First batch of indigo and the importance of taking notes.

The first batch of indigo was a small trial batch on 15L because I heard so much about the difficulties with indigo and that it was supposedly a lot trickier than e.g. madder and onion skin. As a low volume trial, I only dyed some swatches and some left over yarn that I had lying around. In my previous entry I covered the basics of indigo dyeing, look it up here if you’re interested.

Indigo dyed wool and yarn
Indigo dyed fabric and yarn.

From the left it’s wool, silk, wool, wool, store bought yellow wool and grey wool. Everything turned out pretty uneven but it’s not realistic to expect perfect result on the first attempt. Besides, it’s indigo, you can always re-dye it for a more evenly dyed fibre.

Considering the instructions for indigo batches I always use Sandström and Sisefsky (1970) for this purpose. Since I don’t know the exact chemistry behind this process (!) I use a linear model to keep the same ratio in each batch. That is, I just multiply or divide the value in the existing instructions to fit the fixed variable. The fixed variable differs from time to time, sometimes I have a finite amount of indigo, sometimes I have a certain amount of yarn I want to dye and sometimes there is a volume limit on the cauldron I am using. This makes me re-calculate everything before dyeing but that’s not a bad thing because I like to have time to think things through, which is something that I am forced to do in such cases.

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A standard setup for recalculating batch sizes.

As you can see, I try to write down the date, mark the fixed variable and then write down the other amounts used so that I would be able to re-do the exact same thing if needed. In that way, it’s easier to say that a certain hue can be made or if I would need to dye some more fabric or yarn in a similar hue.

Concerning the chemistry of the dyeing process, I aim to get a better understanding of the chemistry in time but this is a work in progress. If I am able to do that I think that it is possible to do several process optimisations, which would result in the usage of less material and heat but still having good water and light fastness in the dyed material. Using a linear model is often a very simplified solution, many chemical processes are not well represented by a linear model and it is possible that it’s the same case with the indigo dyeing process. I’ll get back to you if I find anything worth sharing.

The larger piece of wool fabric that you see to the left in the first picture was later on used as a lining for a 14th century womens hood, which is a comfortable use of an uneven dyed fabric since most of it won’t be seen anyway. Tablet-woven edges done using yarn in the same light blue hue from the same batch, just to keep up with the latest reenactment fashion ☆
My hood is made from leftovers so it’s a little lacking at some points but if you want an excellent tutorial for this hood you should check out Katafalks tutorial here.

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14th century womens hood with tablet-woven edges.

I still haven’t done anything with most of the yarn since I don’t have any reenactment related ideas, suggestions are welcome. Worst case scenario, it’ll be used for modern knitting.

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Dark blue is two dips, light blue is one dip.

Smaller batches are always useful for learning and also very easy to handle so I’d definitely recommend it as a good starting point. Developing a habit of writing things down will also make it easier to backtrack your work, to learn from it and to know what kind of colour you will get from a specific setup. Notes are a superior tool in order to communicate methods and results to others; also, you don’t need to remember everything if you have it written down. Overall, information exchange and feedback is fundamental for improvement and to avoid having everyone repeating the same mistakes.

Combine this with a sample set of each batch and you will be on your way to greatness. Now get a fancy notebook and get going.

 

References

Sandberg, Gösta & Sisefsky, Jan (1981). Växtfärgning. 5., [omarb.] uppl. Stockholm: Norstedt.

A comparison.

Sometimes some things just works out better than expected. Here is a comparison between some store bought fabrics and plant dyed yarn. These plant dyes were made during a Battle of Wisby workshop in 2013. The green yarn is birch leaves, the darker green is birch leaves with additional iron sulfate and the red one is madder.

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Store bought fabric, plant dyed yarn.

Socks and tansy dye.

I’ll try to dig up som old corpses, dyes and crafts that I have done over the years to start with. First out is my very first plant dyed yarn! It was 200 gram of a thick, bone white, single ply wool yarn from Marks & Kattens.

I like thick yarns to naalbind socks and mittens, because it’s quick work and becomes soft, though I have heard that socks made from thicker single plied yarn supposedly gets worn out more easily. I have a pair of socks in this yarn and this has yet not happened to me but maybe I just have baby soft feet incapable of causing harm (not true) or feet sweaty enough to full the wool instead. For example, I can show you how socks made from this yarn has turned into a nice felted sole (if you’re into that kind of thing). But then again, these are just event socks; which means I only use them 1-2 weeks a year so the non existent wear and tear of these socks is not representative of everyday use.

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The black spots underneath the socks are from the nails in my late medieval pattens. The mittens are in a very fancy steel grey colour.

Findings of a single plied sock is yet to be found, I somehow have an idea of it mostly being 2-ply, 3-ply and 4-ply yarn but right now I can’t seem to find anything about this except  this small picture on the sock from of the Coppergate findings. If anyone can help me out with a better source on this I would welcome it.

Back to the dye! Done in December 2014, it is the most unregulated and unknown dye I’ve done since it was made from leftovers from a tansy bath that I got from my excellent partner in reenactment crime, Anna (check out her blog!). As such, I have no idea of weight ratio or actually anything about what this was. It could be a mixture of plants for all I know. However, the dye was made with about 2 L of left over bath so I just diluted it with enough water so that the wool could move around and get a even spread of dye in bath. The pot in the picture is a 15 L pot so I’d say that I might have used a ratio of 1:4 of left over dye bath to water; I don’t know why I used such a small amount of water, I should’ve used more but who knows, maybe I was having a bad day…

In the case of dyeing, if your pot is 50L or less, I’d recommend to use as much water as possible. Even though it’s diluted it’s still the same amount of dye just less concentrated (if anyone remembers m [gram] / M [gram/mol] = n [mol] where n is the mole that represents the amount of substance, in this case the amount of dyestuff. Using the formula for concentration c [mol/m3]· V [m3] = n [mol] we can see that n is unchanged since an increase in volume would affect the concentration as well and as such leave the mole unchanged). A larger volume of water is beneficial for the diffusion of the dye bath so that the dye can spread itself evenly through the bath and uneven colouring can be avoided (Dumitrescu et al., 2008; Lewis and Rippon, 2013; Mehrparvar et al., 2016). If possible, I will make a separate blog post where I briefly elaborate further on relevant thermodynamics, diffusion and heat transport.

Anyhow, don’t let confusion get to you just because I used some different words, standardised units and chemical formulas; all of you probably can intuitively come to terms with the idea that more water is needed to give a good flow throughout the yarn and it’s not bad to apply some basic science or analysis in your everyday life. Who knows, it might come in handy later on (the real struggle here is for me to avoid being overly vague or incorrect because if I at some point am, the internet hellhounds will haunt me for the rest of my natural life). Sandström and Sisefsky’s (1975) recommendation on this is a 5 L bath per 100 gram wool which I’d say can be considered a guideline as good as any.

The pre-mordant used was alum, KAl(SO₄)₂·12H₂O but is also known by the name of aluminium potassium sulfate dodecahydrate, used with the generally recommended ratio of 20wt% mordant (Conradi-Engqvist, 1978; Kierstead, 1950; Sandberg and Sisefsky, 1970). Deviations from this recommendation is Vrande (1982) and Råbergh (1978) with 15wt% alum but instead they commonly uses additionally 10wt% tartar or uses post-mordants with a 5wt% of copper sulfate, CuSO4, or iron sulfate, FeSO4, respectively.

It is sometimes considered that older recipes and ratio for pre-, post-, and meta-mordants are overdoing it concerning the recommended amount of mordant; I have not yet done any further testing of different mordant ratios since I only have two pots for dyeing at the moment and as such, I currently consider myself lacking enough equipment to do any good mordant ratio variations. Nevertheless, I think I’d like to give it a go at some point. But yes, I’d be inclined to agree that less mordant can be used but it will affect both the colour and the fastness against water as well as light. Less mordant means less colour intensity and also less wash fastness and less resistance to light. That is, using an insufficient amount of mordant will cause most of the dyestuff to eventually be washed out. Using mordant attaches dyestuff to the fabric due to the complex coordination properties of metals (Lee and Kim, 2004; Uddin, 2014; Mehrparvar et al., 2016), e.g. you can get different hues as well as increased levels of fastness against water and light using mordant (Waheed and Alam, 2004; Burkinshaw and Kumar, 2009; Dumitrescu et al., 2008).So, again,  it all depends on what you want. If you want a dyed material with a well defined colour that should be relatively unaffected by both sunlight and washing, it would be suitable to use mordants. Nevertheless, it is also good to use resources sparingly and using too much mordant of any kind is a waste, the question is; how much is too much? What’s the smallest amount that can be used and still get an effect?

Anyhow, enough mordant talk for now, I will have to get back to that subject later.

I don’t have any notes from this dyeing but I think the pre-mordant was done for 60 min at ~90°C and then leave the wool in the mordant bath until cooled. Then I let it hang for a day or two to dry before it was time for the tansy bath. Same procedure with the tansy bath, 60 min at~90°C, let the wool cool in the dye bath.

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A carbonara of tansy, wool and doubt.

Despite not having any exact knowledge of what I was doing it turned out Very Nice.

tansy2wm
Sunshine yellow meets Falu rödfärg. Note the green (previously blue) yarn used to tie it together.

Considering the colour intensity of the yarn, I could’ve probably used the bath for several more dyes but for I had no further dyes planned so I didn’t. The plot twist of this story is that the yarn was supposed to be for my friend in Stockholm but the package was lost or stolen from the letterbox during the christmas holidays. I mourned for a couple of months but I still have a small piece left that I took for reference.

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Indoor light references.

Anyhow, this is so far the most tragic tale I have in the art of plant dyeing so stay tuned for happy excitement as we prod at the dyes of the past.

References

Burkinshaw, S. & Kumar, N. (2009), ‘The mordant dyeing of wool using tannic acid and FeSO4, part 1: Initial findings’, Dyes and Pigments 80 (1), 53 – 60.
URL: http://www.sciencedirect.com/science/article/pii/S0143720808000752

Conradi-Engqvist, Cecilia (1978). Spinna, växtfärga och forma av tråd: från naturfiber till textil. Spinna ull och lin och forma av tråd : med färg- och kompositionsövningar : studieplan. Stockholm: LT

Dumitrescu, C., Gorghiu, L., Olteanu, R. & Bumbac, M. (2008), ‘Natural dyes used in tinctorial practice’, Bulletin of University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca. Agriculture 63 (0).
URL: http://journals.usamvcluj.ro/index.php/agriculture/article/view/1355

Kierstead, S.P. 1950, Natural dyes, , United States.

Lee, Y. & Kim, H. (2004), Dyeing properties and colour fastness of cotton and silk fabrics dyed with Cassia tora L. extract, KOREAN FIBER SOCIETY, SEOUL.

Lewis, D.M., Rippon, J.A. & Ebook Central (e-book collection) 2013, The coloration of wool and other keratin fibres: edited by David M. Lewis, Department of Colour Science, University of Leeds, UK and John A. Rippon, CSIRO Materials Science and Engineering, Australia, Wiley, Chichester, West Sussex.

Mehrparvar, L., Safapour, S., Sadeghi-Kiakhani, M. & Gharanjig, K. 2016, “A cleaner and eco-benign process for wool dyeing with madder, Rubia tinctorum L., root natural dye”, International Journal of Environmental Science and Technology, vol. 13, no. 11, pp. 2569-2578.

Råbergh, Hilkka (1978). Färga garn och tyg: växtfärgning, syntetfärgning på bomull-batik, syntetfärgning på ull. Västerås: Ica bokförl.

Sandberg, Gösta & Sisefsky, Jan (1981). Växtfärgning. 5., [omarb.] uppl. Stockholm: Norstedt.

Uddin, M.G. 2014, “Effects of Different Mordants on Silk Fabric Dyed with Onion Outer Skin Extracts”, Journal of Textiles, vol. 2014, pp. 1-8.

Vrande, Iet van de (1982). Växtfärgning av ull. Göteborg: Wezäta.

Waheed, S., & Alam, A. (2004), Studies of some natural dyes, JOURNAL-CHEMICAL SOCIETY OF PAKISTAN, 26, 255-263.

Common misconceptions about plant dyeing.

I was going to wait a while before doing this kind of post but I was struck with sudden inspiration when I stumbled upon a Facebook group that focuses on plant and mushroom dyes. What is plant dyeing? Or, as it sometimes is referred to, natural dyeing?

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Yours truly doing a batch of indigo dye in January 2017.

Wikipedia is generally considered as an unreliable source but it somehow reflects society and the general public, and as such they say the following: “Natural dyes are dyes or colorants derived from plants, invertebrates, or minerals. The majority of natural dyes are vegetable dyes from plant sources—roots, berries, bark, leaves, and wood—and other biological sources such as fungi and lichens.”

The alternative to plant dyes is synthetic dyes which are dyestuff that is not naturally occurring. The first synthetic dye was Mauveine in that was synthesised in 1856 and subsequently launched on the market in 1857. Even though picric acid was prepared as a dye as early as  1771, the foundation of the synthetic dye industry is generally attributed to the Mauveine synthesis and commercialisation (Christie, 2001). Before that point, all dyes were derived from natural sources.

But today plant dyeing seems to have a unique meaning only known to the user themselves. The general consensus is that fibres are being dyed but the means of doing it varies. For some, it means using plants for dyeing; for others, it means only using natural sources they can harvest out in the nature by themselves to dye with; and for a few it means to dye only using things with trivial names (incorrectly but commonly referred to as a “chemical free” process). I will try to avoid going into semantics about what is and is not a chemical by posting a link to this blog post about “What is – And What Isn’t A Chemical?“. As much as I’d like to tell you everything, I don’t have the time (and besides, who says you’re going to believe me?). But if you DO believe me, let me sum things up by saying that every material is a chemical, even if it exists in your home and has a trivial name.

To use a plant dye example; the chemical Ca(OH)2 is commonly referred to as slaked lime, which is constantly presented as an alternative to the chemical ammonia, NH3, in indigo vats. Unfortunately, they are both chemicals so if your aim is to do a dye without chemicals you have failed to understand the fundamentals of dyeing (and chemicals). Although, there are other reasons to use Ca(OH)2 instead of NH3 and vice versa but replacing one with another in the hope of becoming chemical free is futile work. Even that handmade natural oak-spirit-soap you bought at the last Carpe Diem-fair is made out of chemicals; even though the individual who sold it to you guaranteed it was not. There is no way around it. Minerals are also naturally occurring (Richardson, 1997), which makes copper sulfate, Cu(SO)4, legit as a plant dyeing material if we go by the the definition of plant dyeing (plants, minerals, invertebrates; derived from nature; naturally occurring etc.). And as such, we have the conspiracy unfolded right here, similar to when Frank Thorn realises the plot twist of the movie Soylent Green;

Nature is chemicals! They’re making chemicals out of nature. Next thing they’ll be synthesising organic molecules themselves. You’ve gotta tell them. Chemicals are naturally occurring!

soylent-green
In this scenario I’d say that I am Frank Thorn trying to tell the truth to a people in denial.

But really though, I don’t think this comes as surprise for anyone (neither did the soylent green revelation!). I mean, where else would chemicals come from, the highly unnatural space? And, now that we think about it, are we sure that space isn’t natural as well? Anyhow, I do feel the need to mention that there exists a general idea of what is and what is not chemicals even in the field of chemistry; because we are also, believe it or not, a part of society and its norms. It is considered childish and unnecessary to refer to everything as chemicals all the time because it’s a basic fact which tells us nothing new. But on the other hand, in communication you have to specify what you’re talking about and herein lies the difference; you can’t just say chemicals if you want other people to understand you! You should explain what chemical you’re referring to, which isn’t that much of a stretch really since you probably have one in mind already.

I don’t believe you! If everything is chemicals then how do I know what is toxic and what is not?

In case you didn’t know, table salt can be toxic to humans. Apple seeds contains cyanide and cyanide is also toxic to humans (Holzbecher et al., 1984). All in all, there is stuff like this everywhere and about everything can be toxic, it’s only a matter of concentration and dosage. The thing is, you don’t digest or wash your eyes with washing powder, hairspray, rubber, deodorant, hair dye, thinner, oil, nail polish or shampoo because you know that it might not be good for you. You seldom use these things outside of its intended purpose because you also know that it might become weird. And don’t get me started on people who smoke and drink but are afraid of chemicals eventually being hazardous… Nevertheless you don’t hesitate to use it in your everyday life. But for some, reason, this kind of thinking completely disappears as soon as the word chemical is involved. Which is weird, because it’s basically the same things going on there. There ARE information and literature on how to plant dye and what to use and how. Follow those instructions and you’d be fine. Another source of information is to check out the (Material) Safety Data Sheet (M(SDS)) for a certain chemical. Here is a MSDS for table salt.

A short, but very unsatisfying, summary would be to implore you to use your common sense and you’ll be fine. If you still want more I’d recommend to study toxicology.

But there is too much information, I can never remember any of this!

You don’t have to, most people use books to write down the most important things and there is always the internet to enlighten us.

Why did you have to make everything difficult, my way of thinking and evaluation is much easier!

I didn’t make anything (except this pesky blog), nature did.

But I am sure that people used only onion skins before the first synthetic dye, none of these mordants and acids! Those are all 20th century ideas!

I am not so sure. Unfortunately, as we often do in historical reenactment, we lack a lot of sources. Though one source that we do have is from a handwritten manuscript from around 1860; that is only a few years after the first synthetic dye was created and the processes described in manuscript involves no synthetic dyes. In fact, all these recipes described would soon be abandoned for the much more efficient and less costly synthetic dyes (Sisefsky and Sandberg, 1979). The manuscript has one example for dyeing blue wool yarn and it involves potassium cyanide (KCN), hydrochloric acid (HCl), disulfuric acid (H2S2O7), potassium aluminium sulfate (alum, KAl(SO4)2) and potassium bitartrate (cream of tartar, KC4H5O6). How’s that for a cocktail? Kind of put our modern concern about using a 20wt% alum mordant at a shame. Of course this doesn’t mean that this is what was used in the earlier centuries but we can at least say that these chemicals are not exclusive to the 20th century and their use in plant dyeing processes precedes the 19th century development of the synthetic dye industry .

I dye only using onion skin! I am chemical free.

Pelargonidin is what is in the dyestuff of onion skin (Uddin, 2014). If you’re not using a mordant, it would be sufficient to just say that you’re dyeing without using a mordant.

Surely I use less hazardous material than in the industry? My environmental impact has to be less than if I’d buy the industrially dyed material?

The current industry has had several iterations, process optimisations and experience which generally makes the industry a lot more efficient than a single individual with little to no technical equipment and experience. Most developed countries also have a lot of regulations that is to be followed regarding the process and its emissions, no one will measure your own amount of trace metals in your plant dyes (Griffiths, 1984). As I previously mentioned, synthetic dyes are far more efficient than plant dyeing which means you’d generally consume less resources using synthetic dyes compared to plant dyes (Sisefsky and Sandberg, 1979). The difference here is to how to view the emissions; if you compare emissions and resource consumption per kilogram of dyed material, the industrial dye would probably be using less resources. A common theme is that there is a lot of transport involved in production, which is not good thing for the environment but also makes calculations more difficult. Even so, there are ways that these are accounted for (an example would be the Life Cycle Assessment) but you will always have to limit the analyse. I’ll try to explain this with an example; if you’d dye yarn that was made at the farm next door you’d be responsible for less emissions than if you’d buy imported yarn. But then again, if the sheep that made the wool at the farm next door lacks food in the pasture and needs to support feed and then that food needs to be transported there, should that transport be included in the emissions for the yarn? And where was that food grown and using what fertiliser? As you probably understand, this thinking can derail pretty quickly but I hope you see the problem with deciding a number for any of these emissions and impacts which is also why you should be critical to anyone producing such numbers, what is included and what is not? Often the numbers are in favour of whoever is presenting them so my advice is to be critical.

A summary of this would be to say that it’s impossible to know but an individuals plant dyeing process is probably more inefficient than the industry and has an unknown quantity of residuary chemicals in it (unless you analyse every batch, which would be cool but very expensive but at least you’d know what you’ve got). The industry can, of course, also have an unwanted quantity of residuary chemical but this is why we invest in quality and try to only buy fabrics and clothes from countries with regulations and decent working conditions, right?

My dyes DO become resistant to both light and water if I do it using only the dyestuff like blueberries/lupins/beetrot and no mordants!

No, they don’t. What happens is that you get a dyed material that WILL be drained of colour when exposed to water or sunlight (Burkinshaw and Kumar, 2009; Dumitrescu et al., 2008; Waheed and Alam, 2004). If you keep the dyed material away from water and sunlight things then you’d be fine but you’d also be living in a very dry and dark place. If you aim to be eco friendly, natural, climate considerate, environmental friendly or whatever buzzwords you use in justification then consider both the time, energy and work that you put into this. If you’re using any kind of heating in the dyeing process you are literally wasting energy and time; not to mention if you use wood as a fuel for heating the bath which has a LOT of exhaust gases that are harmful and currently not very popular (Bari et al., 2010;van Lith et al., 2006; Tissari et al.,2007).

I only use plant dyes in a cold bath and using sunlight so I am the most environmental friendly dyer there is and I am always pleased with my dyes and colour hues!

Good for you, get back to me when you can dye 2 kilograms of heavy wool evenly with a deep colour intensity while also getting water and light fastness in a cold water bath at pH7 using only dyestuff. Snark aside, if you HAVE achieved something like what I just said in a reproducible and controlled manner, please do share it with the world (that shit would be Nobel prize worthy)! That would be an amazing feat and of great benefit to the whole planet.

The question to ask in these cases is, if all kind of processing and chemicals are to be avoided at all costs then why dye it in the first place? The most natural way to avoid any kind of dye process is to NOT dye. Personally, I think that the natural colour and hues of wool is superior to many other hues, this is why a large part of my reenactment kit is non dyed wool. If you completely want to avoid any kind of chemistry happening then plant dyeing, or any kind of dyeing, is not for you. And before you even think it, there is nothing like good or bad chemistry; nature doesn’t work that way. Endless energy consumption is something to be avoided as well as pollution. Water is a resource and electricity doesn’t spawn spontaneously at the energy company, globally it is often a result of combustion (often coal) and somewhere there is a exhaust coming from that energy production. Is it worth the time and energy if the result will fade within a month?

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Sol Roth waiting for a water refill so that he can re-dye his 25 grams of lupin dyed yarn; it’s totally his favourite shade of green.

On the other hand, there are several other things you can do if you want a more sustainable lifestyle. Some examples would be to eat less meat, promote local farms and production, don’t throw away food, travel less (unless by foot, bike or sailing), recycle, repair, invest in quality and so on. And my primary advice is to consume less. Simply put, buy less shit. Remember, it’s not a bargain if you don’t need it.

In the end, however, everyone does as they please but be aware of what you’re doing and the reasons for doing it. It is totally ok to plant dye for your own sake, and peace of mind; I encourage that since that is what a hobby is about! But don’t do it for the wrong reason or try to claim the moral high grounds by saying that it’s more natural (what even is natural? Infant deaths, scurvy, polio, venomous snakes, anaphylactic chocks, cyanide, dental cavities, space?) or without chemicals (IT’S NEVER WITHOUT CHEMICALS!). Instead, to specify what you’re avoiding and for what reason would be a better way of communication if you want to show some sort of situational awareness and at the same time be understood by other people.

That’s all for now folks, peace out!

References

Bari, M. A., Baumbach, G., Kuch, B. & Scheffknecht, G. (2010), ‘Temporal variation and impact of wood smoke pollution on a residential area in southern germany’, Atmospheric Environment 44 (31), 3823 – 3832.
URL: http://www.sciencedirect.com/science/article/pii/S1352231010005017

Burkinshaw, S. & Kumar, N. (2009), ‘The mordant dyeing of wool using tannic acid and FeSO4, part 1: Initial findings’, Dyes and Pigments 80 (1), 53 – 60.
URL: http://www.sciencedirect.com/science/article/pii/S0143720808000752

Christie, R.M., Royal Society of Chemistry (Great Britain) & Books24x7, I. 2001, Colour chemistry, Royal Society of Chemistry, Cambridge.

Dumitrescu, C., Gorghiu, L., Olteanu, R. & Bumbac, M. (2008), ‘Natural dyes used in tinctorial practice’, Bulletin of University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca. Agriculture 63 (0).
URL: http://journals.usamvcluj.ro/index.php/agriculture/article/view/1355

Griffiths, J. 1984, Developments in the chemistry and technology of organic dyes, Blackwell Scientific, Oxford.

Holzbecher, M. D., Moss, M. A. & Ellenberger, H. A. (1984), ‘The cyanide content of laetrile preparations, apricot, peach and apple seeds’, Journal of Toxicology: Clinical Toxicology 22 (4), 341–347. PMID: 6098693.
URL: http://dx.doi.org/10.3109/15563658408992565

van Lith, S. C., Alonso-Ramírez, V., Jensen, P. A., Frandsen, F. J. & Glarborg, P. (2006), ‘Release to the gas phase of inorganic elements during wood combustion. part 1: development and evaluation of quantification methods’, Energy & Fuels 20 (3), 964–978.
URL: http://dx.doi.org/10.1021/ef050131r

Sisefsky, Jan & Sandberg, Gösta (1979). Receptsamling från Schwartzska färgeriet i Borås efter handskrivet original från 1860-talet på Borås museum. Borås: Borås museum

Richardson, H. W. (1997), Handbook of copper compounds and applications, CRC Press Tissari, J., Hytönen, K., Lyyränen, J. & Jokiniemi, J. (2007), ‘A novel field measurement method for determining fine particle and gas emissions from residential wood combustion’, Atmospheric Environment 41 (37), 8330 – 8344.
URL: http://www.sciencedirect.com/science/article/pii/S1352231007005754

Uddin, M.G. 2014, “Effects of Different Mordants on Silk Fabric Dyed with Onion Outer Skin Extracts”, Journal of Textiles, vol. 2014, pp. 1-8.

Waheed, S., & Alam, A. (2004), Studies of some natural dyes, JOURNAL-CHEMICAL SOCIETY OF PAKISTAN, 26, 255-263.