I've been collecting them in a bag in my freezer for the past month, and when I hit 15 (ok really I just wanted to give it a go already and 15 is the number I had) I decided it was time.
I used 15 avocado skins and pits to dye 400g of yarn. After scooping out the tasty parts I scraped the skins clean with the spoon and rinsed everything in tap water. Some skins (about 4) were fresh that day, the others had been frozen for up to 1 month.
To extract the dye: I put the skins in about 3.5 litres of water. The pits I chopped up in my food processor to icrease the surface area in hopes more dye would be extracted. I added this to my pot and brought the whole thing just to a boil, then reduced heat to a simmer for 1 hour, stirring ocasionally. Then I let the pot rest and cool for 24 hours. I strained out the liquid and had 3 litres of dye solution. Note to self, invest in a fine mesh strainer for dyeing.
Yarn: 4 skeins of 75% superwash wool, 25% nylon sock weight yarn, bought online here.
Skein 1 and 2.
I soaked my yarn in water overnight. I poured half of my dye solution into my pot (I use a large enameled one bought on amazon, the porceline enamel surface is non reactive and this pot was cheeper than similar size stainless steel ones). And added an extra 3 litres of water. In to the pot went skeins of presoaked but not otherwise treated yarn. I brout the temperature up to just under a boil, reduced heat and simmered for 1 hour.
Skein 1: No mordant.
You'll see the without any help at all, avocado dyes wool to a lovely pale blush.Apparently if you keep skins and pits separate they'll give slightly different shades, and again, you can intensify colours by creating a more concentrated dye stock (ie use way more avocados), but this pale colour is very pretty in of itself, and the yarn was beautifully soft. No colour washed away with rinsing.
After removing skein 1 from the pot I pulled skein 2 out and hung it above the pot (did not rinse, just got it out of the water). My dye bath was still hot, I added in 1/4 tsp of ferrous sulfate powder (Iron mordant purchased from Dharma Trading Co.) and stirred it into solution. Then I lowered my skein quickly back into the pot. Bam! The colour change was mediate, with the skein darkening to a silvery purple. The trick with an iron bath is that it is non-reversible and the colour progresses with time. I should have started with even less than 1 tsp, but alas, that's why this is a dye experiment. But after two minutes the skein had deepened to a great silvery purple and I quickly pulled it out and rinsed it off., not wanting it to darken too far.
There still seemed to be quite a bit of dye in my pot, so I ran downstairs, grabbed another skein of 100% merino (100g DK weight) and threw it into the pot as is (dry!). You can see that skein (the bottom one) is lighter in colour than the first skein in that pot, showing that the dye pot is exhausting. If I had unlimited time and yarn, I would have dyed a full gradient until the pot fully exhausted (one day...).
I cleaned my pot (scrub really well, the tiniest leftover iron residue can affect your colours) and got ready for Alum.
Skeins 3 and 4
These skeins needed pre-mordanting with alum. Into my pot went 4 litres of water and 2 tsp of aluminum sulfate (Alum, Jacquard brand purchased on Amazon). I added my two skeins, which had previously soaked for 1 hour in water in my sink, and heated the pot to just under a boil, then reduced heat and simmered for 1 hour. I let the pot cool and sit overnight before removing the yarn (but not rinsing it).
Skein 3: Alum premordanted
I added the second half of my dye solution to my pot, along with an extra 3 litres of water. Into the pot went my two premordanted with alum skeins of yarn. I brought the whole thing up to just below a boil, reduced the heat and let simmer for 1 hour (I know same old same old). Then I pulled out one skein, the colour in this premordanted skein was nearly identical to skein 1 above. The major difference however was that the alum treatment left the yarn feeling crunchy. This is why it is recommended by many natural dyers that you include some cream of tartar (tartaric acid) to your pot when mordanting with alum, as the acidic pH helps to keep the wool nice and soft. Interesting that this didn't happen in my previous onion skin dying experiments. I may do an acid treatment on this skein and see if if helps to soften it up, since the texture, while not totally horrible, isn't as desirable as the softness of this skein originally.
Skein 4: Alum premordanted and Iron afterbath.
Just like before, I pulled my fourth skein out of the still hot pot and hung it out of the way. I added 1/4 tsp of iron to the pot. Stirred it up and then lowered my skein back into it all at once. Again the colour began to change imediately and although not nearly as dark despite using the same amount of iron (perhaps an effect of the alum treatment). This time I let it simmer for about 10 minutes before pulling the skein. Its concrete grey, not as deep as skein 2 above and without the purple cast.
So there they are, four beautiful skeins, four truly distinct colours, from one batch of avocado dye.