Not all yellows were created equal; some are lovely light fast, others more fugitive. There is warm yellow, sunny yellow, greenish yellow, pale yellow... the possibility are endless. I decided to test the very best of the bunch for you. Besides pomegranate and myrobalan (being substantive dyes), all yellow dyes will need a good mordant base to stick well to your fabric and improve light- and wash fastness. These are what we call adjective dyes.
For this experiment I used organic wool and Khadi cotton, both were mordanted with 15% WOF aluminium acetate in a hot mordant process (you could use also aluminium formate in a cold process or other aluminium based mordants to read about here).
The fabric was left in the mordant water overnight, and rinsed. I used it while still wet (you can keep mordanted fabrics moist, in a plastic bag in the fridge for 48 hours if you know you will use it).
The following dyes were used;
1- Name Marigold
Latin Name Tagetes sp.
2- Name Weld
Latin Name Reseda Luteola
3- Name Dyer's Greenweed
Latin Name Genista Tinctoria
4- Name St. Johnsworth
Latin Name Hypericum perforatum
5- Name Goldenrod
Latin Name Solidago virgaurea
6- Name Myrobalan
Latin Name Terminalia Chebula
7- Name Pomegranate
Latin Name Punica Granatum
The dyes were all used at 50% WOF. I had to dye in two batches because I do not have seven different pots to do this in. Fabric and dye stuff were heated together to below a simmer for around one hour, left to cool down in the dye pot. Chalk was added for neutralising the dye bath, and getting better results on your yellows, see here why. There are no specific WOF's for this, just use a spoon in the bath. None of the dye stuffs was soaked before dyeing.
I only used the raw dye materials, it would not be fair to compare 50% weld extract with 50% cut dyer's greenweed.
Results, all samples dried, washed , dried and ironed.
1 Marigold. 2 Weld. 3 Dyers' Greenweed. 4 St. Johnswort. 5 Goldenrod. 6 Myrobalan. 7 Pomegranate rinds.
For some dyes it is so clear to see that they take better on cellulose or better on protein.
For example; Dyers' Greenweed (3) loves wool better than cotton. Myrobalan (6) is MUCH darker and coloured on the handwoven cotton than it is on wool, so we can learn from this that it has a greater affinity for cellulose than protein.
And now the important part no less; how much tannin is in the plant? Tannins reach with ferrous sulfate, so by dipping half of the fabric in a 1%WOF ferrous sulfate solution (we call this; post mordanting) we can see the fabric get darker, or not so much. The darker the fabric in reaction to ferrous sulfate, the more tannin it contains.
Why is this important? Because when you are eco printing with previously dyed fabrics, and you wish to incorporate an iron blanket, it will influence how your background will look. If you want to learn more about the reactions of tannins and ferrous sulfate, read this blog.
Side by side on handwoven cotton. Left with iron, right without iron.
Now I know that for manipulating my fabric to a nice moss green, I would choose weld. If I want my fabric to be black, I would choose Myrobalan. Dyers' Greenweed (3) stays the most yellow of all of them.
Side by side on wool. Different results!
The more I research, the more things I want to add to the 'to-do' list. I hope these little experiments will encourage you to do some research on the dyes you have at home.