Medieval Red Dye: Fun with pH
This class will cover the basic process of natural dyeing with cochineal (a period substitute for kermes; kermes is nearly extinct now and prohibitively expensive, and they are very similar bugs) as well as how alterations in the pH of the dyebath can alter the color of cloth dyed with a red dyestuff. A more acidic dyebath will produce a warmer shade, whereas a basic dyebath will producer a cooler shade. When working with cochineal/kermes, acid makes red and basic makes a purple. Madder yields orange and pink. These pH altering additives are vital ingredients in achieving a more precise shade of your choosing rather than just letting your chosen dyestuff dye whatever color it would like to be.
The basic method of dyeing is as follows: Mordant your fabric, prepare the dye vat, insert fabric and keep it moving as best you can, rinse, and hang to dry.
Our ingredients will be alum, cream of tartar, chalk, and cochineal, and 100% wool as our fabric. These mordants and dyestuffs are all food ingredients, but don't drink the dyebath, it is not very tasty and it has enough cochineal to turn your mouth rather red. Although a variety of other ingredients were used in period, including in the sample recipes, we will be using simple recipes to save time and avoid nasty things like arsenic.
A mordant essentially helps the dye to "stick" to the fabric. It bonds with the fiber and later with the dye, making the dye less likely to wash off or fade. Alum (potassium aluminum sulfate) was one of the favorite mordants in period, mentioned in many recipes, and we will use it today. Many period recipes do not mention a lot of things that we would consider essential to a recipe, such as precise quantities of mordants or dyestuffs to add to a vat. As a result, we must combine multiple period recipes to deduce what they would have done in some cases, and just guess as to some quantities.
Half of the wool samples have been prepared by boiling in alum and water, and half have had (cream of) tartar added to the alum and water. Cream of tartar renders these samples more acidic. Stockholm (see the period recipes list) recommends boiling for an hour and then leaving it overnight, whereas the Plictho only recommends boiling for an hour, and specifies that each pound of cloth should have half an ounce of alum and an ounce of tartar (for the acidic dyebath). These have all been left overnight. One recipe in Segreti per Colori recommends leaving the fabric to mordant for 3 days and 3 nights, so you have a wide range of mordanting time options.
Many recipes recommend adding more alum to the dye vat itself, so the mordanting liquid will just be topped off and more things added to it rather than discarding it. This is much more efficient. The Plictho implies that this may have been done in period, and certainly period arts and sciences were very efficient with materials and it would be unlikely that they would have discarded this.
For our acidic dyebath, the one with the tartar, we will proceed to add 6 ounces of pestled cochineal for each pound of wool. (I often put my dyestuffs in several small "teabags" - this saves a whole lot of time picking bits off of the fabric, and is plausibly one of the processes that could have been used but not mentioned, such as what exactly the "wheel" is - see illustration - or the form of the apparatus used to hold the dye vat.) We will also add some (eyeball it - a tablespoon or two for this smallish amount of fabric) more alum and tartar. This is a simplified version of the Plictho recipe to save time. The tartar will produce a warmer, redder color than you would get without it or with the addition of basic pH materials.
f53v from Die Hausbucher der Nürnberger Zwölfbrüderstiftungen c. 1433. This is the apparatus which appears, I believe, in the later 14th century, which makes dyeing much more efficient. The "wheel" (the rod with the crank) allows you to keep fabric moving and get it out of the vat more easily, while the "dye oven" as I call it holds up your dye vat and traps heat well. Stay tuned for my recreation of this majestic setup.
Both of these vats will be boiled gently (don't boil your vat over) for 1 hour. Kermes/cochineal recipes direct you to boil the vat, but madder must not be boiled if you use it or else it will turn brown instead of pink or orange. While period master dyers were so well trained that they could tell by sight what the right temperature looked like, I find that without the training from a 7 year full-time apprenticeship, I need a food thermometer to tell what temperature my vat is. We will be dyeing using a modern burner rather than a wood fire or "dye oven" with wood fire for safety and convenience.
During the dyeing process, it is both vital and period to keep the fabric moving. In period, this was done by agitating the fabric with poles and/or cranking it over a dye wheel. This keeps the fabric from wrinkling and forming pockets, therefore taking up dye unevenly and resulting in an unfortunate tie-dye look (this may be appealing to the modern eye, but period dyers were looking for a uniform shade).
Most recipes do not specify what you should do once your fabric is cooked. Segreti recommends washing it in water afterward, which I also recommend as some dye will inevitably run off your fabric and it is better to rinse now than to have it run all over your clothes. We will rinse in cold water and hang our samples to dry. If you would like you can wash it in warmer water at home, with soap, vinegar, etc. if you want to make very sure no more dye will escape.
Some period recipes:
From the Innsbruck Manuscript, c. 1330, Austria
“Take chalk in a pot and pour water thereon and mix it well together and let it sink to the bottom of the pot so that the water becomes clear and take that same water and boil the brazilwood well therein, until it is cooked and mix in alum and with it dye red zendel.”
From the "Stockholm Papyrus" ("Papyrus Graecus Holmiensis") c. 300-400
"Mordanting and Dyeing of Genuine Purple. For a stater of wool put in a vessel 5 oboli of alum (and) 2 kotyles of water. Boil and let it (become) lukewarm. Leave it until early morning, then take it off and cool it. Then prepare a secondary mordant (in which) you put 8 drachmas of pomegranate blossoms and two kotyles of water in a vessel. Let it boil and put the wool in. However, after you have dipped the wool in several times, lift it out. Add to the pomegranate blossom water about 1 ball of alumed archil and dye the wool by judging with the eye. If you wish, however, that the purple be dark, add a little chalcanthum and let the wool remain long in it. In another passage it is in the following way: But if you wish that the purple be dark, then sprinkle natron and a little chalcanthum in the dye bath."
From Segreti per Colori, a mid-15th century Italian manuscript
“To dye silk or cloth red: Take 1 lb. of silk, and 4 oz of soap, and put them into a cauldron with water, and let it boil until you see the silk appear starred. Then take it out, and wash it well in clear water until the silk becomes white; drain it well, and wring it with your hands, and then spread it out, and this is done when the silk is not boiled. Then take 4 oz of alum in another small vase and boil it, and dissolve it in clear water, and when it is dissolved take another large vase, and fill it with fresh water, and put the alum into it, and then put in the silk, and let it remain 3 days and 3 nights, and then wash it and stir it about well with fresh water, wringing it well with your hand until the alum is washed out. Then take a kettle of fresh water, and 3 oz of powdered brazilwood, and let it boil until reduced one third, then fill it up with fresh water, and boil it again until reduced one finger’s breadth. Then take it off the fire and divide the water into two portions, and into one of these put the silk and let it stand until it is cold. Then wring it with your hand, and put it back into the other water which you reserved, and let it be as hot as you can bear your hand in it. Then drain it and wring it well, and spread it out in the sun and it will be fine.”
"To dye very fine scarlet. -Take 1 lb. of verzino columbino well ground, and soak it in clear water for the space of two days, and then put it into a boiler containing 3 or 4 bocali, to boil until reduced by one-third, add to it 2 oz. of quicklime and 3 oz. of roche alum; and if the colour is pale add 2 oz. of fenugreek; and if you wish to have it of a fuller colour add a fogliecto of boiled lye and it will be of a fine colour."
From the Plictho of Gioanventura Rosetti, c. 1548, Venice
"To dye cloth a very beautiful scarlet, in the manner of this City of Venice. First weigh your cloth, and for each piece [pound] of cloth use about 6 ounces of grain. For the mordanting, for each pound of cloth, use a half ounce of roche alum, and one ounce of white tartar well pestled and sifted. Have a cauldron, and have clear water and put into it the alum and the tartar. Make beneath a good fire to the end that it wants to boil. Then put in the cloth and make it boil continually for one hour with a good fire below. Then you will take out the cloth and send it to be washed in water that is well running and wash well and then prepare the full cauldron. Set it on the fire and see that inside there be four pails of strong water, well fatted and well pungent, together with the water. As it shows signs of wanting to boil, put in the grain but first see that it is well pestled. When it is about to boil put in the cloth and dive it, that is, poke it beneath, and give if four or five rounds on the turn wheel. Then remove out the cloth and let it cool. Then send it to wash in running water. Then prepare a new bath and give it two or three baths, that is with the bran, and for each bath one pound of roche alum and one pound of tartar. If the cloth is too open, give it a new bath, that is a quarta of bran without tartar, and one pound of arsenic well pestled. Note that it needs to boil one quarter of an hour, each and every new bath, with bran. Also, if the cloth were to be overloaded, give it a new bath with bran without tartar, with a pound of roche alum."
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