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Browsing by Subject "puuvilla"

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  • Puuvillan indigovärjäys morsingolla (Isatis tinctoria) : morsinkolajikkeen, uuttomenetelmän ja pelkistimen vaikutus värjäystulokseen ja värinkestoon 
    Niinimäki, Niina (2020)
    Indigo is one of humanity’s most important sources of blue color. Synthetic indigo is produced from oil refining by-products and uses chemicals that are harmful to the environment. Natural indigo would be more environmentally friendly, but it does not guarantee an environmentally friendly dyeing process, since sodium dithionite, which is environmentally harmful, is often used to reduce indigo. This study examines the dyeing of cotton with woad (Isatis tinctoria) and the reduction of indigo with environmentally friendly sugars. The goal is to find an environmentally friendly dyeing method suitable for home dyers and craft teaching. Indigo precursors were extracted from three different strains of woad by three slightly different steeping methods. Indigo was reduced to its water-soluble form with fructose and glucose, and control samples with sodium dithionite. The resulting indigo dye was used to dye cotton fabric. The color yield is considered in relation to the different strains of woad, extraction methods and reducing agents. In addition, the washing and abrasion resistance of the color with different strains of woad, extraction methods and reducing agents is examined. Longer extraction time and chopping of the leaves improved the dyeing result. However, in addition to indigo, chopped leaves and longer extraction time also resulted in increased amount of other colorants in the dye, as the samples were greener and more yellow than their controls. However, in laundering, these samples faded less than others and their color turned bluer as the yellow colorants washed away. Among the strains, the best color yield was obtained from the 2002 row spacing and seed quantity test conducted by the MTT Agrifood Research Finland (now known as the Natural Resources Institute Finland). There were no differences in the laundering and abrasion resistance tests between the woad strains. Indigo was successfully reduced with both fructose and glucose, but color yields were lighter and less blue than with sodium dithionite. There were no significant differences in color yield between fructose and glucose. Fructose scored slightly better than other reducing agents in laundering tests. Sugar reduction is thus well suited for both home dyeing and craft teaching, but to improve the coloring result, the woad leaves should be chopped and extracted in hot water (80 ˚C) for half an hour.
  • Selluloosakuitujen painovärjäys luonnonväreillä : puretus- ja apuaineiden vaikutus verihelttaseitikillä ja sipulilla painettujen kankaiden värinkestoon 
    Kylmälahti, Lotta (2014)
    The aim of the study was to deepen the knowledge of the possibilities of using natural dyes for printing of cellulose fibres. There has been little research on the topic and in these studies colour fastnesses have not reached the same level as with protein fibres. However, recent international studies provide encouraging results of dyeing cellulose fibres with natural dyes. Based on this research the aim was to develop an optimum printing paste recipe for cellulose fibres. The study compares how different mordants and auxiliaries affect the colour fastness of cotton and linen printed with Cortinarius semisanguineus and onion. The study also compares differences between pre-mordanting and in-paste mordanting. The experimental part of the study consisted of making the printing pastes, the pretreatments, printing and post-treatments of the fabrics and colour fastness testing. There were ten different types of printing paste recipes which were carried out with both dye materials. The mordants used were alum and tannin. The printing pastes were made acid with acetic acid or alkaline with soda ash. Pastes without any auxiliaries were also made. The thickening agent used in all of the pastes was Gum Tragacanth. The colour fastnesses of printed fabrics were tested to laundering, daylight and rubbing. The results showed that it is possible to achieve good washability and abrasion resistance properties when printing on cotton and linen with natural dyes. The test samples' fastness to light seemed quite weak though. The best fastness to laundering belonged to samples which were mordanted with tannin. It was notable however, that the Cortinarius semisanguineus gave best washing fastness results in acidic printing pastes as onion gave the best result in alkaline paste. There were no significant differences between the fastnesses of the pre-mordanted and in-paste mordanted samples.

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