I haven’t used onion skins in the dyepot for several years, although I still always save them, and I keep the red onion skins separately from the brown ones, as they often give slightly different shades in the dyepot. Whilst rummaging through some of the boxes in my workshop recently, I unearthed several bags of onion skins, so last week I decided to use some of them to dye some skeins of wool.
Onion skins will dye quite readily without the use of a mordant but for the strongest, most vivid colours I use an alum mordant. However, if you use unmordanted fibres, the use of an alkaline modifier after dyeing will increase the depth and brilliance of the shades. For very deep colours you may need to use 100% weight of onion skins to weight of fibres, but I usually find that 50% gives sufficient depth and brilliance.
Colours on wool from brown onion skins
I started off by using some brown onion skins. The above photo shows, from left to right: Alum mordant, alum + iron and, from the exhaust dyebath, alum mordant, alum + iron
I then made a dyebath using some red onion skins. In the past, I have sometimes achieved interesting green colours from red onion skins but this time the colours obtained were not as bright as I had hoped they would be, probably because I only had a handful of skins. The photo below shows from left to right: alum mordant, alum mordant + alkali, alum mordant + iron, no mordant, no mordant + alkali.
Colours on wool from red onion skins
Afterwards, I wondered why it had taken me so long to get round to dyeing with onion skins again, as they really do give lovely colours, even if their light-fastness is limited.