Dissolving in

The usage guide for the black-dyeing service KUROZOME REWEAR, run by Kyoto Montsuki Co., Ltd., says that when a white garment is dyed black, the sewing thread may remain as white stitching. The same guide says that sewing thread and buttonhole stitching are often polyester, and that these parts stay their original colour.^[1]

Evidence for this paragraph (1)

[1]

KUROZOME REWEAR ・propertySewing thread, embroidery thread and buttonhole stitching are said to often be polyester, and that part is reported to stay its original colour even after black dyeing; for example, a garment originally white and dyed black is said to end up with the sewing thread showing as white stitching. Gold and silver thread are said to sometimes break or discolour.contextual

Scope: The KUROZOME REWEAR black-dyeing service

Source: ご利用方法（素材・注意事項を含む） （株式会社京都紋付（KUROZOME REWEAR【K】）） ・「注意事項」中「・縫製糸について」の項 ・manufacturer statement ・ checked against the source by AI

A home-dye product page shows a similar situation. The product page for Cooldye Hot, from Katsuraya Fine Goods Co., Ltd. (Miyako-zome), lists "none" under auxiliaries for polyester, and places polyester in the category that dyes only "lightly" unless a colour-deepening accelerator is added. The page says that to dye polyester to a deep shade, you need to add the accelerator and dye with heat.^[1]

Evidence for this paragraph (1)

[1]

Cooldye Hot ・requiresStates that dyeing polyester to a deep shade with Cold Dye Hot requires adding a colour-deepening accelerator and heating the bath, and that neither the salt used for plant fibres nor the vinegar used for animal fibres is needed for polyester; without the accelerator, polyester takes up only a pale colour.contextual

Scope: Dyeing polyester with Cold Dye Hot (Katsuraya Finegoods)

Source: 【公式】コールダイホット - お湯で濃く染まる （桂屋ファイングッズ株式会社（みやこ染）, 2026） ・MATERIAL 染まるもの／HOW TO 染め方 3.素材ごとの助剤 ・manufacturer statement ・ checked against the source by AI

Both guides show a case where the way a dye takes depends on the type of fibre. In the Kyoto Montsuki guide, the sewing thread, often polyester, keeps its original colour. On the Cooldye Hot page, polyester falls into the category that takes only a pale colour without an auxiliary. This site's reading is that a single class of dyes, disperse dyes, is involved at this boundary. However, as we will see later, it has not been confirmed whether Cooldye Hot is a dye of this class. We will check this against sources below.

Within the range this site has checked, the dyes used for cotton do not dye polyester. So how does a dye made specifically for polyester get inside the fibre, and how does it stay there?

The Kaken Test Center, a Japanese textile testing foundation, describes disperse dyes as "dyes that do not dissolve in water".^[1] Kaken goes on to say that the dye is scattered finely in the water by the action of a dispersing agent (a surfactant), and that the small amount of dye molecules that dissolve are what dye the fibre.^[2] Kunihiko Imada defines them in a similar way in Part 8 of his series "Dye Chemistry for Dyeing Technologists" in the Journal of the Textile Machinery Society of Japan (in Japanese). Dyes that hardly dissolve in water and are used to dye hydrophobic fibres (fibres that do not take up water readily), such as acetate and polyester, are called disperse dyes.^[2] Kaken says this class can dye polyester, acetate, nylon, acrylic, vinylon and polyurethane.^{[3][4][5][6][7][8]}

Evidence for this paragraph (8)

[1]

disperse dye is insoluble in watercontextual

Scope: nearly insoluble

Source: 分散染料 （一般財団法人カケンテストセンター） ・本文1〜2文目 ・institutional summary ・ checked against the source by AI

[2]

disperse dye works by dyeing from a dispersion of sparingly soluble dyecontextual

Source: 分散染料 （一般財団法人カケンテストセンター） ・本文1〜2文目 ・institutional summary ・ checked against the source by AI

Source: 染色技術者のための染料化学（その8）7. その他合成繊維用染料 7.1 分散染料 （今田邦彦, 2003） ・P181 §7.1 1) ・textbook ・ checked against the source by AI

[3]

disperse dye is applicable to polyestercontextual

Source: 分散染料 （一般財団法人カケンテストセンター） ・本文「…に染色可能」 ・institutional summary ・ checked against the source by AI

[4]

disperse dye is applicable to acetatecontextual

Source: 分散染料 （一般財団法人カケンテストセンター） ・本文「…に染色可能」 ・institutional summary ・ checked against the source by AI

[5]

disperse dye is applicable to nyloncontextual

Scope: As stated on Kaken's short explainer page; no test conditions or sources are given

Source: 分散染料 （一般財団法人カケンテストセンター） ・本文「…に染色可能」 ・institutional summary ・ checked against the source by AI

[6]

disperse dye is applicable to acryliccontextual

Scope: As stated on Kaken's short explainer page; no test conditions or sources are given

Source: 分散染料 （一般財団法人カケンテストセンター） ・本文「…に染色可能」 ・institutional summary ・ checked against the source by AI

[7]

disperse dye is applicable to vinyloncontextual

Source: 分散染料 （一般財団法人カケンテストセンター） ・本文「…に染色可能」 ・institutional summary ・ checked against the source by AI

[8]

disperse dye is applicable to polyurethanecontextual

Source: 分散染料 （一般財団法人カケンテストセンター） ・本文「…に染色可能」 ・institutional summary ・ checked against the source by AI

In the same article, Imada also lists structural features that disperse dyes share. Their molecules have no easily water-soluble groups, such as sulphonic acid or carboxylic acid groups, and their molecular weight is roughly 250–750, smaller than that of other dye classes. Precisely because they have nothing that makes them dissolve, he says, dye makers grind them into fine particles beforehand and finish them as products that disperse readily in water in a colloidal state (an extremely fine suspension of particles that do not settle out).^[1]

Evidence for this paragraph (1)

[1]

disperse dye ・propertyStates that because disperse dyes have no water-soluble groups such as sulfonic or carboxylic acid groups in their molecular structure, using the dye substance as-is cannot give a uniform dye bath and practical dyeing is impossible; industrially, therefore, dye makers pre-grind the dye into fine particles supplied as a product that readily forms a colloidal dispersion in water. It also lists as common structural features of disperse dyes: no water-soluble group, a molecular weight of roughly 250-750 (smaller than other dye classes), and an inorganic/organic ratio of roughly 0.6-1.0 (versus about 0.7 for polyester fibre itself).contextual

Scope: Structural features of disperse dyes

Source: 染色技術者のための染料化学（その8）7. その他合成繊維用染料 7.1 分散染料 （今田邦彦, 2003） ・P181-182 §7.2；P184 §7.3 ・textbook ・ checked against the source by AI

On reactive dyes, which dye cotton, Dharma Trading Co. says they suit natural fibres such as cotton, rayon, wool and silk, but will not dye synthetics.^[1] In the part of the same series that covers reactive dyes, Imada says that in polyester/cotton blends, reactive dyes are used on the cellulosic-fibre side.^[2] In the range this site has read, neither source explains why the synthetic side does not take the dye.

The practitioner Paula Burch explains that ready-made clothing is often sewn with polyester thread, and that dyes meant for cotton and other natural fibres do not colour polyester, so a dedicated dye class, disperse dye, is needed.^[1] For thread that will not take the dye, she also suggests looking for garments sewn with thread that does dye, or dyeing the fabric first and having it sewn with thread that matches.^[2] This site's reading is that the white stitching in the opening scene is an example of this boundary showing up on a product.

Evidence for this paragraph (2)

[1]

polyester is insoluble in disperse dyecontextual

Scope: Sewing thread in ready-made clothing

Source: Dyeing thread in pre-sewn clothing (How can I get the thread to dye, too?) （Paula E. Burch, 2006） ・「Polyester thread」の段落冒頭 ・practitioner's record ・ checked against the source by AI

[2]

polyester ・propertyAs alternatives to unavoidably undyeable thread, suggests finding garments made with dyeable thread, or dyeing yardage first and hiring a seamstress to sew it with thread matching the dyed fabric colour; also notes that some garments look fine left with white thread, since it can read as decorative stitching added after dyeing.contextual

Scope: Overdyeing ready-made garments (workarounds for sewing thread that will not take the dye)

Source: Dyeing thread in pre-sewn clothing (How can I get the thread to dye, too?) （Paula E. Burch, 2006） ・"Alternatives"の節 ・practitioner's record ・ checked against the source by AI

In its technical guide "Kayalon Polyester Dyes: Dyeing Technical Guide" (in Japanese), Nippon Kayaku describes how polyester is dyed with disperse dyes at high temperature in industry. A sealed, pressure-rated dyeing machine is used, and a mildly acidic dye bath (about pH 4.5–5; the liquid holding the dye and auxiliaries) is heated from around 60°C to 120–135°C. For regular-type polyester the temperature is usually 130°C. The bath is held at that temperature for 30–90 minutes. Nippon Kayaku adds, however, that the proper dyeing temperature varies with factors such as the fibre material, the dye type and the weave structure.^[1] Imada likewise gives standard dyeing temperatures that differ by fibre: polyester 130°C, triacetate 120°C, nylon and acrylic 100°C, and acetate 80–100°C.^[2]

Evidence for this paragraph (2)

[1]

disperse dye ・requiresDescribes industrial high-temperature disperse dyeing as using a sealed, pressure-rated dyeing machine: a bath adjusted to a mildly acidic pH (about 4.5-5) is raised from around 60°C to 120-135°C (usually 130°C for regular-type polyester) over 30-60 minutes and held there for 30-90 minutes, typically about 60.contextual

Scope: Industrial high-temperature disperse dyeing of polyester

Source: カヤロン ポリエステル染料 染色技術解説 （日本化薬株式会社, 2002） ・3-2-5. 高温染色 ・manufacturer statement ・ checked against the source by AI

[2]

disperse dye requires High-temperature exhaust dyeing method for polyestercontextual

Scope: High-temperature exhaust dyeing of polyester etc. with disperse dyes

Source: 染色技術者のための染料化学（その8）7. その他合成繊維用染料 7.1 分散染料 （今田邦彦, 2003） ・P184 §7.4-7.6(1)図 ・textbook ・ checked against the source by AI

Imada also presents a different method, carrier dyeing. It uses a carrier (an auxiliary) at 4 g/L, together with acetic acid (pH 5) and so on; the bath is held at 60°C for 20 minutes, then heated to 98–100°C and held for 60–90 minutes. In the range this site has read, however, the article does not explain how the carrier makes dyeing possible at normal pressure.^[1] Presenting this as a method that does not use sealed, high-pressure equipment is this site's reading.

Evidence for this paragraph (1)

[1]

disperse dye requires Carrier dyeing methodcontextual

Scope: Carrier dyeing method for polyester

Source: 染色技術者のための染料化学（その8）7. その他合成繊維用染料 7.1 分散染料 （今田邦彦, 2003） ・P185 §7.6(1)② ・textbook ・ checked against the source by AI

In another part of the same technical guide, Nippon Kayaku says that most carriers (the same thing as the carrier mentioned above) sharply lower light fastness (how well the colour resists fading in sunlight and the like) if they stay in the cloth. For that reason they must be driven off by dry-heat treatment at 150–180°C.^[1] For after-treatment, it says that reduction clearing (washing in a liquid containing a reducing agent, to remove dye left on the fibre surface) is normally carried out straight away, to remove unfixed dye and dirt.^[2] It lists three dyeing auxiliaries (chemicals that help the dyeing): a dispersing agent that keeps the dye dispersed, a levelling agent that reduces uneven dyeing, and a sequestrant that prevents discolouration caused by metal ions.^[3]

Evidence for this paragraph (3)

[1]

polyester ・causesStates that most carrier agents used in carrier dyeing of polyester markedly lower light fastness if they remain on the dyed fabric; washing alone is insufficient to remove them, and dry-heat or steam treatment (volatilising/subliming the carrier) is needed, with dry-heat treatment at 150-180degC for about 30 seconds to 3 minutes restoring light fastness close to its original level.contextual

Scope: This manufacturer's technical-manual description of carrier dyeing of polyester

Source: カヤロン ポリエステル染料 染色技術解説 （日本化薬株式会社, 2002） ・「3-2-6. キャリヤー染色」該当箇所 ・manufacturer statement ・ checked against the source by AI

[2]

disperse dye ・requiresStates that after disperse dyeing, a reduction-clearing wash is normally carried out next, which removes unfixed dye, surface staining and dirt from the dyed goods, giving good rub and wet fastness and a clearer shade.contextual

Scope: Post-treatment after Kayalon Polyester disperse dyeing

Source: カヤロン ポリエステル染料 染色技術解説 （日本化薬株式会社, 2002） ・3-2-9. 後処理 ・manufacturer statement ・ checked against the source by AI

[3]

disperse dye ・propertyLists three auxiliaries used in disperse dyeing -- a dispersant to keep the dye suspended in water, a levelling agent to reduce uneven dyeing, and a metal-ion sequestrant to prevent discolouration from metal ions -- describing each as serving a distinct role.contextual

Scope: Auxiliaries used in Kayalon Polyester disperse dyeing

Source: カヤロン ポリエステル染料 染色技術解説 （日本化薬株式会社, 2002） ・3-2-10. 染色助剤 i)〜iii) ・manufacturer statement ・ checked against the source by AI

With home dyes, the situation is a little different. Jacquard Products describes how to use iDye Poly: a dye in a dissolvable packet is dropped into a pot of hot water, the fabric or object to be dyed is added, and the pot is brought to a simmer.^[1] The company presents iDye Poly as virtually the only dye that will colour polyester, and says it can colour almost any synthetic material, including nylon, plastics and wigs.^[2] For blended fabrics, it says, the dye can be used in the same dye bath as iDye for natural fibres, and it says iDye Poly can also be used for sublimation-transfer work and for colouring the polyester thread that ready-made clothing is sewn with.^[3]

Evidence for this paragraph (3)

[1]

iDye Poly ・requiresStates the dye comes in a dissolvable packet: drop the packet into a pot of water, add the fabric or object, and bring to a simmer.contextual

Scope: How to use iDye Poly

Source: iDye Poly（商品ページ） （Jacquard Products） ・商品ページ本文 ・manufacturer statement ・ checked against the source by AI

[2]

iDye Poly is applicable to polyestercontextual

Scope: Materials iDye Poly can dye

Source: iDye Poly（商品ページ） （Jacquard Products） ・商品ページ本文冒頭 ・manufacturer statement ・ checked against the source by AI

[3]

iDye Poly ・used inStates that for blended fabrics, using iDye for Natural Fabrics together with the corresponding iDye Poly colour in the same dye bath colours both fibre types at once. Also mentions two further uses: sublimation-transfer work, and colouring the polyester thread that store-bought clothing is often sewn with.contextual

Scope: Applications and use of iDye Poly

Source: iDye Poly（商品ページ） （Jacquard Products） ・商品ページ「カラー一覧」欄外の注記 ・manufacturer statement ・ checked against the source by AI

The glossary page on the same company's website gives iDye Poly as an example of a disperse dye (the entry is titled "Disperse dye"). It also says that disperse dyes have the unusual property of sublimating (a solid turning directly into a gas without becoming a liquid) even though they do not dissolve in water.^[1] In the main text of a page about direct dyes, Burch also describes the company's iDye as a line of direct dyes and iDye Poly as a line of disperse dyes.^[2]

Evidence for this paragraph (2)

[1]

iDye Poly is a type of disperse dyecontextual

Scope: Jacquard Products' own website Glossary page, entry "Disperse dye"

Source: Jacquard Products - Glossary （Jacquard Products (Rupert, Gibbon & Spider, Inc.)） ・Glossaryページ、D項目「Disperse dye」の定義文 ・manufacturer statement ・ checked against the source by AI

[2]

iDye Poly ・differenceIn the body of the page "About Direct Dyes", Burch writes of Jacquard Products' iDye as a line of direct dyes and of the company's iDye Poly as a line of low-energy disperse dyes. The page says the two can be mixed to colour cotton/polyester blends in one dyebath, and that although iDye comes with washing-machine instructions, colouring polyester or blends with iDye Poly means boiling on the stovetop.contextual

Scope: As one paragraph of the body of the page "About Direct Dyes" of Burch's hand-dyeing site (shown as updated December 2009), in the section on where to buy direct dyes. It is written in the first person and sits outside the page's advertisement boxes. For iDye Poly it mentions only polyester and blends, not nylon, acrylic or acetate. It does not say whether the term disperse dye comes from the company's description or from the writer's own check. The same paragraph says the writer does not know which individual dyes iDye contains, that the company calls them all proprietary blends, and that no lightfastness or washfastness data are therefore available. It describes no dyeing conditions or tests of the result

Source: About Direct Dyes （Paula E. Burch, 2009） ・「where to buy direct dyes」の節の、Jacquard Productsの商品を述べる段落 ・practitioner's record ・ read by AI (not yet checked)

The product page for Polyester Dye from Katsuraya Fine Goods (Miyako-zome), on the other hand, says that it must be used with heat at about 90°C, that the supplied colour-deepening accelerator must be added, and that a heat-resistant container is needed.^[1] In none of the product pages this site has checked is this dye stated to be a disperse dye. The same is true of Cooldye Hot. Katsuraya Fine Goods also says that Polyester Dye dyes polyester to a deeper shade than Cooldye Hot does.^[2]

Evidence for this paragraph (2)

[1]

Polyester Dye ・requiresDescribes the product as a set of 20g powder dye (in a plastic container) and 20g colour-intensifying booster (in a film bag, with instructions), requiring heated dyeing at about 90°C with the booster added, and a heat-resistant container prepared. States it comes in 14 colours which can be mixed, and is an ECO dye free of designated hazardous chemicals. The product page text does not use the words 'disperse dye' and gives no dye class name (acid, direct, reactive and so on).contextual

Scope: Miyako-zome Polyester Dye product page (the seller's own guidance). The page gives no dye class name

Source: ポリエステルダイ（商品ページ） （桂屋ファイングッズ株式会社（みやこ染）） ・商品ページ本文 ・manufacturer statement ・ checked against the source by AI

Source: ポリエステルダイを使ったポリエステル100％素材の染め方を動画でご紹介 （桂屋ファイングッズ株式会社（みやこ染）, 2020） ・染色を始める前に確認すること・準備するもの ・manufacturer statement ・ checked against the source by AI

[2]

Polyester Dye is applicable to polyestercontextual

Scope: Materials Miyako-zome Polyester Dye can dye

Source: ポリエステルダイ（商品ページ） （桂屋ファイングッズ株式会社（みやこ染）） ・商品ページ本文冒頭の説明文（箇条書き）および「染められる素材」欄 ・manufacturer statement ・ checked against the source by AI

What follows is this site's reading. A home pot is an open pot at normal pressure, and the conditions differ from the sealed dyeing at 120–135°C that Nippon Kayaku describes for industry.^[1] In the range this site has searched, we have found no material in which a company itself explains how its home products dye polyester under these conditions. For iDye Poly, Jacquard Products itself and Burch both call it a disperse dye. For the two Miyako-zome products (Polyester Dye and Cooldye Hot), by contrast, whether they dye by the same mechanism remains an unconfirmed question.

Evidence for this paragraph (1)

[1]

disperse dye ・requiresDescribes industrial high-temperature disperse dyeing as using a sealed, pressure-rated dyeing machine: a bath adjusted to a mildly acidic pH (about 4.5-5) is raised from around 60°C to 120-135°C (usually 130°C for regular-type polyester) over 30-60 minutes and held there for 30-90 minutes, typically about 60.contextual

Scope: Industrial high-temperature disperse dyeing of polyester

Source: カヤロン ポリエステル染料 染色技術解説 （日本化薬株式会社, 2002） ・3-2-5. 高温染色 ・manufacturer statement ・ checked against the source by AI

The Jacquard Products glossary said that disperse dyes sublimate even though they do not dissolve in water. This property can work for good or ill; that is this site's reading. Below we look, in turn, at an example where it works badly and one where it is used deliberately.

As an example of the unwelcome side, the BOKEN Quality Evaluation Institute, a Japanese textile testing foundation, describes a phenomenon called thermal migration. Disperse dyes used on polyester move to the fibre surface under high temperature, which leads to colour transferring (migrating) to other fabric in contact. It says the smaller the dye particles, the more readily this happens.^[1] As reported accidents, BOKEN gives a case where red colour migrated onto white fabric that had been stored stacked with it, and cases where migration was found after container transport or after goods were taken out of a car in summer.^[2]

In "Apparel Sanpomichi" ("Apparel Stroll"; in Japanese), a column published by the Nissenken Quality Evaluation Center, a Japanese textile testing foundation, Kiyoshima (formerly of Descente Ltd.) describes a case where a white pigment print (a design fixed on cloth with a resin) on a dark polyester shirt turned pink while in stock.^[1] As countermeasures, Kiyoshima lists checking in advance with a sublimation fastness test (JIS L 0854; fastness here means how well colour resists changing or transferring to other fabrics when heated), reduction clearing, and the use of thin interleaving paper (anti-sublimation paper). Kiyoshima says the basic test condition is 120°C for 80 minutes, though some companies use other conditions.^[2] Kaken's explanation of the test says that after the test piece has been in the oven, colour change and staining (colour transfer) are graded with the grey scale (a reference scale for judging the degree of change in steps).^[3]

Evidence for this paragraph (3)

[1]

thermal migration (of disperse dye) ・causesDefines migration as disperse dye, not bonded to the fibre, moving over the fibre surface, which can transfer colour onto a light-coloured pigment print or reduce dry rubbing fastness. Cites a case where a white pigment print on a dark polyester shirt turned pink while in stock.contextual

1 source: 第53回：ケーススタディ⑨色の変化～汚染・色泣き～（アパレル散歩道） · full evidence

[2]

thermal migration (of disperse dye) ・propertyStates countermeasures: an appropriate test method (JIS L 0854 sublimation fastness, typically 120°C x 80 min, though some companies use 70°C x 48h or 130°C x 90min, and a matching fabric swatch may be used as the attached cloth); an appropriate quality standard (items below it improved via reduction-clearing, RC); and using thin interleaving paper (anti-sublimation paper) when packing, ideally specified in the sewing spec sheet. Also notes synthetic leather has high affinity for disperse dye and high staining risk, contact with moisture-wicking/quick-dry finished items can also promote staining, and that tape sewn onto white polyester fabric should be nylon rather than polyester.contextual

1 source: 第53回：ケーススタディ⑨色の変化～汚染・色泣き～（アパレル散歩道） · full evidence

[3]

disperse dye ・propertyDescribes the sublimation-fastness test (JIS L 0854) as sandwiching a composite specimen (attached with two adjacent fabrics, the second of which is polyester) between stainless-steel plates under load, placing it in a 120°C oven for 80 minutes, letting it cool without touching the adjacent fabrics, then grading colour change and staining with a grey scale; states its purpose is to evaluate colour transfer (migration) in materials such as polyester and acetate that use disperse dyes.contextual

Scope: Sublimation fastness test (JIS L 0854)

Source: 昇華堅ろう度試験（JIS L 0854） ・「昇華堅ろう度試験（JIS L 0854）」概要・目的・試験方法の各項 ・standard definition ・ checked against the source by AI

On the side where it is used deliberately, the same tendency to sublimate is thought to be what sublimation-transfer printing (a way of decorating cloth by transferring sublimated dye to it) relies on. Akaya of Nippon Kayaku explains that inkjet printing with disperse dyes (one way of applying dye to cloth to match a pattern) can be classified by fixation method (the way the dye is fixed to the fibre) into three: direct printing (wet-heat fixation), sublimation-transfer printing (dry-heat fixation) and direct printing (dry-heat fixation, or direct sublimation).^[1]

Evidence for this paragraph (1)

[1]

disperse dye ・propertyInkjet textile printing with disperse dye is described as classifiable into three fixation methods: direct printing (wet-heat fixing), sublimation-transfer printing (dry-heat fixing), and direct printing by dry-heat fixing (i.e. direct sublimation).contextual

Scope: inkjet textile printing with disperse dye

Source: 分散染料によるインクジェット捺染について （赤谷宜樹（日本化薬株式会社 機能化学品事業本部色素材料事業部）, 2015） ・3．分散染料によるインクジェット捺染方法 ・textbook ・ checked against the source by AI

Shirota of Canon Inc. says that disperse dye diffuses into the gaps in the amorphous regions of polyester fibre (parts where the molecules are not neatly aligned) and takes hold there. Because the gaps are very small, steam or a heat press is needed to open up the molecular chains and let dye molecules in.^[1] Shirota also says that in the direct printing (wet-heat fixation) method, it is essential to apply to polyester, which does not hold water well, a pretreatment agent that does hold water.^[2]

Evidence for this paragraph (2)

[1]

disperse dye ・mechanismDisperse dye is said to colour polyester by dye molecules diffusing into the fibre through gaps in its amorphous regions; because these gaps are very small, steaming (for direct disperse dye) or heat-pressing (for sublimation disperse dye) is needed to open the fibre's molecular chains enough for dye molecules to enter. Phthalocyanine- and xanthene-type skeletons are said not to be used as disperse dyes because their large molecular structures cannot diffuse within the chains.contextual

Scope: disperse dye and polyester fibre

Source: デジタルテキスタイル用色材 （城田衣（キヤノン株式会社 総合R&D本部）, 2015） ・4.2 分散染料 ・textbook ・ checked against the source by AI

[2]

disperse dye ・requiresBecause polyester has poor water-retention, when disperse ink is printed by the direct (wet-heat-fixed) method, applying a pretreatment agent with water-retaining properties to the fabric is described as essential.contextual

Scope: disperse ink under the direct/wet-heat-fixed printing method

Source: デジタルテキスタイル用色材 （城田衣（キヤノン株式会社 総合R&D本部）, 2015） ・4.1 プリント工程 ・textbook ・ checked against the source by AI

The Jacquard Products product page says that iDye Poly can also be used for sublimation-transfer work.^[1] The same property that is reported as an accident when dye migrates is also used as a technique on purpose. This site's reading is that these are two sides of the same phenomenon, sublimation.

Evidence for this paragraph (1)

[1]

iDye Poly ・used inStates that for blended fabrics, using iDye for Natural Fabrics together with the corresponding iDye Poly colour in the same dye bath colours both fibre types at once. Also mentions two further uses: sublimation-transfer work, and colouring the polyester thread that store-bought clothing is often sewn with.contextual

Scope: Applications and use of iDye Poly

Source: iDye Poly（商品ページ） （Jacquard Products） ・商品ページ「カラー一覧」欄外の注記 ・manufacturer statement ・ checked against the source by AI

The explanation so far holds under the following conditions. First, the fibres Imada gives as the target of disperse dyes are hydrophobic ones such as acetate and polyester, and the fibres Kaken lists are polyester, acetate, nylon, acrylic and the like. The dyes used for cotton and linen belong to a different class.^[1][2] Second, the figures for industrial high-temperature dyeing are from Nippon Kayaku, and those for carrier dyeing are from Imada; they are not measured values from a home pot.^[3][4] Third, in the range this site has checked, iDye Poly is the only product whose maker's own material states that it is a disperse dye. We cannot say for certain that the two Miyako-zome products dye by the same mechanism.^[5][6] Fourth, the countermeasures against thermal migration (reduction clearing, interleaving paper) rest on what Kiyoshima set out from the standpoint of apparel quality control. Whether the same effect can be had at home has not been confirmed, either in the sources or by this site.^[7]

Evidence for this paragraph (7)

[1]

disperse dye works by dyeing from a dispersion of sparingly soluble dyecontextual

Source: 分散染料 （一般財団法人カケンテストセンター） ・本文1〜2文目 ・institutional summary ・ checked against the source by AI

Source: 染色技術者のための染料化学（その8）7. その他合成繊維用染料 7.1 分散染料 （今田邦彦, 2003） ・P181 §7.1 1) ・textbook ・ checked against the source by AI

[2]

disperse dye is applicable to polyestercontextual

Source: 分散染料 （一般財団法人カケンテストセンター） ・本文「…に染色可能」 ・institutional summary ・ checked against the source by AI

[3]

disperse dye ・requiresDescribes industrial high-temperature disperse dyeing as using a sealed, pressure-rated dyeing machine: a bath adjusted to a mildly acidic pH (about 4.5-5) is raised from around 60°C to 120-135°C (usually 130°C for regular-type polyester) over 30-60 minutes and held there for 30-90 minutes, typically about 60.contextual

Scope: Industrial high-temperature disperse dyeing of polyester

Source: カヤロン ポリエステル染料 染色技術解説 （日本化薬株式会社, 2002） ・3-2-5. 高温染色 ・manufacturer statement ・ checked against the source by AI

[4]

disperse dye requires Carrier dyeing methodcontextual

Scope: Carrier dyeing method for polyester

Source: 染色技術者のための染料化学（その8）7. その他合成繊維用染料 7.1 分散染料 （今田邦彦, 2003） ・P185 §7.6(1)② ・textbook ・ checked against the source by AI

[5]

iDye Poly is a type of disperse dyecontextual

Scope: Jacquard Products' own website Glossary page, entry "Disperse dye"

Source: Jacquard Products - Glossary （Jacquard Products (Rupert, Gibbon & Spider, Inc.)） ・Glossaryページ、D項目「Disperse dye」の定義文 ・manufacturer statement ・ checked against the source by AI

[6]

Polyester Dye ・requiresDescribes the product as a set of 20g powder dye (in a plastic container) and 20g colour-intensifying booster (in a film bag, with instructions), requiring heated dyeing at about 90°C with the booster added, and a heat-resistant container prepared. States it comes in 14 colours which can be mixed, and is an ECO dye free of designated hazardous chemicals. The product page text does not use the words 'disperse dye' and gives no dye class name (acid, direct, reactive and so on).contextual

Scope: Miyako-zome Polyester Dye product page (the seller's own guidance). The page gives no dye class name

Source: ポリエステルダイ（商品ページ） （桂屋ファイングッズ株式会社（みやこ染）） ・商品ページ本文 ・manufacturer statement ・ checked against the source by AI

Source: ポリエステルダイを使ったポリエステル100％素材の染め方を動画でご紹介 （桂屋ファイングッズ株式会社（みやこ染）, 2020） ・染色を始める前に確認すること・準備するもの ・manufacturer statement ・ checked against the source by AI

[7]

thermal migration (of disperse dye) ・propertyStates countermeasures: an appropriate test method (JIS L 0854 sublimation fastness, typically 120°C x 80 min, though some companies use 70°C x 48h or 130°C x 90min, and a matching fabric swatch may be used as the attached cloth); an appropriate quality standard (items below it improved via reduction-clearing, RC); and using thin interleaving paper (anti-sublimation paper) when packing, ideally specified in the sewing spec sheet. Also notes synthetic leather has high affinity for disperse dye and high staining risk, contact with moisture-wicking/quick-dry finished items can also promote staining, and that tape sewn onto white polyester fabric should be nylon rather than polyester.contextual

1 source: 第53回：ケーススタディ⑨色の変化～汚染・色泣き～（アパレル散歩道） · full evidence

The white stitching in the opening scene and the thinly dyed polyester lie on either side of the same boundary; that is this site's reading. Burch explains that polyester sewing thread needs a dedicated dye class, disperse dye.^[1] Nippon Kayaku says that in industry these disperse dyes are used in sealed, high-temperature dyeing machines.^[2] That a home pot differs from those conditions is, as noted above, this site's reading. The next time you look at a garment you own, compare the colour of the thread in the seams, the fibre composition on the care label, and whether the dye packaging uses the words "disperse dye". You may start to see where this boundary lies.

Evidence for this paragraph (2)

[1]

polyester is insoluble in disperse dyecontextual

Scope: Sewing thread in ready-made clothing

Source: Dyeing thread in pre-sewn clothing (How can I get the thread to dye, too?) （Paula E. Burch, 2006） ・「Polyester thread」の段落冒頭 ・practitioner's record ・ checked against the source by AI

[2]

disperse dye ・requiresDescribes industrial high-temperature disperse dyeing as using a sealed, pressure-rated dyeing machine: a bath adjusted to a mildly acidic pH (about 4.5-5) is raised from around 60°C to 120-135°C (usually 130°C for regular-type polyester) over 30-60 minutes and held there for 30-90 minutes, typically about 60.contextual

Scope: Industrial high-temperature disperse dyeing of polyester

Source: カヤロン ポリエステル染料 染色技術解説 （日本化薬株式会社, 2002） ・3-2-5. 高温染色 ・manufacturer statement ・ checked against the source by AI

Pigments are a different story: like disperse dyes they do not dissolve in water, but they are held on the cloth as particles by a resin. For those, see the theme Glued on.

• 🧪 Do home polyester dyes (Miyako-zome Polyester Dye, iDye Poly) actually dye by the disperse-dye mechanism?
• Can the reasons polyester does not take the dye at home be laid out and compared by conditions?
• 🧪 Without the colour-deepening accelerator, how deep a shade will Cooldye Hot dye polyester?
• Is the "colour-deepening accelerator" for Cooldye Hot and Polyester Dye the same kind of chemical, in function, as the industrial carrier?
• 🧪 After using a disperse dye at home, does an after-treatment close to reduction clearing (soaking in hot water, a reducing agent and alkali) visibly reduce colour transfer by sublimation?