Using Plant Dyes to Dye Leather - My Experiment
Some natural plant dyes work really well on veg tan leather. Veg tan leather is already prepped for a number of leatherwork applications, so it’s dry, clean and thirsty.
I began my experimentation with various veg tan scraps. Some were strap-like up to 6-8oz leather and others were wider strips of 2-3oz leather. I have no idea how old the leather was or what they were scraps from (I inherited them as scraps).
Dyeing essentially occurs in two stages. 1) Mordanting, and 2) Dyeing.
The mordant preps the leather to accept dye. The mordant I used is alum (potassium aluminum sulphate). In fact, all the dyes I used were from Maiwa School of Textiles. Since I had no idea what I was doing or what would work, I got this kit of multiple dyes to experiment with in small quantities. I now know which ones worked best to go back and buy more of in larger quantities.
The dyes are intended for textiles such as fabric and wool. There is no mention of how they may work with leather, so I generally followed the ‘protein’ dyeing instructions. It’s important to remember that leather is an animal product and treat it with respect. It doesn’t respond well to excessive heat such as boiling; you can scald, burn or curl it. A basic rule of thumb I use is that if it’s too hot for my hand, it’s too hot for the leather. With that in mind, I bypassed all the instructions about boiling and achieving certain temperatures, though I did use hot water from the tap.
1) Preparing Leather with Alum Mordant
I found a large enough plastic jar to hold a mordant solution for all of my scrappy samples at once. I totalled their weights on a food scale (about 1000 grams) and then weighed out 10% of that weight in alum (about 100 grams). I dissolved the alum with the hottest water I could get from the tap and filled it about half way, added the leather samples and topped it up the rest of the way. Then I screwed the lid on, gave it hardy shake and let it sit for about an hour. The instructions suggested using rain water. I figured since we have pretty good chlorine-free water here and a water filter on the house, it wouldn’t matter much. I was right.
Mordanting is an important step. It allows the leather to become soft and porous, especially if it has been sitting for a long time. You will also notice that tannins leach into the mordant solution staining it brown, so to some extent the mordant cleans and releases particles from the leather. Most importantly, the mordant fixes the future dye and improves its colour fastness and evenness. The samples I tried without pre-mordanting turned out blotchy and uneven. It was an interesting effect, but would only work with the more intense dyes and would be disappointing if you wanted even colour tone.
After an hour of sitting in the mordant solution, I drained out the entire bunch of samples in the sink (a stainless steel, basement sink) until the leather was no longer soaking wet.
2) Preparing Natural Plant Dyes for Leather
I found 12 canning jars or recycled jars and put two teaspoons of a different dye in each one. I could have been more precise and followed the recommendations regarding the strength of each dye, but I’m not really that into instructions. I prefer the experimental route.
I added enough water to dissolve the dye in each, and used a wooden chopstick to crush the dyes that stubbornly wanted to remain in clumps. Then, one-by-one, I filled 3/4 full with the hottest tap water, added pieces of pre-mordanted, wet leather scraps (by rolling them in coils), and than topped up fully with hot water. For each one, I added a small piece of ‘junk’ leather so I could do an early colour test to see how the dye was setting over time. I put the lids on and shook and inverted the jars till the dye looked evenly dissolved.
Some plant dyes produce richer colours if you add iron. I doubted that some of the green and light brown dyes would have much effect on the leather on their own, so I took iron capsules (that were supplements from the drugstore) and cut them in half to empty into the dyes. I did this for Coreopsis, Quebracho and Dyer’s Broom. Instantly the dye solutions took on a richer brown hue.
After a couple hours, I opened each jar, removed the colour test strips and decided to leave each one overnight except for the Logwood dye. Logwood has a lovely purple for a couple hours, but turns to a dark brownish purple if left too long (unless this is what you want). I also removed each piece of leather and re-rolled it so the opposite side would be facing the outside of the jar. This is important because it allows the dye to soak into the stretched surface. Otherwise you will have stress marks on the good side of the leather when you are working with your final product. The re-rolling also provides an opportunity to dislodge any part of the leather that may have been touching inside the jar and resisting dye. Throughout the process, I revisited the jars as many times as I could to shake them and prevent dyes from sedimenting at the bottom of the jar.
The next morning, I opened each jar one-by-one in the sink and carefully removed the leather with my hands. You need to be careful because wet leather (and especially leather that has soaked over night) is easily indented, which will produce marks for life. Each batch of samples was left to bleed out in the sink until I could pick it up with out any dye solution dripping out. This doesn’t take long because the leather is quick to wick up extra moisture. I hung the leather over a shower rod with a protective mat underneath to dry.
Results of Natural Dyeing on Leather
Some natural plant dyes work better than others.
The pink, purple and reddish dyes worked brilliantly well. Both Lac and Cochineal produced a lovely, rich raspberry colour, with Cochineal being a brighter hot pink. Logwood produced a beautiful, warm, earthy purple. It can be used in greater quantity and overnight to saturate into a dark, rich purplish-brown.
My favourite colour out of the mix was Madder Root, which came as both Standard Madder Root and Rich Madder Root. With slight variation, both produced a beautiful, natural orangy-red with salmon hues, almost like terracotta. Once dry, the colour samples lightened up quite a bit. Next time I would stick with the Rich Madder Root variety and make a more concentrated dye.
Some of the browns also turned out very nicely, offering a wonderful natural alternative to the oil dyes that are available. The Quebracho (with iron) produced the richest brown. The Chestnut produced a less saturated greenish brown and the Dyer’s Broom (with iron) was quite similar but more saturated than the Chestnut.
The green and yellow dyes (Weld and Goldenrod) had minimal effect. The leather was slightly altered from the peachiness of veg-tan colour, but not in any significant way. Apart from documenting the experiment, I would redye them again before using.
The best greenish hue I got was from Coreopsis (with iron). It cooled down the colour of the veg tan with a sheer saturation of olive green.
Next Steps with Plant Dyed Leather
After the leather is dyed and dried you have a pretty good indication of its final outcome. Keep in mind that some dyes are not as colourfast as others (and I’m not sure what they are yet). Depending on your project, you can use various treatments in accordance with typical leather work.
Before treating the leather, you might consider letting the leather sit in the dye longer, or sit in another dye. It worked well to double-dye a strip in Lac, even when the dye solution was almost a week old and on its second use. I put the jar with the leather and dye in it in a big soup pot and heated it up to pre-boil on the stove with the lid on loosely, and then turned the heat off and let it sit. The sample turned into an even richer raspberry. I guess you have to be fine with experimentation and unpredictable results to do this. Absolutely do not let the leather boil in the pot. It will disintegrate and burn (I learned this the hard way). The heat re-activates the dye but you shouldn’t put the leather in until it is cool enough to put your finger in without burning.
The leather will be pretty crunchy and dry after being kept submerged in water overnight and then drying. If you just want a quick indication of its potential, buffing with a soft piece of cotton will shine up your samples and make them less rigid. You can also work in scant layers of oil to slowly loosen it up and add life. Apply oil thinly and evenly on both sides so you don’t mess up your dye job.
The dye does not saturate all the way through the leather, so if you’ll be doing any trimming, these will now be undyed, exposed edges that you’ll have to deal with (this includes beveled edges and stitch grooving lines). I don’t find this to be a problem, but if you started your project with a game plan and pre-cut out and punched your pieces, you could avoid this.
I found it no problem to re-wet the leather and do metal stamping. You can also paint the leather and use various other conditioners like beeswax or carnuba polish in the usual way. I like the idea of using a wax finish as it also seals the dye and prevents it from leaking out later, such as onto hands or in the case of dog collars, around the dog's neck.
I’m going to keep my dyes around in jars for awhile in case I find any more scraps. I may also re-submerge my existing samples in their dyes after I have them bevelled and punched into products just to add some colour tone to the cut edges.
Where to Spend Your Plant Dye Dollar
As I budget for future natural dyes to use on veg tan leather, I can tell you that based on these results I will be putting my money into the following:
- Madder Root (reddish-orange)
- Quebracho (rich, warm brown)
- Coreopsis (greenish-beige)
- Cochineal, Lac (raspberry)
- Logwood (purple)
I’m so happy that this turned out to be a worthwhile experiment, and I hope any information I’ve provided here can assist others in fine-tuning their dyeing process. You can see the dog collars that I made from the dyed straps here.