Slow-dye

Brouillon de mon livre à paraître "Teintures végétales pour les curieuses et les flemmardes"

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12.8.14 Sels de Glauber

Selon les Américaines, pour éviter le bringeage des tissus de coton, on peut ajouter 1g de gros sel par litre, à défaut d’avoir sous la main des sels de Glauber, alias le sulfate de sodium (forme naturelle décahydratée du sulfate de sodium, merci wiki)..

Ce que j'appelle bringé: coton de récup, mordancé AA, bain de craie -> dans le bain de campêche, mais pas tourné/foulonné... ni prétrempé dans bain basique (oublié).

Comment ça marche? On va dire « qu’il pousse le colorant dans le tissu uniformément ».

Référence plus sérieuse via http://cduv.net/upload/2009ajc.pdf : Effect of salt concentration: Addition of electrolytes results in enhanced rateof exhaustion and decrease in diffusion. The efficiency of increase in order of exhaustion of dye bath is of order KCl < Na2SO4 < NaCl25. During the dyeing process sodium sulphate was used as exhausting agent and hence added at later stage ofdyeing from point of view of even dyeing and maximum exhaustion of the dyebath. Inorganic salts have two main functions one is improvement of dyestuff affinity and second is the acceleration of the dyestuff associates and lowering solubility.The sodium ion being present in Glauber's salt interacts with negative charge side of cotton fabric and neutralizes it. The fabric loses its proton of hydroxyl group and become negatively charged. As a result water becomes slightly more acidic. Thisnegative charged layer is produced on fabric and then is entered to attach the colouranton cotton fiber form the dye bath. When sodium ion neutralizes the negative chargeof fiber, it facilitates the approach of dye molecules to approach the fiber withi nrange of hydrogen bond already formed between the fiber and dye molecule. As a result maximum colour is attached to fiber. But as the salt concentration increased,the dye uptake by fiber was reduced. This was because of interaction of complex formation with fiber. This complex formed aggregate on the fiber and it not onlycauses unevenness but also dye uptake as shown in Fig. 4. Thus the optimized saltconcentration is 1 g/L because too high concentration of salt has given uneven samples and it has given maximum affinity for colourant to attach the fiber tha tresulted in uneven dyeing.

Lu sur un forum des sciences (colorants chimiques) : « ... le sel neutre augmente l'activité du colorant en solution, augmente la concentration en ions dans le bain et diminue la solubilité du colorant". et ainsi favorise son absorption par la fibre.

Selon http://www.turkeyredjournal.com/archives/V15_I2/DeSouza.html, effet dépend de la teinture. Pourquoi? « The effect of the glauber salts was dye dependent. The lac, madder and cutch were more even, but it had a negative effect on brazilwood. In some cases, it also altered the resultant hue and value.” Demander MG??

xxxRésultats de leurs tests d'ajout sels de Glauberxx : doser finement (max 1g/litre) car au-delà d'un certain seuil, la prise de couleur est réduite

  • pour 100g de tissu, 1,5litre de jus (le litre ci-dessus sera diminué par la cuisson, diluer d'eau)
  • ajouter 1,5g de sels de glauber
  • teindre 60°C pdt 1 heure, OK si monte à 80°C

extrait de leuchs:

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