About Color Remover

Sergio

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Hi guys,
i use sodium hydrosulphite to remove the red bleeding from wool oriental rugs. I found this page interesting by searching on google. Has anyone ever used these other chemicals? Is it sometimes advisable to use the other chemicals for this type of work?

I. Reductive Discharges


Sulfur dioxide, SO2, is the chemical that does the reducing, no matter which of the following chemicals you use to reduce your dye. Originally it was produced by burning yellow sulfur in the presence of the fiber to be bleached. This is probably not a good approach, for your own health; better to use one of the other reducing discharge agents to produce it on the fabric.


Thiourea dioxide (Colour Index Reducing Agent 11), also known as aminoiminomethanesulfinic acid or formamidine sulfinic acid, is sold under the brand names Thiox, Spectralite, Jacquard Color Remover, and Dharma Dyehouse Color Remover. The chemical formula is H2NC(=NH)SO2H. It is used in indigo dyeing and other vat dyeing as well as for discharge. It costs more than sodium hydrosulfite, but you use only one-fifth as much. Jacquard Color Remover contains Thiourea dioxide and soda ash. (Here's a link to PRO Chemical & Dye's instructions for using Thiox on cellulose, wool, and silk.) The solubility of thiourea dixodide is only 37 grams per liter at 20°C.


Sodium hydrosulfite (Colour Index Reducing Agent 1), also known as sodium dithionite, sodium sulfoxylate, and sodium sulphoxylate, is the active ingredient in Rit Color Remover
, Tintex Color Remover
, Dylon Run away for Whites, and Carbona Color Run Remover
, all of which also contain sodium carbonate (soda ash). Its chemical formula is Na2O4S2. This is the chemical used by Carter Smith in Kate Broughton's book Textile Dyeing: The Step-By-Step Guide and Showcase. Storage of large quantities is unsafe due to its flammability, but it is easy to find this product at local drugstores or sewing stores, so there is no need to buy a year's supply at once. You can use sodium hydrosulfite on the stovetop or in the washing machine; the latter is less effective but far more convenient for use on clothing.


Sodium hydroxymethanesulfinate (Colour Index Reducing Agent 2), also known as sodium formaldehyde sulfoxylate, sodium hydroxymethanesulphonate, sodium hydroxymethanesulfonate, and formaldehyde sodium sulphoxylate, is the chemical used in Formosul and Rongalit (most likely including BASF's Rongalit C and Rongalit ST, also sold as Jacquard Rongolit ST). Update: Also the active ingredient in deColourant Mist and deColourant Paste; see ProChem. Its chemical formula is CH3NaO3S. It can be used under acid as well as basic conditions. (Here is a link to PRO Chemical & Dye's instructions for using Formosul to strip color and discharge print on cotton, silk, wool and nylon.)


Zinc formaldehyde sulfoxylate (Colour Index Reducing Agent 6), Zn(HOCHSO2]2, is another discharge chemical, used commercially for screen-printing t-shirts.


Calcium formaldehyde sulfoxylate (Colour Index Reducing Agent 12), Ca(HOCH2SO2]2, is a discharge chemical that is manufactured in paste form. It is also the main ingredient in a different Rongalit product, Rongalite H, though I have not found a suitable source for it.


Other reductive discharge chemicals. Both sodium sulfite (Na2SO3) and sodium bisulfite (NaHSO3) are listed in some documents as reductive bleaches, but I cannot find a recipe for either's use for this purpose, though it's easy to find recipes for the use of the other reducing agents above. At our level it seems that these are only used to neutralize hypochlorite bleach. Do NOT confuse them with sodium bisulfATE (Na2SO4), which is used to destroy cellulose; remember the mnemonic, "bisulfATE ATE my fabric."


Jacquard Discharge Paste apparently contains Rongalit ST (see above), along with water, urea, and ammonia. This product is highly recommended by dyers who like the convenience of not having to make their own paste and like its stable shelf life. To use it, you paint or print your design on fabric, allow to dry, and then steam-iron to activate the reaction. (Here is a link to Jacquard Products' instructions for using three different kinds of discharge paste: thiourea dioxide print paste, Rongalit print paste, and Jacquard Discharge paste.)


Tin(II) chloride is unlike the above reductive discharges in that it does not involved sulfur dioxide at all. Also known as "tin salt", it has a formula of SnCl2•2H2O, and has been used in discharge printing on wool. It reacts to form hydrochloric acid in the steamer, which is corrosive to the equipment. It must not be used with thiodiglycol as a dye solvent, because the reaction of hydrochloric acid with thiodiglycol produces deadly mustard gas. (Source: David M Lewis, Wool Dyeing.)

Heating

All of the reductive discharge chemicals require heat to activate the reaction that breaks the double bonds in the dye chemicals. Some recipes call for hot tap water in the washing machine; most call for the higher temperatures of a discharge bath (heated in a cooking pot), a steamer, or heating with a steam iron.


An alternative way to provide the moist heat required to activate discharge agents is to steam your treated items in a spare microwave oven that has been placed out-of-doors during use. It is recommended that you use a microwave oven that you will not be using for food. Do not microwave dry fabric, as it will burn. Wrap damp fabric in plastic so that it will not dry out as it cooks, or place a cup of water in the microwave while you use it. Do not use a microwave that is indoors for heating discharge chemicals, as the irritating fumes produced can be bad for your lungs.

Cautions

Although the reductive discharge chemicals are less toxic, in general, than chlorine bleach, they all produce sulfur dioxide, which may be particularly dangerous for people who have asthma. All should be used only with gloves and with care to avoid overexposure to any vapors produced. Be sure to use proper ventilation and/or an acid gas respirator while working with them. Note that a dust mask provides no protection at all. Obtain and read the MSDS (materials safety data sheet) for each chemical you work with.


Sulfur dioxide fumes may also have undesirable effects on fabrics that have been dyed with indigo or other vat dyes, causing blues to turn yellow or green. Do not leave indigo-dyed fabrics exposed to the air in a room in which you are using any reductive discharge chemical.
 
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Sergio

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I can easily find thiourea dioxide online. When can it be used to replace sodium hydrosulphite?
 

Sergio

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What do you think about it?
"Thiourea dioxide is a reducing agent for indigo and other vat dyes and is an excellent substitution for sodium hydrosulfite in color stripping and discharge. It is safer to use, has a greater strength, and has a better shelf life. It can be used for stripping cellulose fiber or bleaching wool or silk. It must be used in a well ventilated area or outside. "
 

Sergio

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Why Customers choose Thiourea Dioxide(TDO):
Sodium Hydrosulfite is being used in the textile industry as a reducing agent
for dyeing vat and sulfur vat dyes; as a reducing-washing agent for fabrics
dyed with dispersion dyes; as a decolorizing agent for dyed fabrics; as a
bleaching agent for wool, silk and polyamide fabrics; etc. However, various
handling problems are inherent in its use such as unstable storage life in
powdered form, generation of obnoxious sulfurous acid gas, adsorption of
moisture, generation of heat when in contact with water and possibility of
igniting. Furthermore, since it decomposes very quickly in aqueous solution,
there is an added disadvantage of requiring several times more than its
theoretical amount. Its decomposition in chemical solution during storage for
use in continuous dyeing of vat and sulfur vat dyes is also so great as to
present considerable difficulties in maintaining its concentration.
We take great pleasure, therefore, in introducing to you our TDO, a reducing
agent for overcoming all these difficulties mentioned above with Sodium
Hydrosulfite.

Special Characteristics of TDO
1. Since it is a white powder incapable of any oxidative or reductive action
alone, TDO has a very stable storage life.
2. TDO is not hygroscopic and is absolutely free from deliquescence of
caking.
3. TDO does not generate heat when in contact with water or ignite under
impact.
4. TDO does not emit obnoxious sulfurous gas like Sodium hydrosulfite.
5. Preparation of solution with TDO is simplified since far less amount is
required than with Sodium Hydrosulfite.
6. An aqueous solution of TDO is not only very stable when stored but also
when on fabrics regardless of what the PH is. Hence process and quality
controls in continuous dyeing, bleaching, reducing-washing and
decolorizing operations are easy and dependable.
7. TDO shows very high reduction potential in aqueous solution. Hence
dyes difficult to reduce and decolorize with Sodium Hydrosulfite are
possible with TDO. Furthermore, wool can be bleached to a high level
of brightness with TDO. However, when using TDO as a reducing agent
in dyeing vat dyes, an anti-reducing agent is necessary for preventing
excessive reduction of indanthrone based dyes.
8. In bleaching wool with TDO, uniform dyeing is obtained due to its slow
decomposition in bleaching solution. Moreover, TDO can be used in
continuous steam bleaching with far less shrinkage and damage than
with Sodium Hydrosulfite.
9. It does good to the environment, not increase waste water pollution load,
and conforms to the environmental protection requirements---save
production cost.
 

Hack Attack

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If you are using sodium hydrosulphite with success why change?


"Sulfur dioxide, SO2, is the chemical that does the reducing, no matter which of the following chemicals you use to reduce your dye."
 
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Sergio

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Becouse I get excellent results with red. I have some difficulties with blue and green colors. Thiourea dioxide can help me?
 

Sergio

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Is there any known difference between sodium hydrosulphite and sodium dithionite?
 

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