compoundunder review
soda ash (sodium carbonate)
Also known as: soda ash, sodium carbonate, sal soda, Soda Ash Fixer
Sodium carbonate; an alkali used to raise pH in dyeing with fibre reactive dyes.
Pillar: Bonding
Claims and evidence (22)
colour splitting is attributed to soda ash (sodium carbonate)contextual
Scope: Ice dyeing; as explained by Dharma
Says some colours strike, or become permanent, faster in the presence of soda ash, so slower-striking colours travel more.
Limitations: 染料の販売会社自身の解説。独立した研究で確かめたものではない。公開日は頁内で確認できず。どの色が速いかは書かれていない。
Source: Did You Know... Fiber Reactive Dye - Pure Colors vs Mixed （Dharma Trading Co.） ・同上 ・manufacturer statement ・ checked against the source by AI
Dharma Fiber Reactive Procion dyes requires soda ash (sodium carbonate)contextual
The product description states at the outset that Soda Ash Fixer is required for use.
Limitations: 染料の販売会社自身の商品頁。当初は要約ツール経由で needs_verification としていたが、2026-09-23 に統合担当（Fable）が原文 HTML を取り直して該当文を確認した。
Source: Dharma Fiber Reactive Procion Dyes (product page) （Dharma Trading Co.） ・商品説明の冒頭、「Soda Ash Fixer is required for use」の文 ・manufacturer statement ・ checked against the source by AI
soda ash (sodium carbonate) is a type of sodium carbonate (Na2CO3); a mild alkali, more basic than baking soda (sodium bicarbonate)contextual
Describes soda ash as sodium carbonate (Na2CO3), a mild alkali that is more basic than baking soda (NaHCO3) and the active ingredient in washing soda.
Limitations: 個人の手染め解説サイト（最終更新 2015-01-22 と表示）。出典の記載は無い。
Source: What is soda ash, and what's it for in dyeing? （Paula E. Burch, 2015） ・冒頭と "Soda ash is the active ingredient..." の段落 ・practitioner's record ・ checked against the source by AI
soda ash (sodium carbonate) works by pHcontextual
Scope: Fibre reactive dye on cellulose fibre
Says the purpose of soda ash is simply to increase pH: it changes the pH so the dye reacts with the fibre, making a permanent connection, and "activates the fiber molecules so that they can chemically attack the dye".
Limitations: 個人の手染め解説サイト（最終更新 2015-01-22 と表示）。出典の記載は無い。
Source: What is soda ash, and what's it for in dyeing? （Paula E. Burch, 2015） ・"What is soda ash used for?" ・practitioner's record ・ checked against the source by AI
Says adding dissolved soda ash raises the pH of the dyebath, which enables the dye molecules to react chemically with the fibre molecules and fix.
Limitations: 染料の販売会社自身の説明。独立した研究で確かめたものではない。公開日は頁内で確認できず。
Source: Dharma's Fiber Reactive MX Dyes FAQ （Dharma Trading Co.） ・浸染の説明の段落、および "What is Soda Ash..." の回答 ・manufacturer statement ・ checked against the source by AI
Limits: Says the pre-soak raises the pH of the fabric to about 10.5; the text goes on to say this "raises the level of negative hydrogen ions" used in the bonding reaction.
Limitations: 染料の販売会社自身の説明。独立した研究で確かめたものではない。公開日は頁内で確認できず。「negative hydrogen ions」は化学の語として不正確に見える（水酸化物イオンのことか）。この部分は根拠にしない。lead を参照。
Source: Tie-Dye Instructions （Dharma Trading Co.） ・化学の説明の段落（"pre-soak raises the pH level..."） ・manufacturer statement ・ checked against the source by AI
States that although the type of alkali does not matter in principle, adding about 10-20 g/l of soda ash tends to give the optimum dyeing pH of around 11.5, which is why soda ash is often recommended.
Limitations: 学会誌の解説記事（講義欄）で、著者自身の実験ではなく引用文献に基づく整理。引用元原論文までは遡っていない。 中温染色タイプでの数値。低温・高温染色タイプでの最適pHの具体値は書かれていない。
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） ・P122 §2.5(1) ・textbook ・ checked against the source by AI
soda ash (sodium carbonate) is used in can be added before the dye, with the dye, or afterwards; adding it before is usual for tie-dyecontextual
Scope: Procion MX and similar fibre reactive dyes
Says there are three choices—before, with, or after the dye—with before being usual for tie-dye, and that soda ash stays in the fabric even if line-dried.
Limitations: 個人の手染め解説サイト（最終更新 2015-01-22 と表示）。出典の記載は無い。
Source: What is soda ash, and what's it for in dyeing? （Paula E. Burch, 2015） ・"How do you use soda ash with Procion MX..." ・practitioner's record ・ checked against the source by AI
baking soda (sodium bicarbonate) differs from soda ash (sodium carbonate)contextual
Warns against suppliers selling sodium bicarbonate instead: it is much less basic and will not work for most dyeing recipes.
Limitations: 個人の手染め解説サイト（最終更新 2015-01-22 と表示）。出典の記載は無い。
Source: What is soda ash, and what's it for in dyeing? （Paula E. Burch, 2015） ・"Where can you buy soda ash?" の末尾 ・practitioner's record ・ checked against the source by AI
Limits: Says vinegar or baking soda can substitute for soda ash on silk, but they require heat for vat dyeing and steam setting for direct application.
Limitations: 染料の販売会社自身の説明。独立した研究で確かめたものではない。公開日は頁内で確認できず。対象は絹。綿についての記述ではない。
Source: Dharma's Fiber Reactive MX Dyes FAQ （Dharma Trading Co.） ・絹についての回答 ・manufacturer statement ・ checked against the source by AI
Limits: Mentions that some tie-dyers have had success using baking soda and microwaving.
Limitations: 染料の販売会社自身の説明。独立した研究で確かめたものではない。公開日は頁内で確認できず。条件や結果の詳細は書かれていない。
Source: Tie-Dye Instructions （Dharma Trading Co.） ・化学の説明の段落 ・manufacturer statement ・ checked against the source by AI
washing soda (hydrated sodium carbonate) differs from soda ash (sodium carbonate)contextual
Says washing soda is a decahydrate so much more is needed—2.7 times by weight or 4.6 times by volume in theory.
Limitations: 個人の手染め解説サイト（最終更新 2015-01-22 と表示）。出典の記載は無い。
Source: What is soda ash, and what's it for in dyeing? （Paula E. Burch, 2015） ・"Hydration" ・practitioner's record ・ checked against the source by AI
soda ash (sodium carbonate) has the property of stored for years in humid conditions it absorbs water and appears to lose strength, but has merely bulked up and needs larger volumescontextual
Says anhydrous sodium carbonate stored for several years in humid conditions absorbs water and appears to lose strength when it has merely bulked up.
Limitations: 個人の手染め解説サイト（最終更新 2015-01-22 と表示）。出典の記載は無い。
Source: What is soda ash, and what's it for in dyeing? （Paula E. Burch, 2015） ・"Hydration" ・practitioner's record ・ checked against the source by AI
soda ash (sodium carbonate) is applicable to silkcontextual
Scope: Accounts of wool differ by source (Dharma's soda ash product page recommends acid dye instead, while the tie-dye instructions page says wool can be soda-ash dyed with half the amount and a 4-6 hour cure limit)
Says it can also be used with silk but not other protein fibres such as wool.
Limitations: 個人の手染め解説サイト（最終更新 2015-01-22 と表示）。出典の記載は無い。
Source: What is soda ash, and what's it for in dyeing? （Paula E. Burch, 2015） ・"What is soda ash used for?" ・practitioner's record ・ checked against the source by AI
Says soda ash can fix fibre reactive dyes on silk when heat-setting is not an option, with caution: presoak just before dyeing and cure only 4–6 hours; wool tends to feel brittle, so acid dyes with heat are better.
Limitations: 染料の販売会社自身の説明。独立した研究で確かめたものではない。公開日は頁内で確認できず。
Source: Soda Ash Fixer (product page) （Dharma Trading Co.） ・絹・毛についての注意 ・manufacturer statement ・ checked against the source by AI
Says soda ash is very hard on silk and wool: use half as much and cure no more than 4–6 hours, or use the vinegar/microwave method instead.
Limitations: 染料の販売会社自身の説明。独立した研究で確かめたものではない。公開日は頁内で確認できず。
Source: Tie-Dye Instructions （Dharma Trading Co.） ・絹・毛のタイダイの段落 ・manufacturer statement ・ checked against the source by AI
soda ash (sodium carbonate) has the property of sold with the description "a mild alkali used in many ways for dyeing"contextual
Scope: Aikuma's product description (given in both Japanese and English)
The product page describes it, in both Japanese and English, as "a mild alkali powder that is used in many ways for dyeing".
Limitations: この頁では反応染料に限定した説明はなく、「藍染めの助剤」カテゴリに分類されている。
Source: ソーダ灰（炭酸ソーダ）500g（商品頁） （藍熊染料株式会社） ・商品説明欄 ・manufacturer statement ・ checked against the source by AI
fixer (PAC FABRIC DYE kit) is a type of soda ash (sodium carbonate)contextual
The single-item fixer (50g) product description explicitly states "ingredient: sodium carbonate".
Source: 商品案内 （PAC FABRIC DYE） ・「PAC FABRIC DYE 固着剤」単品の商品説明 ・manufacturer statement ・ checked against the source by AI
post-dyeing colour-fixing agent differs from soda ash (sodium carbonate)contextual
Scope: Product line-ups and instructions of Tanaka Nao, Katsuraya Fine Goods, Mimura Senryo and PAC FABRIC DYE; not a claim about Japanese dye shops in general
Context: Tanaka Nao sells "Fixer 2" as a multi-purpose alkali fixer for its Reac dyes, giving the sequence dye → dry → apply Fixer 2 → leave → rinse → hot rinse → dry for non-immersion methods, and for room-temperature immersion dyeing, dyeing with anhydrous Glauber's salt and then adding Fixer 2.
Limitations: 色止め剤との区別は、この頁だけからは言えない。
Source: フィキサー2（商品頁） （田中直染料店） ・商品全体の構成（フィキサー2 vs ソーダ灰の別商品） ・manufacturer statement ・ checked against the source by AI
Katsuraya presents "Mikanol" as a product used only after dyeing, distinct from the dyes and auxiliaries used in dyeing itself.
Source: 色止剤 ミカノール 使い方説明書 （桂屋ファイングッズ株式会社） ・商品全体の構成（色止剤ミカノールの位置づけ） ・manufacturer statement ・ checked against the source by AI
Mimura groups Remafix and Sunclean Z, used after (not during) dyeing, under a heading for "post-dye treatment".
Source: 染色助剤 （ミムラセンリョウ株式会社） ・「染色後処理」の見出しとレマフイックス・サンクリンＺの位置づけ ・manufacturer statement ・ checked against the source by AI
PAC FABRIC DYE's instructions clearly separate the "fixer" used during dyeing (mixed into the dye solution) from the "colour-fix agent" used after dyeing (dissolved in separate water, into which the dyed item is soaked), as distinct steps.
Source: 使い方（基本の染め方・タイダイの染め方） （PAC FABRIC DYE） ・手順の順序（固着液の工程と色止め液の工程が別） ・manufacturer statement ・ checked against the source by AI
soda ash (sodium carbonate) is used in states that for Turquoise Blue G, Blue B and Green 6B, adding 10g of soda ash per litre of dye solution increases the depth of colour fixed, but lowers the stability of the dye solutioncontextual
Scope: Remazol dyes sold by Mimura Senryo, these three colours specifically
For Turquoise Blue G, Blue B and Green 6B, states that adding 10g of soda ash per litre of dye solution raises the depth of colour fixed, but lowers the stability of the dye solution.
Source: レマゾール染料 （ミムラセンリョウ株式会社） ・「◆染料の溶解」の段落末尾、3つ目の※注記 ・manufacturer statement ・ checked against the source by AI
soda ash (sodium carbonate) is used in describes it as a mild alkali used for a range of purposes, including scouring silk thread and neutralising acidcontextual
Scope: Tanaka Nao's granular soda ash product page
Describes it as a mild alkali with broad uses, including scouring silk thread and neutralising acid.
Limitations: 化学式・純度・濃度など成分の記載は無い。
Source: ソーダ灰〈顆粒〉（商品頁） （田中直染料店） ・商品説明欄冒頭 ・manufacturer statement ・ checked against the source by AI
soda ash (sodium carbonate) has the property of states that when dissolving it in water or a dye solution, it should be stirred in graduallycontextual
Scope: Tanaka Nao's granular soda ash product page
Advises stirring the liquid while adding it gradually, when dissolving soda ash in water or a dye solution.
Limitations: 分量の目安（g/l等）は示されていない。
Source: ソーダ灰〈顆粒〉（商品頁） （田中直染料店） ・商品説明欄、使用方法の一文 ・manufacturer statement ・ checked against the source by AI
Dharma Dye Fixative differs from soda ash (sodium carbonate)contextual
States it does not replace an ordinary fixative such as soda ash; rather, it is applied once the dyeing step itself is finished.
Source: Dharma Dye Fixative (product page, Description + Instructions tabs) （Dharma Trading Co.） ・「GENERAL INFORMATION AND USE」の項 ・manufacturer statement ・ checked against the source by AI
reactive dye requires soda ash (sodium carbonate)contextual
Scope: as described for home-studio batik in the US using Procion MX dye
this practitioner states soda ash fixes Procion dye in room-temperature water, with no need for hot water that would melt the wax
Limitations: 米国の家庭向けバティックについての記述
Source: How to Batik （Paula E. Burch, 1999） ・"Materials for making batik" リスト内 "Soda Ash Dye Fixer"の項 ・practitioner's record ・ checked against the source by AI
soda ash (sodium carbonate) causes States that minerals in hard water combine with sodium carbonate (soda ash) to create "soap scum", which in the case of exceptionally hard water can cause problems such as spotting in dyeing.contextual
States hard-water minerals combine with soda ash to form "soap scum", which in exceptionally hard water can cause problems such as spotting during dyeing.
Source: Dyeing with hard water: water softeners, distilled water, and spring water （Paula E. Burch, 2007） ・冒頭段落 ・practitioner's record ・ checked against the source by AI
soda ash (sodium carbonate) has the property of The government model SDS for soda ash (sodium carbonate, 100% concentration) reports skin corrosion/irritation as “not classified,” but serious eye damage/eye irritation as “Category 1” and acute toxicity by dust inhalation as “Category 4,” with the signal word “Danger” and hazard statements including “harmful if inhaled,” “causes serious eye damage,” and “may cause respiratory irritation.”contextual
Scope: Soda ash (sodium carbonate) itself, as a 100%-concentration substance
Classifies skin corrosion/irritation as not classified, serious eye damage/eye irritation as Category 1, and acute inhalation (dust) toxicity as Category 4, with signal word “Danger” and hazard statements including “harmful if inhaled,” “serious eye damage,” and possible respiratory irritation.
Source: 化学物質：炭酸ナトリウム（GHSモデルSDS情報） （厚生労働省, 2009） ・２．危険有害性の要約 ・standard definition ・ checked against the source by AI
soda ash (sodium carbonate) has the property of The basis given for classifying serious eye damage as Category 1 includes a rabbit test in which corneal, iridal and conjunctival symptoms appeared and persisted after 14 days, and another test in which corneal clouding persisted for 7 days; a 5% aqueous solution is reported to have a pH of 11.58-11.7.contextual
Cites a rabbit test in which unrinsed eyes showed corneal, iridal and conjunctival symptoms still present at the end of a 14-day observation, and another test with corneal clouding persisting 7 days; gives the pH of a 5% solution as 11.58 (the physical-properties section gives 11.7).
Limitations: pHの値が節によって11.58と11.7で異なるが、いずれも同じ資料内の記載。
Source: 化学物質：炭酸ナトリウム（GHSモデルSDS情報） （厚生労働省, 2009） ・１１．有害性情報／眼に対する重篤な損傷・刺激性 ・standard definition ・ checked against the source by AI
soda ash (sodium carbonate) has the property of The listed safety measures include avoiding inhalation of dust, vapour, fume or spray, using the product only outdoors or in a well-ventilated area, and wearing suitable eye and face protection; first-aid measures given include moving to fresh air if inhaled and rinsing the eyes with water for several minutes if it gets in the eyes.contextual
Lists avoiding inhalation, using the product outdoors or in a well-ventilated area, and wearing eye/face protection as safety measures, and moving to fresh air if inhaled and rinsing the eyes with water for several minutes as first aid.
Source: 化学物質：炭酸ナトリウム（GHSモデルSDS情報） （厚生労働省, 2009） ・２．危険有害性の要約／ラベル要素（注意書き）と４．応急措置 ・standard definition ・ checked against the source by AI
soda ash (sodium carbonate) has the property of Dharma Trading Co. states that molecules of dye and most chemicals are too large to be absorbed through the skin, but that chemicals such as soda ash are caustic and need to be handled with care.contextual
Explains that most dye and chemical molecules are simply too big to pass through the skin and get into the body, yet still flags certain chemicals, soda ash among them, as caustic substances that call for careful handling regardless.
Source: General SAFETY Information for Dyes & Chemicals （Dharma Trading Co.） ・General SAFETY Information for Dyes & Chemicals、ゴム手袋についての段落 ・manufacturer statement ・ checked against the source by AI
Open questions (1)
Does pre-soaking in soda ash give a different result from applying it afterwards?🧪 testable at home
That soda ash raises pH so reactive dye reacts with the fibre is now documented (Dharma, Burch). Burch lists three options—before, with, or after. The recorded home process soaks first and also adds soda ash after the dye and ice. Does the order change depth of shade or splitting?