Dyeing, a highly complicated and multifaceted chemical process can be described in many different ways, but in short, it is a way of permanently altering the physical colour as perceived by the human of any surface, from cotton or silk fabric to things like glass or wood. There are many processes included in the chemistry of dyeing which describe the interaction of various molecules that bond together and ultimately has the effect of changing colour of an object. In addition to the general dyeing process, the ways in which dyes react to fabrics and other various objects in various environments such as the presence of mordants and acids will also be explored. Dyeing, something that nearly everyone experiences and sees through werely wearing coloured clothing, seeing stained glass windows, using tinted glasses, and many more things of the like, is a process that occurs on the molecular level and it a rather complicated process. The process of dying itself is make possible by various elements as explained by Abrahart which says that dyes have colour because of the following: ability to absorb light within the visible spectrum of 400-700 nanometers, the presence of at least one chromophore (which is a colour bearing group), having a structure with both double and single bonds, and lastly, having the ability to show the resonance of electrons, which is crucial for organic compounds. 2 As Paula E. Burch states on her website and comprehensive blog about the science and chemistry of dye, many dyes (like the ones available at grocery stores) only act as staining and washes out progressively, unlike a dye of high quality that bonds to the molecules of the object used and is permanent. 1 If one observes various models of different dyes, it becomes evident that the shape of the molecule absorbs light depending on it, and this is what causes change in colour.
1 Where the chemical process known as dyeing comes into play is when the fabric used and the dye come into contact: both are made out of molecules, and if one puts them together nothing will happen, which is why at this stage it is necessary for both surfaces to have a slight positive and negative charge, as without the sharing of an electron, the bond will be weak and the fabric will not dye effectively. 1 This concept is even more prevalent in explorations such as the second project of the course which explored the effect of various natural dyes on fabric. The fabric that was used was Gildan 100% cotton, and the dyes used included turmeric, food colouring, and Rooibos Red tea. In particular, food colouring demonstrates Burch’s statements on the chemical process of dyeing the best, most likely due to the fact that food colouring is not a high quality dye.
During conduction of the experiment, food colouring (blue in particular) did not attach almost at all to the fabric and only left behind a very pale blue residue that would most likely wash out over a few washes. The green food colouring acts similarly, and so did the tea. This alludes to the fact that the bond between the cotton molecules and the dye molecules was most probably very weak and there was no sharing of electrons occuring in the chemical reaction. In conclusion, To continue, dyeing is not only the elementary chemistry described that is dyeing as a general process; there are many layers involved with dyeing and results can differ based on fabric used, the type of dye, and especially other factors like environment and secondary variables. Two of the variables that were studied and explored at length through an exploration of various dyes in various settings are using mordants as well as acidity to alter results of dyeing fabric.
Looking at the chemical process involved in dyeing fabrics, in order for there to be a sufficient reaction between the dye and the cellulose in cotton fabrics to actually dye the fabric, the pH balance should increase. 1 Referring to dyeing with various natural household dyes and using acids such as vinegar, one observation that was made was that in acids, dyes tend to not bond to the fabric as well and the colour results in a much more diluted colour, especially in the case of suing Turmeric, which is a very strong dye by itself which was highly impacted by the use of an acidic substance. Using this information, it is easy to infer that a lower pH balance (which is therefore more acidic) will create a weaker bond between the fabric and the dye, an that a high pH balance is needed to create a sufficient reaction between the two surfaces. Additionally, using mordants in a dyeing environment also impacts the final colour and the result of how the fabric and dye react with each other. First and foremost, a mordant is known as a substance that is typically not organic that has the purpose of combining with a dye or a stain to secure it to a specific material.
3 From a perspective taking into considering the chemical process of dyeing, this should mean that mordants help dyes bond to a fabric and will increase the hue/saturation of the dye. On a molecular level, the attachment of mordants to dyes is made by coordinate and covalent bonds, a process also known as chelation, which is quite common. From a chemical perspective, a mordant can be described as stated by John R. Baker as “a polyvalent metal ion which forms coordination complexes with certain dyes”. 4 This coordination complex is commonly referred to as a lake. 4 The way that the mordant attaches to a fabric or tissue is fundamentally very similar to the process through which the mordant attaches to the dye, being chelation and the formation of covalent and coordinate bonds.
4 This chemical process is not visible in experimental results, as observations made inferred that the mordant used does not change the hue, but just decreases its saturation and intensity. However, the process described here states that the bond is strengthened, but does not state anything about the strength of the colour change perceived. Because natural dyes are weak on their own, a mordant is always necessary in order to secure the bond, and since there is a reaction occurring between the mordant, cotton, and the dye, the mordant does not serve as a source of colour, but has the ability to change the hue colour with the same dye. 5 When done correctly, it is observed that mordanting a fabric results in a fast and drastic change in colour, and can be explained by the molecular process where the metal atom from the mordant is incorporated into the lone electron from the dye, and then because metals have low energies, the overall energy is lowered, resulting in a colour change. 5 Overall, the incorporation of acids as well as various mordants to the complicated process of dyeing fabric directly relates to changes in colour, both resulting in more intense and more saturated hues, as well as much more diluted dyeing jobs cause by weak bonds. Ultimately, through exploration of various dyes under many different environments and variables, including the use of mordants and acids, the process of dyeing has clearly been exposed as a complex process which can be described using many different processes on a chemical and molecular level.
Using items such as turmeric, food colouring, and Rooibos Red tea has further expressed this idea and given depth to scientific concepts to describe and back up the process and science of dyeing.
