Sodium thiosulfate, also known as Bleach Stop, is another excellent choice for neutralizing chlorine bleach. It is less economical than Anti-chlor because you must use a much larger quantity to prepare your bleach neutralizing bath. Thiosulfate is commonly used in developing photographs, so you may be able to find a local supplier in the form of a photography supply store. The reaction between thiosulfate and hypochlorite is as follows:
4 NaClO + Na2S2O3 + 2 NaOH → 4 NaCl + 2 Na2SO4 + H2O

Peroxide

Hydrogen peroxide is a third choice, perhaps preferable for asthmatics who are sensitive to the effects of sulfur-containing chemicals. It is more expensive than Anti-chlor or Bleach Stop, but it has the advantage of being readily available at pharmacies. Look for 3% hydrogen peroxide among the first aid supplies at your local drug store. The chemical reaction between hypochlorite (the active ingredient in chlorine bleach) and hydrogen peroxide is as follows:

OCl- + H2O2 -> Cl- + H2O + O2

How much bleach neutralizer do I need to use?

Thiosulfate (Bleach Stop) is not as strong as Anti-chlor (sodium metabisulfite).

You need to use one whole ounce by weight (30 grams) of Bleach-Stop (sodium thiosulfate) per gallon of warm water, or a pound and a quarter for a twenty-gallon washing machine load — so, using your washing machine for this step would be very expensive and you'd better stick to a bucket, but you can do that. Cost per gallon of bleach neutralizing bath, 25¢. Not too expensive.

In contrast, you need only one teaspoon, or 2.2 grams, of Anti-chlor (sodium metabisulfite) per 2.5 gallons of water, or less than half a teaspoon per gallon of water. That works out to 18 grams per twenty-gallon washing machine load, if you like to use it there. Cost per gallon of bleach neutralizing bath, three-quarters of 1¢. Very, very inexpensive. Cheap enough even to use in the washer, if you're lazy about carrying buckets around, or if you want to use it as a regular laundry additive to reduce unwanted bleaching from chloramine in your water supply.

Buy whichever one your dye supplier sells, and be careful to use no less than their instructions say to. Rinse your garments in water quickly before neutralizing. ALWAYS fill your bucket or washing machine with rinse water to do this BEFORE you start to apply bleach to your fabric.

I'm not sure how much 3% hydrogen peroxide is absolutely required. I had good results by pouring half a bottle over my project; at $.79 per bottle, that was about 40¢ per use. Far less economical, but convenient for those times when you don't have any Anti-Chlor in the house and your next order isn't due to be delivered until next week. It works very well, too: although I had to leave that particular shirt in the bleach a long time to get my design, it never did develop any holes in the bleached part, over hundreds of washings. (There was no spandex or other synthetic fiber is the shirt, which helps a lot.) It eventually developed unrelated rips elsewhere on the shirt. I can certainly recommend 3% H2O2 as effective, even if not the most economical option.

Do I need to neutralize after using a reductive discharge such as Thiox?

No. You must neutralize after using chlorine (hypochlorite) bleach, but not after using reductive discharges such as Thiox, Formosul, or Rit Color Remover. You need only wash reductive discharge chemicals out with water. Any residual bisulfite or thiosulfate will react with the oxygen in the air and be safely destroyed.

Advertisements




Back to list of FAQs

 Home Page     Hand Dyeing Top     Gallery    About Dyes    How to Dye    How to Tie Dye    How to Batik    Low Water Immersion Dyeing    Sources for Supplies    Book Reviews    Other Galleries    Groups    FAQs     Custom Dyers    Forum    Q&A blog    link here    search    contact me  


Last updated: July 17, 2014
Page created: June 11. 2007
Downloaded: Tuesday, March 19, 2024

All of the pages on this site are copyright ©1998‑2024 Paula E. Burch, Ph.D.
Parts of this page originally appeared in the form of a posting by Paula Burch on the iTieDye Forum on June 11, 2007.

http://www.pburch.net/dyeing/FAQ//neutralizingdischarge.shtml