 Hello and good morning to all. Welcome to another episode of Steamboat. For those who are joining us here for the first time, Steamboat is an outreach program organized by Homi Baba Center for Science Education. On every second Sunday of the month, we come with a new topic related to science, technology, engineering, arts and mathematics. So today's topic that we have is Indigo and its Blue Devolutions. And to talk to us about Indigo, we have with us Inrani Dasen. She works in the Chemistry Education Group at HBCSE. She works on the development and standardization of experiments for both undergraduate and school levels. Her interest specifically lies in the area of inorganic chemistry and she has an act for colorful inorganic compounds too. She has been guiding students, student projects in analytical and inorganic chemistry. So we start the session and I would like to tell you it is going to be interactive so please put down your answers and questions in the chat section. Our Zoom viewers can unmute and ask the questions. So with that I would request Inrani to start with the session. Thank you Vishal. So good morning to all of you. So today my, so I'm going to talk about one of the very nice areas which even and also one of the very nice color that's Indigo. And so I'm going to talk basically about history of Indigo as a tie, the different political interferences that it encountered, the revolutions that it caused, and the current scenario and whatever is the current production of it. So let me start. So can you tell me what comes to your mind when you think about Indigo? What comes to your mind when you think about Indigo? We have one rainbow with cure. Okay rainbow yeah. Anything else? Viewers you can put down in the chat on YouTube also. Line. One person. Line. Indigo Airlines. Indigo Airlines yeah. Okay so let me, what comes to my mind? There's one more, paint. Paint? Okay Indigo paint. So there are a few things which come to my mind also. So first thing I, whenever I talk about Indigo, the one which comes to my mind is this Indigo card by Tata. There is this beautiful blue color birds which are found in the Himalayan region, which are known as Brandelas. Ujjala blue, which we have seen very often and used in our home also for whitening our clothes. The blue kingpisher, which is very common. Of course you said Indigo Airlines and not to mention the list is rainbow. There are many other things which we can correlate but these are the common things which come to our mind when we talk about Indigo. So in all this we find that even if we are talking about it, something is just related to blue. You say something which is just related to blue, it's other colors or whatever it is but something that is related to blue. So is this Indigo, by the name which we call, is it different from blue? If it is blue only, how is it different? Is it light blue, dark blue? What exactly it is? Is it only color? What do you think? Is it different from blue? What kind of colors, color shades do you think it could be? Can I get some answers? We have a couple of answers. A little dark blue with violet or purple. Another answer we have is it is some dark blue. Dark blue, okay. Okay, so for us, is this the blue which we are talking about? The robin blue which we have used in our home. The blue in this flower which is a very common flower found all over is in Hindi or it's called as aprajita. The jeans blue, the bandh li blue or the blue color of the crows, a crow eggs or the blue color of this flower. So it's a water hyacinth which is also called as jal kumbhi. So we see that there's a variety of things, a variety of colors come to our mind when we talk about indigo, whether it is dark blue, light blue, whether it has a purple shade, dark purple shade, whatever. So let us then, what is indigo? Is it only a color? Only a color? Is it something which gives color to the fabric like ties, pens, color giving substances? Do we find it? Is it found naturally? Is it human made? Do we have to go on mining for rocks? Or does it have any plant origin? So today's session, we will try to explore these different aspects of indigo. So before we go briefly into the history, so one very interesting thing I would like to mention about indigo. So can anyone say who this person is? Okay, so anyway, so this person is Newton, which we know from a very, from a school days. And there's something related to him also, he performs certain light experiments. So what we see here, we see just a prism and white light is passing through the prism. And on the other side of the prism, the white light is getting separated into different colors. Yeah, so what does this have to do with indigo? What basically does Newton have to do with indigo? The separation of colors until Newton, the separation of colors, they were divided into six different colors. In the modern context, in the modern context, we say, like one of you said in very earlier slides, Vibgio, the rainbow, the Vibgio, whenever you say Vibgio, you find that there are seven colors. But until then, there were six base colors which were given. Newton introduced the color indigo, which was placed between violet and blue, sort of like a mixture of violet and blue. What are you going to talk about? Dark blue also, whatever. So the color indigo was introduced into the spectrum by Newton. So now let me come to some historical facts. So the archaeological site in Peru, that is in Boca Brita, people went after excavation, people found out certain sand, they found there were sample of clothes fabric which were dyed using this blue color. These were analyzed using modern methods. And after the analysis, these were found that the dye which was used to impart blue color to the cloth was indigo. Imagine that the 6000 BC, I mean roughly 8000 years before us. It didn't become slightly earlier. Even in the Indus Valley civilization, when it was excavated, there were four different seeds of indigo plants found in the Indus Valley. Along with the seeds, sample method of cloth was also found, which were dyed in blue color. So you see indigo as a substance, as a dye which is used to give color to the substance was from antiquity. I mean 8000, 10,000 years before people were using it. It's not a modern dye. It was being used. And in both these two cases, these were found to have plant origins. Obviously in Indus Valley civilization, people unearthed different varieties of indigo seeds. You see that it was known to people from very, very old times. So can anyone tell what is this picture about? Or can you relate this picture to any kind of civilization? We have encountered such kind of pictures in our history textbooks also, in our school days. So viewers, can any one of you... We have one answer, like looks like Egyptian type. Okay. Anything else? Yes. The answer is I think we shouldn't. Okay. Okay. Yeah, you're correct. It is a wall painting from an ancient Egyptian civilization, wall paintings of Egyptian civilization. It also has blue color. Can you see the blue color? But the color is not plant-based. The color after analysis of the color, it was found to be synthesized by humans. It had inorganic origins. So I'm not going to go into very detailed comparison, but basically it had some calcium, some copper and some silica. So it was made synthetically by these people. So this Egyptian blue color is often termed as first synthetic, not dye, but pigment. Pigment is a modern time term, but there's a difference between dye and pigment. Dye generally have, often have sources from plant origins or they are often carbon-based compounds, where pigments generally have inorganic origins and generally they are synthetically made to pair in the lab industry. Another simulation. This is another simulation. Can any one of you tell what is the simulation or have you seen it somewhere? So do we have any guesses for this? Okay. We have one, something inquired to know. Yeah. Okay. So this is a painting from the Maya civilization. So Maya civilization flourished from 8000 BC to 1680 and roughly like 10,000 years in the region of now present Mexico, the southern Mexico Honduras El Salvador. So the Central American part Maya civilization had flourished for so for around quite a long time. And for them also the blue color was a very important color in their lives. They had also, they also had the blue color which we see here has both plant origin as well as like inorganic origin when I say it's natural. It was a mixture of plant-based origin and natural clay. So we see on one hand Egyptians, Egyptian civilization is also using the blue color. For them blue color was a symbol of wealth. Whereas in Maya civilization we find the for them the blue color was a symbol of different sacrifices, different rituals. So blue color was used across different kind of civilization at different times. And it's a very common color and a very well revert color I should say. So this is also a world heritage site and it is in China. So can you tell, can anyone tell what it is? I would like to take a guess. Okay. Yeah, I was going to guess something similar looks like small statues we have in the comment. Okay, yeah statues here. Anything else? So these are. Yeah, I would like to take a look like terracotta. Is it something similar to that? Yeah, it is something similar. It is something similar. Yeah, but yeah. So you are correct. You are correct. And also the person who answered is also these are sculptures. So these are the Chinese terracotta army sculptures. And these sculptures have been painted using the blue color in this culture, which is not very evident here now. But the ones they were excavated the blue color was there. But as soon as it got exposed to it, the lot of blue color just, you know, it got removed. So the color blue which was used here again was synthetically prepared. Now this is from roughly 200 BC or something around when BC, when he was the king. So he was the first emperor of China, Queen Shihang. And people during that time believed that if the army, if the, you know, the sculptures were made and they were buried with him. So the army would protect him in his afterlife. So that was a belief there. So that was the reason that the first emperor, you know, that had such a huge burial tomb, and it's like roughly 90 square kilometers. It's a huge area. And this is filled up with armies, armies depicting generals, different, different ranks of armies. So we see the color is not again plant based here. It's again has an artificial means it's again a synthetic one. Let us come back to India. So Indigo was also known. So we have seen that Indigo was known to different civilization, but Indigo was also known. We have seen India in the Salis civilization. It was also known. So people who actually exporting in Indigo to the Arab countries also the Middle East countries are Central Asia. So these were getting exported. How about the mention, clear, very clear mention about it was done by one of one of them previous they may be mentioned about Indigo in the previous literature also. But at least the one which is very prominent was given by this person. Can you tell who this person is? He was an Italian traveler who had traveled extensively to China and India and when he was in China and he spent a lot of time from there to India. So a few months he was there at least in India. So viewers, can you take a guess on this on YouTube. Okay. So he was Marco Polo. He was an Italian merchant and he Marco Polo had mentioned very clearly in his diary about the Indigo production in India. However, he had mentioned it that it was during that time. The Indigo production was in South Southern India, you know, mostly Southern India a few parts in the Western India. But he had talked about in detail how these were manufactured, how the whole process was done, and these were getting exported. So a little ahead of him, we have this person. So he's known for finding out the route to India, sea route to India from Europe. So can you tell who this person is? I believe this one should be easy, someone should guess, otherwise I would take a guess on that. I think this is Vasco da Gama. This is Vasco da Gama. Yes, we also have in the chat. Okay, yeah. Vasco da Gama. Yeah, he's Vasco da Gama. We know about Vasco da Gama also from my history books. So Vasco da Gama had found out the route and had already started importing Indigo to Europe. So prior to that Indigo was again have was already exported to the Middle East countries. But these were the people who are specifically, you know, like, like multiple specifically written about it, because Vasco da Gama was also doing it and it has been already written down. Coming to a more like, I said, we have this army, so I will not right now, let us go ahead. So this is the uniform of the French army. Basically, it's a painting, but the painting of the French army. And these are the blue uniforms, and these blue uniforms had the color blue was from two sources now, both a plant base, but two sources. One was the vote plant, and the other was the Indigo plant. So what are these two sources will come to it later, but let us for now understand that they are two sources, two plant sources of the Indigo. And what kind of, you know, political pressures these the competition and the political pressures it caused. So here we are here now so let us see now. So during that time, you know, like 15th or 16th century, the Ujjain was one of the places known for manufacture Indigo from Indigo plant. It was exported to Middle East Europe. Surat was a very huge port. So the Indigo was, you know, both through the Silk route as well as to the Sea route Indigo was getting exported. It was so it was such a in high demand and it was also such very duties very high profits people used to use it as a currency for the daily expenses also when people travel for the daily expenses also people used it for as a currency. And of course for its high profit, it was also a luxury item. So, because of all this, it was termed as blue gold, because it was such in demand, it was price was extremely high, it was not easy to find India or India Philippines and I mean basically South Eastern countries for the only place where you will, where it was getting manufactured. This Indigo, you had another source, but there was also competition. So it was called as blue gold. Strips of Indigo diet cloth were also used in African trade unit was in the 15th century. So we see Indigo was used both as a currency and it was such a luxury item it was called as very blue gold. However, the European source of the blue dye was the wool plant, which we just discussed. So import of Indigo from India to Europe. Obviously it devastated the local trade. Certain in some countries like England, France and Germany, they were that penalties also given in some cases restrictions were already in place and that penalties in certain cases were also given. So the other way is that in Central America, they were competition between the Spanish merchants and the Dutch in this Portuguese merchants pain imported Indigo from Guatemala where others were importing Indigo from India. So the Indigo, which was a very high demand was coming majorly from India. So the first revolution, so the apart from the debt penalty and everything, the first the revelation which it caused was due to the blue color of the denim or the jeans. So denim is also very sturdy cotton cloth, which has its origin in France, whereas jeans, which is also cotton, but often it is also blended with wool also had its origin in Italy. So both of them were using both these thoughts were getting used by the working class men sellers minus basically the working class people. So both of them were using the Indigo and the Indigo was maximum of the Indigo was coming from India. Of course, the Indigo which was produced in Europe also from the vote plan was also getting used. However, Indigo which was produced from the vote plan was not very intense as that which was getting exported from India. So the demand of Indigo from India had risen very high. We know Levy straws, we know Levy jeans that's very known to us, very common. So Louis, who later changed his name to Levy straws. So Levy straws, he was a German person who went to New York and they were already you know they were into this business of producing jeans and I mean denim denim. They were producing that they were cloth merchants were factories in New York also. And so he and Jacob Davis, Jacob Davis was a tailor who was working with Levy straws. They popularized this riveted blue jeans. So this is very common now. This was not originally there when this denim was being used by this working class men. So what, why did they do it? In fact, the cloth was very steady. It was, you know, after several washing sessions, it was highly didn't get tear off. But the pressure area, the pressure points, like for example, the pockets, the corner of the pockets, those got torn up very easily due to regular use wear and tear. It was those got torn up very, very easily and very fast. So what did these people do they I mean use this small couple of copper based buttons and the corners of the pockets, they riveted it. And basically they use these buttons there so that you know the corners don't tear off. Once this was done, it, it become very, very popular now everything is there. You have a very sturdy jeans you have a jeans which is not very. I mean it doesn't tear off very easily and the color is quite fast compared. And you can use it for so long. And it was used by the working place so gene or blue denim or jeans basically that it was a symbol of youth durability hard work because it was used by the working people. It was rebellion. It was a fashion thing. It was in both it was in fashion so students were using it students were wearing it women were started wearing it. So and of course it all was also stood for protests so whenever there was a sort of protest specially in America, people used to wear jeans. So it has said so the jeans revolution was caused because partly a majority of it is because of the Indigo. Now let us come back to the Indian context. Indigo was grown in India. However, when it was grown in the 16th century to 17th century I mean it was in the western parts western India and very few area of your southern India. But basically it was in the western area like present day Gujarat, a few areas of Maharashtra, Madhya Pradesh and in parts of southern India. However, because of several twists and turns in the history and also the whole Indigo cultivation got shifted into your eastern India. Eastern India means then Bengal and as well as Bangladesh major full Bangladesh. So a lot of area in Bengal and Bangladesh, especially in southern Bengal and Bangladesh was Indigo was cultivated. The two ways it was cultivated was one was called as niche where the planters, these planters were often the landlords, Indian landlords or the people who are working for the British government. So these planters they purchased the land from the needy farmers and started the cultivation. So that is one way of the cultivation and the other way it was called as riot. So the planters they give advances to agricultural tenants agricultural tenants for farmers basically the farmers and certain quantity of Indigo will be cultivated on the holdings and sell and sell the produce to the planters. So whatever the farmer had purchased I mean was allowed to a certain portion of the land he will be using to cultivate Indigo. So it was called as a niche food crop but we had to do Indigo later on that become converted got mostly converted into mostly 100%. So it was causing a stir. So they were grudge and reported gross abuses in the riot system. The needy cultivators they took loans and loans at high interest. Often there was crop failure because of the droughts and the rains, which led to death that food crop was not allowed to grow in seasons you know so people were hungry. Whatever land holding I had a major of it had to be cultivated using Indigo I was not allowed to grow food I don't have food in my hands I'm hungry my family is hungry hungry. They were rivalry between the Indian landlords and the planters. So often the crops were seized from the farmers. So riots were actually reduced to partial slavery. You know you what but no pay will be given to you. So 1859 is what is the major one but things were slowly and slowly it was growing in the background. Along with partial resistance by passive resistance where people were trying to mitigate the issues through conversation or through meetings. There are also armed revolt by farmers who refused to show Indigo they attacked the planters and the machinery they burned on the Indigo Depot. So there was a huge revolution in during that time in Bengal and which led to the formation of the Indigo Commission in 1860. The effect was it was shifted from Bengal to southern India to be hard north and southern India where it was not clashing with the food crops. North is basically they are like they you they the staple food item is weak so it was it didn't clash with them. However, it did clash with the Bihar in Bihar and in some parts in southern India in Bihar it again led to the uprising in protest of growing Indigo for similar reasons which were had already happened in Bengal earlier. And by the time Gandhiji had also come back from England and the first Satya Braha was held in Champaran in Bihar and that is in 1917. So that was the first Satya Braha by Gandhiji because they didn't want to grow Indigo. So let us now come to some something related to the sources and some chemistry part of it. So natural sources of Indigo are these are the two major natural sources. One is coming from Indigo for a Tintoria which is called as Neil and is very often found out all over India and not only India in the Indian subcontinent actually. And the other source which is found in the temporary regions is Satish Tintoria which is called as a wood plant which we already heard that Europe was producing wood plants. So the tropical areas you have this Indigo for a Tintoria or the Neil whereas in the temperate areas you will have this wood plant. So these are the two major species. There are also some minor species which give you some color but the color intensity for which we obtain from Neil is very intense and it's also the amount is also quite high. So how is it extracted from the plant? So historically these are generally cultivated from April onwards. So you can understand from April onwards means pre-Khadi crop which is the major Khadi crop. So pre-Khadi crop is going to be problematic and they are often cut in July. So ancient times these plants were squeezed, the plants were beaten, squeezed, mixed in water, kept for many days. They were fermented there and the insoluble part which were deposited on the bottom that was taken out for dying. However modern methods, modern methods within the same modern methods not exactly now but like during the medieval times also. So it just there was slightly small difference. The leaves were cut, dried, loaded into the concrete batch which were filled with water, fermented. And the water was allowed to run to very small holes. When the water was allowed to run to the small holes the indigo which was deposited could not pass through the holes. So those were getting filtered off. So that indigo was taken out and used for further processing. So on the right hand side I have these pictures which are these are photographs taken in Allahabad in around 1877. So you can see it has already shifted now by 1877 already shifted to Northern India. So this is in Allahabad and these are the various stages of indigo plantation and it's harvesting. So the first one depicts the ripping then the cutting of the second one is your cutting of the leaves. The third one is where you put the leaves into the concrete batch and then you press them. Fourth is again you are whipping the leaves. After fermentation you are whipping the leaves and whatever is there is the pasty mass which has come out of them using your legs. The fifth one is here. After that the pasty mass is taken into the factories where they are made into slabs, big slabs. So these big blue slabs from where then and the last one is where you cut the slabs into small sizes and take it to the market for sale. So that was the extraction part. So how is the dyeing happening? The chief component of the indigo dye is indigotin. It's a chief component but indigo is also a mixture in fact. However the chief component is indigotin you have some other compounds also. During fermentation one of the chemicals which is present from the leaves and come into the solution which also has a sugar moiety here. That gets converted into this molecule which is called as indoxin. So this is indigant the sugar has removed and this is converted into indoxin from where it is converted into indigotin. Two molecules of indoxin and it gets oxidized and in fact it is getting converted to indigotin. So this extract is sent to the next fat and mechanically agitated to produce indigotin. You have to agitate it. That's a way of giving energy to it and that you are making these indoxin molecules combined with each other and there you get the indigotin. The indigotin after you separate it out since it's insoluble in water you separate it out make it into slabs and the slabs are sold in the market as cakes. So this is a cake of indigo cake which is sold in the market. However you can also get it in the powder form but how is the dyeing happening? We tend to know that indigo is insoluble in water. So how is the dyeing happening? How is it going to dye my clothes if it is insoluble in water? So what happens is that the indigotin or the slab which is taken is first converted into a soluble form in water. Using different chemicals it is converted into soluble form in water. Indigotin is blue in color. When it is getting solubilized in water because of certain chemical reactions it becomes greenish yellow in color. So the greenish yellow color has a you know this is a form in which you have the greenish yellow in color which is known as a lucoindigo. This is soluble in water. You dip the yarn or you dip your fabric there into the solution. Keep it for sometime depending on how intense the color you want it may be how intense. The intensity also depends on the concentration as well as the time you are keeping the cloth there. And then you remove it, you air dry it. So when you are dipping the cloth in this solution having lucoindigo the cloth is also not colored and it is like yellowish white very light yellowish white. However when you keep it in drying it turns blue. So what happens then? There we find that it has again converted into one on drying it gets converted into the Indigotin which is blue in color. You are understanding so it's such a nice in a simple very very simple one. You take the slab you just dip it in water you somehow you convert it into the soluble form using some chemicals which are readily available to it and you dip the cloth into it. The cloth turns the cloth is not colored however on drying you find the color has come back. The deep blue color of Indigo has already come back. From all this we come to we know and up till now we have seen that Indigo was in a very huge demand. I mean people were Europe, America, wherever it is. It was in huge demand but the problem was it is also hugely cumbersome process the extraction harvesting extraction and then you know and you know the producing the final cake was so laborious method time consuming method so people already started finding alternate routes, alternate routes to prepare Indigo. So there were a lot of research going on during that time in different countries how the one which we should mention here was by Adolf Von Beyer. So before I go about what he has done in Indigo just a small very very brief biography of Adolf Von Beyer. He had studied chemistry under Robert Wunson. So can you anyone tell who was this Robert Wunson anything comes to your mind when you hear about this word. The name Robert Wunson. We have in chat Wunson Werner. Great, very nice. Yeah, he was the person who had designed that Wunson Werner. So Adolf Von Beyer had worked with Robert Wunson and then he had also worked with August Kekeule. So can anyone tell? How can we relate Kekeule to anything in chemistry? Can we relate him to anything in chemistry? We have, yeah, benzene. Yes, the Kekeule gave us the famous structure of benzene. So we know both of them, right. So Beyer had worked with both these people and for a very long time he had worked with Kekeule. Kekeule was also along with him for various of his, you know, this different kind of areas in which he had worked. Von Beyer along with his team of course was credited with the synthesis of phenolphthalein, fluorescent, barbituric acid. So phenolphthalein was used as a dye dye and barbituric acid had had medicinal properties. So a lot of research was going on but he was credited. He and his team members were credited for preparing it synthetically in the labs. Then of course synthesis of indigo, strain theory of triple bonds and small carbon. So Beyer had contributed a lot to organic chemistry, a lot to organic chemistry and a basic understanding of chemistry also. As well as to the industry because he had prepared synthetically from his synthesis procedures which were later modified was these compounds were synthesized in the industrial scale. So he had done a lot for the industry as well as a lot for the organic chemistry specifically. So what did he do? He first, so Beyer said in his Nobel lecture he had told that, you know, I was very fascinated with this color blue. I just wanted to understand what is this color blue? I mean basically in indigo, he was talking about indigo. So he carried it forward. He first tried to describe, you know, he tried to determine the structure of indigo whatever the way they had in their means at the disposal. Using those means he found out the structure of indigo. He first determined the structure by degrading the indigo dye and found that the main component of the indigo dye was the indole molecule. So here we see the indole molecule, you know, this is my indole molecule. So we say it is a heterocyclic compound. So you have a benzene ring and you have also another pipeline ring, but with a nitrogen there. So these are called as heterocyclic compounds. So he found that it was an indole molecule. So when he found it out and after a lot of discussion among his members, they first tried to synthesize indigo from esatine. So this is my esatine molecule. So he synthesized esatine. Sorry, he synthesized indigo from esatine. Then also he tried it out from cinnamon acid and later on from orthonitrobenzaldehyde. All of these gave him not very good results, but what could be done in the laboratory scale. You saw not very high. The purity was often a problem. But indigo was synthesized all in all the three methods, but they were couldn't be taken to the large scale production. It's actually the industrial scale production because it was very difficult for them to get the starting compounds. Difficult in obtaining starting compounds because you also have to depend on the coal tar industry to get certain of the starting materials. So esatine and some of these were obtained from the petroleum industry, the products of the petroleum industry. So getting those were also becoming a problem. Then the synthesis procedure was also quite cumbersome and often the yields were like 10 percent, 20 percent. So those things could be taken into the large scale. So, however, because of so many achievements and because of so many contributions to chemistry, Bondare was awarded the 1905 Nobel Prize in Chemistry for its services in the advancement of chemistry as well as the industry. Then, similar time in Germany also, in Germany only, Carl Human was also working, trying to find out the methods of preparation of synthesis of indigo. So, after a lot of trials in the lab, he found out that this is the main molecule, N phenylglacin. This is the main molecule which he needs to prepare this indigo. He understood that when I, when he has this molecule, when I have this molecule, the next steps were becoming quite easy for him. So, but for preparing this molecule, he again had to depend on the petroleum industry also because for that he needed aniline or anthranilic acid to prepare this N phenylglacin. But he could preserve, but what he was said and done, Carl Human could prepare from aniline indigo which was of course low yield and from anthranilic acid he got indigo which was very high yield but it was very expensive. The whole group was very expensive. However, during that time also, see up till 1900, up till 1900, both based on the bond bear process as well as Carl Human process, industrial scale of production of indigo was already on the way. It was less, but it had to come into the market because the demand was extremely high. So people were taking it, you know, it was such an expensive thing. So people had already in minds about the profits. So one of the one of the chemical German chemical company that is BSF had already brought into the market during 1890s and they've already bought into the market with the slabs of indigo. I mean, the indigo cakes, they've already marketed it from the industrial scale. And that of course they were using Carl Human process. They didn't adopt a bear process because there were a lot of other trials. So there are a lot of history about it. I'm not going into history of it. So it was already there, but the yield was quite low. People were also looking for alternate methods. So in 1901, John S. Leger, who was working with Dirt and Degusa, which is now every he modified the humans method using sodium amide and had also had it patented. This sodium amide method using the sodium amide method was quite efficient. Eel was roughly around 90%. Purity was quite high. The indigo purity was quite high. And also it was much more easier. The temperature had come down roughly to around 200 degrees centigrade, which is like achievable in the industrial scale also. So once it was, once this method was developed, it was used by both BSF as well as by Hoist. Both these were German companies and German chemical companies. And they had totally, totally taken the, you know, they had taken it from pleasure and converted into large scale production of indigo. So both this company, BSF was a major one, Hoist was also there during that time. So this on the right hand side is the production, indigo production of BSF in the 1890s. You see, this was prior to Jonas Wager's method, which was given to them. So the industrial, we know always, the industrial synthesis had a very devastating effect on the Indian exports, which was bound to happen. By 1930, natural indigo almost entirely was replaced by synthetic indigo. And World War I was also on the way. So there were political repercussions also. So exports had already diminished. Indian exports of natural indigo fell from 187,000 tons in 1895 to 10,000, roughly around 10,000 tons in 1930. So see within a span of some few years, you know, how much it had decreased. By 1914, BSF was producing around 80% of the world indigo, synthetic indigo. And in 1988, capacity of the synthetic indigo had already reached 40,000 tons per year, out of which 12,000 tons were by these people, by these companies only. And few small amount was company coming from India, China, Mexico, South Korea. So by 2002, the Indian consumption was around 30,000 tons, majorly by the cloth industry, especially by the blue jeans. Plant derived product makes less than 1% of the total amount of indigo, which the textile industry uses is just 1% of total amount. Just see how it has decreased once when India was exporting it. Now India was like perhaps it has to import something of that sort. However, the synthetic method had its own share of difficulties. There were a lot of hazardous waste products which were produced. So like hydrogen cyanide, formaldehyde, ammonia, amide. So these had to be treated. And when treated, it's not a laboratory scale. These are not getting synthesized in laboratory scale like 10 ml or 50 ml. These were getting, we are talking in tons, tons. When I'm talking in tons, you are getting these by-products. You are getting these waste products. And you have to treat them. You have to treat them. So the waste products of course were treated, but a lot of it was also getting slowly disposed of into the environment. It was polluting the water bodies. Often the industries are near the water bodies. So it was polluting the water bodies. It was polluting the air, it was polluting the land, the soil. So people were starting, people had already started to use, by the time 2000 people had started to use, I mean, find out the synthetic way, but from, you know, from organic origin. So whether from glucose or using microorganisms. So a lot of research has been carried out. It's still getting carried out. But the problem is that when you take it into the large scale, handling of bio-reactors, there were difficulties in separating Indigo from the biomass, treatment of large volumes of organic, but these are not very easy. These are, you know, these are very large scales. And when I'm talking about the industry, it's like in tons you're talking about. It's not a small amount like what we do in the lab. So treatment of this waste for also very, it's also a very, very challenging job. So as of now, as of now, whatever information I have with me, we do not have a very biosynthetic method, which is like taken to the industrial scale, but a lot of research is going on. A lot of research is going on to, you know, to meet, so that, you know, at least convert this whole industry into some, you know, greener way, greener method. I hope so. And I definitely hope so that we should be able to do it in the future because blue or Indigo blue is in huge demand still now. From antiquity, still now it is still in huge demand. So apart from having Indigo as a colour giving substance or, you know, it also has shown some potential for applications in medicines, different areas of medicines, which are also in research under research. People have been trying to use Indigo in different ways also. And also it has been used in the areas of organic lasers, transistors. So all these are in the research phases. People are looking into it using Indigo and trying to, you know, increase its scope. So, okay, so yeah, so this is the last slide. And I hope I could take you briefly through a journey about Indigo, historical perspective, the different political pressures it underwent, and also its chemistry and the current scenario of its production and how it changed over so many, you know, centuries. So yeah, thank you everyone. Thank you everyone. So I have come across a quote that Indigo is a colour which has a history as vivid as itself. So indeed your presentation, your talk takes us through that history, its chemistry and development. And I believe at the end that you said that more research is going on in different fields of biomedical and all. So maybe it has a vivid future too. Yeah. So with that, I would like our viewers, if they have any questions, they can put them in the chat box in the comments. We have one question on YouTube. Is Indigo still used for Levi or other blue jeans? Indigo is used, Indigo is used but it has the Indigo which is getting used now is, you know, has a synthetic origin. It's not the plant-based which is getting used. Because plant-based, you know, to the whole production of production, we knew the plant-based is roughly 1% of it only. So Levi jeans is also the Indigo which is getting used has synthetic origin, it's an industrial made. But we do have, you know, we do, if not in Levi jeans, but in other dresses, especially in India, we have this, you know, natural Indigo made fabrics which are sold separately. So we have these. We do have that. Okay. Do we have more questions? Any comments? Thank you. Okay. Yeah. Okay. Thank you. Thank you all for listening. Yeah. You have liked that session. Thank you. There's one comment. Yeah. So there's no green chemistry for blue dyes. Blue dyes as such, I will not be able to say blue dyes because blue dyes encompass a lot of other dyes also. For Indigo people, that's what I'm trying to say. For Indigo people are trying to find out greener ways of, you know, and of course when I say greener way also, the hazardous waste products are treated and then disposed off into the environment. That is there, but that's in turn. So sometimes it may happen that some things are not getting properly treated and disposed off. People are looking into it. People are trying to find out different ways, you know, so that this whole thing can be done in much more greener way with less of the waste getting hazardous waste getting produced. There's a lot of research going on. Okay. So yeah, with that, I would like to thank our viewers for joining us on a Sunday and you can comment your questions and any comment if you have later. And also you can comment any topic you would like us to talk about in our future steamboat sessions. So yes, see you all next month on the second Sunday again. Till then have a nice time. Thank you. Thank you and running. Yeah. Thank you Vishal. And I would also like to thank the steamboat members for giving me an opportunity to talk in this session. So thank you everyone for all your support. So I'll stop sharing. Yes. So I'm logging out then. Yeah. I'll just save the chat. Okay. Thank you. Thank you very much.