Name: Chrissy


Message: Hi there! I'm planning on making bleach designs on a lot of shirts and I've done a lot of web research on the topic. I'm 99% done. All I'm wondering, is for the neutralizing step with the anti-chlor, if I have a bucket with the water/anti-chlor mix in it, about how many shirts do you think I could put in it at a time, or individually, and how many times could I use the same bucket of solution? Does it need to be refreshed with clean water and new anti-chlor from time to time? You seem to have all the answers so I hope you can help me. I can't find any suggestions anywhere on the web.

Hi Chrissy,

The Anti-Chlor does get used up as you go. You should, however, rinse your shirts carefully in plain water before placing them into the Anti-Chlor bath. This will considerably reduce the amount of hypochlorite that goes into your neutralizing bath. Otherwise, you would need to use far more Anti-Chlor. Using a larger quantity of Anti-Chlor would also mean that you would experience far more of the reaction products in your air, which could be a problem if you have asthma. Many people with asthma are sensitive to sulfites.

ProChem says to start with one teaspoon (2.2 grams) of their Anti-Chlor (sodium metabisulfite) per 2.5 gallons of water. (If you use Bleach Stop, or thiosulfate, instead of Anti-chlor, you'll need to use a much greater quantity, 30 grams per gallon.) This is described on my page on "How can I neutralize the damaging effects of chlorine bleach?". 

The question of how frequently you would need to refresh your Anti-Chlor bath depends on how much stuff you are neutralizing. To get a lower limit of how far the Anti-Chlor will go, let's see how much Anti-Chlor it would take to react with a certain amount of unrinsed household bleach. Unfortunately, I have been unable to determine the exact chemical reaction between the bisulfite of the Anti-Chlor and the hypochlorite of the bleach, but let's assume that one molecule of Anti-Chlor will react with one molecule of hypochlorite. In one-quarter cup of household bleach, at 5%, there will be about 3 grams of sodium hypochlorite molecules. The number of hypochlorite molecules in one-quarter cup (59 ml) of household bleach is about 0.04 moles (a unit of a certain number of molecules), which works out to be the same as the number of moles of sodium metabisulfite in 7.5 grams of Anti-Chlor. How much household bleach did you start out with? How much household bleach was used, on average, in producing each shirt?

Practically, though, if you rinse your shirts well, before putting them into the Anti-Chlor, you will need only a tiny fraction as much Anti-Chlor to neutralize it.

You cannot save your Anti-Chlor solution from one day to another, so these calculations are only for when you are working with a large number of items at once. The sodium metabisulfite in the Anti-Chlor not only reacts with the hypochlorite in the bleach, it also reacts with the oxygen in the air. This means that Anti-Chlor solutions "go bad" after a while and should be prepared just before use. This fact is convenient when you are preparing water for use in an aquarium, because water that has been treated with Anti-Chlor to remove the chlorine so that fish can live in it must also be free of Anti-Chlor itself; simple exposure to air will break down the sodium metabisulfite.

If you have reason to avoid the use of sulfites, then a perfectly effective and safe alternative is to use the 3% hydrogen peroxide which is sold at pharmacies for use as an antiseptic. The reaction between hydrogen peroxide and hypochlorite bleach produces safe chloride ions in the water, plus it produces water molecules, and oxygen molecules (the source of the bubbles you see). Hydrogen peroxide is a little less economical than Anti-Chlor, but not hugely expensive, and in my experience protects the fabric extremely well against continued degradation by the hypochlorite. 

I recommend against the outdated practice of using an acid such as vinegar to neutralize bleach, because it may produce chemicals that are even more caustic to the fabric, or even to your lungs; stronger acids than vinegar are known to produce dangerous amounts of chlorine gas when they react with hypochlorite.

(Please help support this web site. Thank you.)