Bonding

The bag carries a single colour name. Dissolve it and use it for ice dyeing, and as the ice melts the colour can break apart into several colours spreading across the cloth. Dharma Trading Co., a dye retailer, explains that when a mixed colour (a colour made by blending dyes) is used for ice dyeing, the original pure colours split out as the melting ice pulls the dye through the fabric.^[1] Mixes of three or four colours, such as black, grey and brown, can split dramatically. Dharma also says that ice dyeing with pure colours, made from a single dye, is much less dramatic.^[2]

Beside a bag of dye there is usually another bag: soda ash (sodium carbonate). Explanations from the Kaken Test Center, a Japanese textile testing body, and others say that fixing a reactive dye to cloth needs an alkali such as this soda ash.^[1] What makes the colour of a reactive dye stop coming off the cloth? This theme follows that question through the covalent bond (a link formed when atoms share electrons) that a reactive dye makes with the fibre. At the end we return to the scene in which the colour splits apart on its way to becoming permanent.

The explanation that a reactive dye dyes by forming a covalent bond with the fibre agrees across four sources: the Kaken explanation, the dye retailer Dharma, the series "Dye Chemistry for Dyeing Technologists" (Part 3) written by Kunihiko Imada in the Journal of the Textile Machinery Society of Japan (in Japanese), and the technical pages of Iwase Shoten Co., Ltd. (Somelabo), a Japanese dye retailer.^[1] Imada says that the ways in which dye and fibre join in dyes for cellulose fibres fall into three modes. Reactive dyes dye through a stable covalent bond, which has the highest bond energy (a measure of how strong a link is) of the three. For this reason he explains that their fastness (resistance to colour loss or transfer) to water, sweat and washing is especially good.^[2] He also says that reactive dyes were announced in 1956 and are the newest of the dye classes.^[3] Nobuhiro Kiyoshima (formerly of Descente Ltd.), writing in "Apparel Sanpomichi", a column published by the Nissenken Quality Evaluation Center (in Japanese), likewise says that because reactive dyes bond covalently, their wet fastness (resistance to colour change and colour transfer in water, sweat and washing) is comparatively good. But they are not a cure-all. He notes reports that after long storage the dye can hydrolyse (react with water itself) through moisture in the air, and colour bleed (dye seeping out of the cloth and staining its surroundings) has occurred. He names fixative treatment as one countermeasure.^[4]

In Imada's account, the routes by which a dye joins the fibre fall broadly into two.^[1] He says that the aliphatic vinyl sulphone (sulphatoethylsulphone) joins cellulose fibre by a "nucleophilic addition reaction", and the heterocyclic monochlorotriazine by a "nucleophilic substitution reaction".^[2][3][2][4] This reaction competes with hydrolysis, in which the dye reacts with water itself. Imada states that under practical dyeing conditions the reaction with the fibre proceeds preferentially.^[5] If the dyeing temperature is above the optimum range, hydrolysis takes over and the fixation rate (the share of the dye used that ends up dyed onto the fibre) falls. If it is too low, the reaction with the fibre is delayed and fixation falls short, he adds.^[6]

Evidence for this paragraph (6)

[1]

reactive dye ・mechanismthe reaction mechanism with cellulosic fibre is broadly divided into nucleophilic addition and nucleophilic substitutioncontextual

1 source: 染色技術者のための染料化学（その3）2. 反応染料 · full evidence

[2]

reactive dye ・propertyreactive groups are classified by chemical structure into three types: aliphatic-carrier groups (vinyl-sulphone type), heterocyclic-carrier groups (mainly triazine and pyrimidine types), and bifunctional types carrying two or more different reactive groupscontextual

1 source: 染色技術者のための染料化学（その3）2. 反応染料 · full evidence

[3]

vinyl sulphone (sulphatoethylsulphone) group works by nucleophilic addition (reaction)contextual

Scope: Cellulosic fibre

Source: 染色技術者のための染料化学（その3）2. 反応染料 （今田邦彦, 2002） ・P120-P121 §2.2(2) ・textbook ・ checked against the source by AI

[4]

monochlorotriazine works by nucleophilic substitution (reaction)contextual

Scope: Cellulosic fibre

Source: 染色技術者のための染料化学（その3）2. 反応染料 （今田邦彦, 2002） ・P120 §2.2(2) ・textbook ・ checked against the source by AI

[5]

reactive dye works by hydrolysis (of reactive dye)contextual

1 source: 染色技術者のための染料化学（その3）2. 反応染料 · full evidence

[6]

reactive dye works by hydrolysis (of reactive dye)contextual

1 source: 染色技術者のための染料化学（その3）2. 反応染料 · full evidence

From Imada's explanation so far, this site takes it that the temperature at which each reactive group dyes best differs because of a tug-of-war with hydrolysis; a reactive group is the part of a dye molecule that reacts with the fibre. This is this site's reading. Imada's guide temperatures are about 40 to 50°C for the low-temperature type, 60°C for the mid-temperature type and 70 to 90°C for the high-temperature type. By reactive group, he gives 20 to 30°C for dichlorotriazine (DCT), the most reactive; 40 to 60°C for monofluorotriazine (MFT) and vinyl sulphone (VS); 75 to 80°C for monochlorotriazine (MCT); and 95°C for trichloropyrimidine (TCP), the least reactive.^{[1][2][3][4][5][6]} Procion MX, widely used for home tie-dye and ice dyeing, is placed in Imada's figure and tables in the low-temperature type: the most reactive, with the lowest dyeing temperature.^[7][8] Paula Burch, who writes explanations for makers, says that Procion MX is described as a dichlorotriazine dye with two chlorine atoms on its ring. She says these two chlorine atoms are the sites that react with the hydroxyl groups of cellulose. She also cautions that manufacturers often do not disclose dye structures, which makes them hard to confirm from the literature.^[9] Dharma explains that this cool-water dye reacts slowly, depending on temperature and pH. It also warns that too much heat can cause the colour to fail to bond.^[10] However, Imada's figures are guides for exhaust dyeing, in which cloth is dyed by immersing it in a dye solution. How far the same holds for ice dyeing, where the powder goes directly on the cloth and the temperature is that of ice, cannot be told from his explanation (see the questions at the end).

Evidence for this paragraph (10)

[1]

reactive dye ・propertyclassified by reactivity level into low-temperature type (40-50°C), mid-temperature type (60°C), and high-temperature type (70-90°C)contextual

1 source: 染色技術者のための染料化学（その3）2. 反応染料 · full evidence

[2]

dichlorotriazine ・propertyoptimum exhaust-dyeing temperature is 20-30°C, and it is shown as the most reactive of the reactive groups listed in table 11contextual

Scope: Exhaust dyeing

Source: 染色技術者のための染料化学（その3）2. 反応染料 （今田邦彦, 2002） ・P123 §2.5(1) 表11 ・textbook ・ checked against the source by AI

[3]

vinyl sulphone (sulphatoethylsulphone) group ・propertyoptimum exhaust-dyeing temperature is 40-60°C; the bond to fibre is stable to acid (pH 3-4), mild alkali (pH 9-10), heat (180°C) and oxygen bleach, but unstable to strong alkali (pH 13-14)contextual

Scope: Exhaust dyeing

Source: 染色技術者のための染料化学（その3）2. 反応染料 （今田邦彦, 2002） ・P123 §2.5(1) 表11; P126 §2.6 表21 ・textbook ・ checked against the source by AI

[4]

monofluorotriazine ・propertyoptimum exhaust-dyeing temperature is 40-60°C; the bond to fibre is stable to mild alkali (pH 9-10) but slightly unstable to acid (pH 3-4), strong alkali (pH 13-14), heat (180°C) and oxygen bleachcontextual

Scope: Exhaust dyeing

Source: 染色技術者のための染料化学（その3）2. 反応染料 （今田邦彦, 2002） ・P123 §2.5(1) 表11; P126 §2.6 表21 ・textbook ・ checked against the source by AI

[5]

monochlorotriazine ・propertyoptimum exhaust-dyeing temperature is 75-80°C; the bond to fibre is stable to mild alkali (pH 9-10) but slightly unstable to acid (pH 3-4), strong alkali (pH 13-14), heat (180°C) and oxygen bleachcontextual

Scope: Exhaust dyeing

Source: 染色技術者のための染料化学（その3）2. 反応染料 （今田邦彦, 2002） ・P123 §2.5(1) 表11; P126 §2.6 表21 ・textbook ・ checked against the source by AI

[6]

trichloropyrimidine ・propertyoptimum exhaust-dyeing temperature is 95°C, and it is shown as the least reactive of the groups listed in table 11; its bond to fibre is stable to acid (pH 3-4), mild alkali (pH 9-10) and heat (180°C), slightly unstable to strong alkali (pH 13-14), and quite unstable to oxygen bleachcontextual

Scope: Exhaust dyeing

Source: 染色技術者のための染料化学（その3）2. 反応染料 （今田邦彦, 2002） ・P123 §2.5(1) 表11; P126 §2.6 表21 ・textbook ・ checked against the source by AI

[7]

Procion MX (reactive dye brand) ・propertyin a figure ranking commercial reactive dye brands, placed at the highest-reactivity, lowest-dyeing-temperature endcontextual

1 source: 染色技術者のための染料化学（その3）2. 反応染料 · full evidence

[8]

Procion MX (reactive dye brand) ・typea low-temperature-dyeing type reactive dye (listed under DyStar); the guide temperature for the low-temperature type is 40–50°Ccontextual

1 source: 染色技術者のための染料化学（その3）2. 反応染料 · full evidence

[9]

Procion MX (reactive dye brand) bonds via dichlorotriazinecontextual

1 source: Frequently Asked Questions About Dyeing: structure of Procion MX dichlorotriazine dyes · full evidence

[10]

"Procion" type reactive dye ・mechanismStates the covalent reaction proceeds gradually depending on temperature and pH, and that too much heat can actually prevent this cool-water dye from bonding; recommends around 105°F for tub dyeing, and no less than 70°F for tie-dye/dye-painting methods that cure longercontextual

Scope: Procion-type reactive dye, per Dharma Trading Co.'s explanation

Source: Fiber Reactive Dye Chemistry （Dharma Trading Co.） ・冒頭「An explanation as to how the dye and associated chemicals work」の1〜2段落目 ・manufacturer statement ・ checked against the source by AI

According to the Kaken explanation, an alkali is also needed to drive the reaction with the fibre. After the fibre has taken up the dye from the dye bath, an alkali is added and the two are joined by a chemical reaction. Imada also says that adjusting the pH matters and that the type of alkali does not. He states that soda ash is widely used because adding about 10 to 20 g/L tends to bring the pH to around 11.5, which he gives as the optimum dyeing pH for the mid-temperature type.^[1][2] These figures concern exhaust dyeing. They are not statements about continuous dyeing, in which cloth is dyed while being fed through continuously, or about printing, in which a dye mixed into a paste is applied to the cloth in a pattern. Dharma and Burch explain that the role of soda ash is to raise the pH so that the fibre molecules can react with the dye.^[2] Dharma says that a pre-soak, in which the cloth is soaked in a soda ash solution beforehand, brings the pH of the cloth to about 10.5. It adds that this lets reactive dyes work at room temperature.^[3][4] Burch cautions that baking soda (sodium bicarbonate) is much less basic and will not substitute for soda ash in most dyeing recipes.^[5]

Evidence for this paragraph (5)

[1]

reactive dye requires alkalicontextual

2 sources: 反応染料; 染色技術者のための染料化学（その3）2. 反応染料 · full evidence

[2]

soda ash (sodium carbonate) ・mechanismraises pH so that the dye can react with the fibrecontextual

includes a limiting source; 4 sources: What is soda ash, and what's it for in dyeing?; Dharma's Fiber Reactive MX Dyes FAQ and 2 more · full evidence

[3]

soda ash pre-soak ・property ― pHcontextual

Scope: With Dharma's recipe (1 cup soda ash per gallon of water)

Source: Tie-Dye Instructions （Dharma Trading Co.） ・化学の説明の段落 ・manufacturer statement ・ checked against the source by AI

Source: Soda Ash Fixer (product page) （Dharma Trading Co.） ・分量の説明 ・manufacturer statement ・ checked against the source by AI

[4]

soda ash pre-soak ・propertylets fibre reactive dyes work at room temperature; heat can assist the reactioncontextual

Source: Tie-Dye Instructions （Dharma Trading Co.） ・化学の説明の段落 ・manufacturer statement ・ checked against the source by AI

Source: Soda Ash Fixer (product page) （Dharma Trading Co.） ・商品の説明 ・manufacturer statement ・ checked against the source by AI

[5]

baking soda (sodium bicarbonate) differs from soda ash (sodium carbonate)contextual

includes a limiting source; 3 sources: What is soda ash, and what's it for in dyeing?; Dharma's Fiber Reactive MX Dyes FAQ and 1 more · full evidence

The role of salt is separate from that of the alkali. Imada says that reactive dyes have a lower affinity for the fibre than direct dyes (affinity here means how readily, under given conditions, a dye stays on the fibre rather than in the liquid), so they need relatively large amounts of inorganic salt. The recommended amount in exhaust dyeing is about 50 to 80 g/L.^[1] In Dharma's tub dyeing method (dyeing in a tub or bucket), salt and dye load the dye onto the cloth. Dissolved soda ash is then added to raise the pH, and about one hour is allowed for fixing.^[2] For tie-dye and ice dyeing, where the powder goes directly on the cloth, Dharma says to soak the cloth in soda ash first.^[3] The order differs, but this site takes it that the role is the same: the alkali creates the conditions in which the reaction can take place. This is this site's reading.

Evidence for this paragraph (3)

[1]

reactive dye requires inorganic salt (exhaust-dyeing electrolyte)contextual

1 source: 染色技術者のための染料化学（その3）2. 反応染料 · full evidence

[2]

reactive dye ・mechanismin tub dyeing, salt and dye load the fabric, then dissolved soda ash raises the pH; the reaction takes about an hour to occur fullycontextual

1 source: Dharma's Fiber Reactive MX Dyes FAQ · full evidence

[3]

soda ash pre-soak ・propertyexample recipe: 1 cup soda ash per gallon of warm water (soda soak for tie-dye and ice dyeing)contextual

Scope: Dharma soda ash product page and tie-dye instructions

Source: Soda Ash Fixer (product page) （Dharma Trading Co.） ・"Soda Soak Method for Tie-Dye and Ice Dyeing" ・manufacturer statement ・ checked against the source by AI

Once the dye is on, the cloth is left for a set time. For tie-dye, Dharma explains, the cloth is kept damp in a plastic bag for at least 4 hours, or preferably 24 hours for the brightest colours. Below 70°F (about 21°C) it takes longer. For ice dyeing it likewise says to leave it for 24 hours.^[1][2] Another dye shop, PAC Fabric Dyes, says to leave the cloth unrinsed for 3 hours even after the ice has fully melted.^[3] None of these pages presents the times as a measurement. Dharma states that after 24 hours the sites on the cellulose where dye can bond should be filled with dye molecules. The excess dye that has not bonded is then washed away with a warm rinse and detergent.^[4] In the same company's tie-dye procedure, the cloth is first rinsed under cold running water with the ties still on. It is then untied and rinsed in lukewarm water until the water is almost clear, and put straight into the washing machine.^[5] In its ice dyeing procedure, the cloth is rinsed under cold running water until the water is almost clear, then machine-washed with hot water and dyer's detergent.^[6]

Evidence for this paragraph (6)

[1]

curing (batching) after dye application ・propertyat least 4 hours, preferably 24 hours for the brightest colours; below 70°F it takes longercontextual

Scope: Tie-dye; kept damp in a plastic bag

Source: Tie-Dye Instructions （Dharma Trading Co.） ・手順の放置の段 ・manufacturer statement ・ checked against the source by AI

[2]

curing (batching) after dye application ・propertylet sit for 24 hours; a warm place can speed things upcontextual

Scope: Ice dyeing; tubs covered with plastic

Source: Learn How to Ice Dye （Dharma Trading Co.） ・手順の放置の段 ・manufacturer statement ・ checked against the source by AI

[3]

ice dyeing ・propertyafter piling ice on the fabric and sprinkling on the dye, states that even if the ice melts sooner, the item should be left unrinsed for 3 hours to let the dye fix to the fabric (in one recorded example, at a room temperature of about 32°C, the ice took about 3 hours to melt)contextual

1 source: アイスダイタオル · full evidence

[4]

curing (batching) after dye application ・propertyafter up to 24 hours the bonding sites on the cellulose should be saturated with dye moleculescontextual

Scope: As explained by Dharma

Source: Tie-Dye Instructions （Dharma Trading Co.） ・化学の説明の段落 ・manufacturer statement ・ checked against the source by AI

[5]

rinsing and washout ・propertyrinse first in cold running water with ties on, then in warm water while untying until fairly clear, then machine-wash a full cycle at once; no more than about 8 adult tees at a timecontextual

Scope: Tie-dye

Source: Tie-Dye Instructions （Dharma Trading Co.） ・手順のすすぎの段 ・manufacturer statement ・ checked against the source by AI

[6]

rinsing and washout ・propertyrinse in cold running water until mostly clear, then machine-wash with hot water and dyer's detergentcontextual

Scope: Ice dyeing

Source: Learn How to Ice Dye （Dharma Trading Co.） ・手順のすすぎの段 ・manufacturer statement ・ checked against the source by AI

Washing out the dye that has not bonded affects how clear the colour is. Imada explains that before soaping (the step that washes away dye and other matter that has not bonded to the fibre), dye that has only hydrolysed, without reacting with the fibre, remains on the fibre. In this state wet fastness is poor, and removing it takes thorough soaping at 95 to 98°C for about 10 minutes.^[1][2] Burch says that a reactive dye that has been properly fixed and thoroughly washed out should not need a colour fixative in the first place.^[3] Katsuraya Fine Goods Co., Ltd. (Miyako-zome), a Japanese home-dye maker, also writes that its own reactive dye, "React", needs no colour fixing after dyeing.^[4] However, Burch writes that some industries, such as those where water use is restricted, sometimes use a cationic colour fixative (one with a positive electric charge) in place of thorough washing-out, to save cost.^[5] The sources thus contain both the view that a fixative is unnecessary and the view that it is sometimes used. How a colour fixative itself holds the dye is covered in the themes "Drawn by charge" and "Glued on".

Evidence for this paragraph (5)

[1]

reactive dye requires soaping (wash-off of unfixed reactive dye)contextual

1 source: 染色技術者のための染料化学（その3）2. 反応染料 · full evidence

[2]

soaping (wash-off of unfixed reactive dye) ・propertytypically carried out at 95-98°C for about 10 minutes, following a cold and warm rinse after dyeing; soaping at high temperature is effective, making temperature control especially importantcontextual

Source: 染色技術者のための染料化学（その3）2. 反応染料 （今田邦彦, 2002） ・P123 §2.5(1)(2) ・textbook ・ checked against the source by AI

[3]

post-dyeing colour-fixing agent is applicable to reactive dyecontextual

1 source: Is there a fixative that will make dye permanent? What is Retayne? · full evidence

[4]

Technique Dye React ・propertydyeing temperature 40-60°C; states that boiling water and post-dye colour-fixing are not requiredcontextual

Source: 技法用染料 リアクト CREATIVE DYE REACT（取扱説明頁） （桂屋ファイングッズ株式会社） ・商品説明冒頭・FAQ「染料の違いについて」 ・manufacturer statement ・ checked against the source by AI

[5]

post-dyeing colour-fixing agent is used in reactive dyecontextual

1 source: Is there a fixative that will make dye permanent? What is Retayne? · full evidence

The reactive groups of these dyes also have a property that calls for care. Imada, with the weighing and dissolving of dye powder in a dyeing plant in mind, explains that the reactive group can also react with the amino groups of proteins in blood. If dye that is still unreacted gets into the body, it can therefore cause sensitisation (the body becoming hypersensitive to a substance), such as allergy. Because sensitisation of the respiratory tract by inhaled dust can lead to life-threatening accidents, he says, major manufacturers display warning labels.^[1] A safety data sheet for one home-use dye (Jacquard's Procion MX, Lemon Yellow) likewise says that dyes of this type can cause respiratory sensitisation in some people. It advises avoiding inhaling aerosol or dust.^[2] Imada adds, however, that the concern about sensitisation applies only to dye that is still unreacted and active. He also says that dye in the dyed cloth or in dyeing effluent has already bonded to the fibre or hydrolysed, so it is not a problem.^[3]

Evidence for this paragraph (3)

[1]

reactive dye ・propertythe reactive group can also react with amino groups on blood proteins; if dye that has retained its reactivity is taken into the body, it can bond to those amino groups and cause allergic sensitisation, and inhaling dye dust can sensitise the respiratory tract in a way that can be life-threatening, so major manufacturers use warning labelscontextual

1 source: 染色技術者のための染料化学（その3）2. 反応染料 · full evidence

[2]

Procion MX (reactive dye brand) ・propertyIn its recommended-use notes, states that dyes of this type can cause respiratory restriction or sensitization in some individuals, advises avoiding breathing aerosol and dust, and states that people with asthma or breathing problems should not handle these dyescontextual

Scope: Home-use dye safety data sheet (Procion MX Lemon Yellow)

Source: Safety Data Sheet (SDS) — Procion MX 4-Color Set with Soda Ash（Lemon Yellow・Fuchsia・Turquoise・Jet Black・Soda Ash Dye Fixer各SDSを収録） （Rupert, Gibbon & Spider, Inc. (Jacquard Products), 2021） ・SECTION 1 - CHEMICAL, PRODUCT & COMPANY INFORMATION、Recommended Useの欄（Procion MX Dye - Lemon Yellow） ・manufacturer statement ・ checked against the source by AI

[3]

reactive dye works by hydrolysis (of reactive dye)contextual

Scope: Dyed fabric and dyeing effluent

Source: 染色技術者のための染料化学（その3）2. 反応染料 （今田邦彦, 2002） ・P126 §2.7(1) ・textbook ・ checked against the source by AI

The explanation so far holds for the combination of a reactive dye with cellulose fibres (cotton, linen, rayon and so on). Silk and wool change the story. Imada says that reactive dyes are also used on silk and wool. Dharma explains that on silk and wool the colours can shift, a true black is not possible, and mixes containing blue shift towards the colours of the other components.^[1][2][3] It also says that blue does not bond well with silk.^[3] On soda ash, Burch and Dharma's soda ash product page say it can be used on silk with caution, but that for wool acid dyes, which use heat or steam rather than soda ash, are better.^[4] Another Dharma page, its tie-dye instructions, says that wool and silk can also be dyed if the amount is halved and the wait kept to 4 to 6 hours. On wool, then, even the same company's pages disagree.^[4]

Vinegar, which helps dyeing of animal fibres, has a different role on cotton. Katsuraya Fine Goods explains that vinegar is an auxiliary that helps silk and wool take dye. It cautions that adding it when dyeing plant fibres such as cotton does not fix the colour and instead stops the dye taking.^[1] Burch also states that vinegar and salt are not colour fixatives, and that soaking already-dyed clothes in them will not set the dye.^[2] Neither source gives a chemical reason why it does not work on cotton.

Evidence for this paragraph (2)

[1]

vinegar ・why it fell out of usestates that adding vinegar when dyeing plant fibres such as cotton does not act as a colour-fixative, and instead prevents the dye from takingcontextual

Scope: Dyeing cotton with Katsuraya's Miyako-zome dyes

Source: 色止剤 ミカノールって？ （桂屋ファイングッズ株式会社, 2018） ・「それから、『お酢が色止め剤になる』と思って...」の段落 ・manufacturer statement ・ checked against the source by AI

[2]

vinegar differs from post-dyeing colour-fixing agentcontextual

Scope: As an after-treatment on already-dyed items

Source: Is there a fixative that will make dye permanent? What is Retayne? （Paula E. Burch, 2011） ・見出し「Vinegar and salt are not dye fixatives」 ・practitioner's record ・ checked against the source by AI

On the splitting of colours, known as colour splitting, Dharma gives as its reasons that dye molecules differ in size and that colours differ in how fast they strike (become permanent) in the presence of soda ash.^[1][2] This is the company's own explanation and rather than a finding from independent research. How to tell pure colours from mixed ones, and the relation to how wet the cloth is, are covered in the article "Colour splitting in ice dyeing".

Back once more to the boundary between the powder on the ice and the cloth after it has melted. This site takes that boundary to reflect, one by one, the conditions checked in this theme: whether the pH was high enough for the alkali to work, whether the dye was a pure colour or a mixed one, and whether the time and the temperature were sufficient. This is this site's reading. When several colours show up in one piece of cloth, the way of looking that this theme leaves you with is to work out which of these conditions was off.

• 🧪 Does the finished result differ between soaking in soda ash first and applying it afterwards?
• 🧪 Where does the figure of 48 hours for ice dyeing come from? The sources checked give 24 hours at most.
• 🧪 At the temperature of ice, how far does a low-temperature-type reactive dye actually react?
• 🧪 Why is it said that rinsing first in cold water "stops the reaction"? Practitioners give explanations, but they have not been verified.
• 🧪 Does the wetness of the cloth change how a mixed colour splits? (Testing Dharma's caution at home.)
• 🧪 Is a colour fixative needed? Compare colour transfer with and without one.
• Why vinegar stops cotton taking dye: Katsuraya Fine Goods and Burch describe only the phenomenon, and the sources give no mechanism. A newspaper column, on the other hand, carries a saying that in old households salt and vinegar were used to fix indigo dyeing, which conflicts with the specialists' accounts.
• 🧪 When the colour comes out pale, what is responsible? The sources offer several candidates, including pH, temperature and deterioration of the soda ash, but which of them matters, and by how much, under home conditions has not been confirmed.