How to bleach PFD fabric white

Name: Christopher

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Country or region: USA

Message: I cannot seem to find anywhere how to make Prepared For Garment Dye fabric white. i believe it is some combination of peroxide and bleach; but I have no idea how much of each and how long it should soak, and if I should use a special type of chemical. BTW- I purchased Bleach Stop thinking it would help. Thank you for any info you can provide me!

I have never seen a recipe combining peroxide and chlorine bleach, but both are used, separately, for this purpose. As a general rule it is dangerous to combine other chemicals with chlorine bleach, since ammonia-containing mixtures will produce chloramine gas, while acid-containing mixtures will produce chlorine gas, with potentially fatal results in either case. However, peroxide is not dangerous to mix with chlorine bleach. I still don't recommend bleaching fabric by mixing chlorine bleach with peroxide, though, unless you can find a reliable recipe specifying the details of how to do so.

It doesn't make sense to me to combine hydrogen peroxide and chlorine in a single treatment, because peroxide will react with hypochlorite to neutralize it. In fact, hydrogen peroxide, like Bleach Stop or Anti-Chlor, will neutralize hypochlorite by reacting with it to form less reactive chemicals. It will stop the bleaching action altogether, if you use enough of it. Hydrogen peroxide reacts with sodium hypochlorite to form sodium and chloride ions, water, and oxygen. See my page, "How can I neutralize the damaging effects of chlorine bleach?". I believe that bleach alone will be more effective than bleach combined with peroxide. However, following a bleach treatment with a peroxide treatment could make a lot of sense.

Although peroxide is much weaker at removing color than hypochlorite is, peroxide is popular in the textile industry for whitening the natural color of clothing fibers, because the environmental effects of disposal are less than for chlorine bleach, thus reducing costs in spite of the greater expense of peroxide as compared to that of chlorine. Peroxide can also be used on wool, something you should never do with chlorine bleach. PRO Chemical & Dye provides a mild recipe for bleaching white wool with hydrogen peroxide. Cotton should be able to tolerate harsher conditions than wool, especially high pHs, but I'm afraid I do not have a stronger recipe for peroxide-bleaching cotton.

"Color safe" oxygen bleaches are based on percarbonate or perborate, which are produced by reacting hydrogen peroxide with borates or carbonates; when cleaners such as Oxy-Boost or OxiClean are added to water, they generate hydrogen peroxide again, almost always without any effect on the color of the fabric. Much higher concentrations of peroxide are needed to bleach out the natural color. You won't be able to use the safe low concentrations of hydrogen peroxide available from a drug store; instead, you would need high concentrations of peroxide, 35% or more, which can be quite hazardous to work with if you don't have appropriate safety equipment.

Using chlorine bleach, which is based on hypochlorite, is recommended only for 100% natural plant fibers, such as cotton, linen, or hemp. Never use it on silk, wool, or synthetic fibers, such as nylon or spandex blends, which it will eat holes in. Even cotton can be damaged by using chlorine bleach that is too concentrated, or leaving it on for too long, or using it at too high a temperature, or failing to neutralize the bleach afterwards.

It would probably be best to bleach your fabric in a washing machine. This will expose you to the dangerous fumes much less than hand-bleaching of any sort (open a window in the laundry room if possible). If you work directly with chlorine bleach, I strongly advise you to buy a proper respirator, not a dust mask, with an acid gas cartridge, even if you're not mixing the bleach with anything else. Chlorine bleach is quite toxic and at high levels can do you harm, if you do not take precautions.

Don't pour the undiluted bleach directly onto the fabric. I'm not sure what quantity is best for this purpose; most of the instructions I've seen for whitening clothes call for using one or two cups of bleach, diluted with a quart of water before adding it, per load of clothing, waiting for the machine to fill with water before you add the bleach, and mixing the bleach with the water in the machine before adding the garments. These recommendations are not specifically for bleaching the natural color of cotton to a pure white, however, and may not be sufficient for your purposes.

Industrial hypochlorite bleaching of textiles makes use of between one and three grams per liter of available chlorine, according to A. K. Roy Choudery's book "Textile Preparation and Dyeing"; it appears that ordinary 5.25% sodium hypochlorite is referred to as if it contains 5.25% available chorine, in spite of the fact that it contains hypochlorite rather than chlorine, so one gram per liter would work out to 20% dilution (one part bleach to four parts water). That's quite a strong concentration of bleach!

Discharging color from dyed clothes may take as much as 25% bleach, diluted in water, but that process, when practiced by hand dyers, involves very small quantities of bleach, which makes it safer to work with. To achieve that concentration in a twenty-gallon washing machine load would require as much as five gallons of bleach, which does not seem to be a good idea. Commercial bleaching of fabric is done in stone or concrete containers; I suspect that the metal of a washing machine might be damaged by exposure to high concentrations of bleach.

I guess what I advise is that you try adding a few cups of household bleach to a washing machine with hot water, and then adding your clothes to it to see what happens after agitating gently for some time.

Your cotton should be clean before you try to bleach it, because hypochlorite will react with gray cotton to produce yellowing, according to John Shore's book, "Cellulosics Dyeing". Scouring the impurities from fabric that is obviously contaminated with plant material requires boiling it with soda ash or lye. Your garments have probably already been scoured before you received them.

Do not expect to obtain a perfectly bright white, no matter how much bleach you use. After successful bleaching, cotton fabric is lighter than its natural color, but it is still not perfectly white. In order to obtain the brightest whites, after all dyeing has been completed, you can using an optical brightener, which improves the whiteness by converting invisible ultraviolet light to a blueish light. Optical brighteners are more effective than blueing, which was the old traditional solution for slightly yellow cottons, because the additional light they make visible gives a "whiter than white" appearance. Dharma Trading Company sells an Optical Brightener which is ideal for this purpose, but many laundry detergents contain smaller amounts of a similar product.

After you have finished using chlorine bleach, it is wise to neutralize any remaining hypochlorite in the fabric. This is what the Bleach Stop (sodium thiosulfate) you bought is good for. You should wash out the bleach with water first, then soak your fabric for about fifteen minutes in a mixture of Bleach Stop and water. It is important to use enough Bleach Stop: you should use one ounce, or thirty grams, per gallon of water. Once you have used up your current supply of Bleach Stop, you might prefer in the future to buy Anti-Chlor (sodium metabisulfite), because less is required, so it's more economical; you need less than half a teaspoon of Anti-chlor per gallon, so it's more practical to use in a washing machine, which typically holds twenty gallons. PRO Chemical & Dye is one of the sources that sell Anti-Chlor.

For more information, see my pages, "How can I neutralize the damaging effects of chlorine bleach?" and "What chemicals can be used to remove dye?".

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Posted: Thursday - March 22, 2012 at 02:17 PM

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How to bleach PFD fabric white

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