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What is Crocking? Why does it happen?

Hello everyone! It’s a spring Monday morning here in Nashville, a little bit chilly, but not too bad. After doing a few trade shows recently, I wanted to make sure to take a minute to tell everyone about something somewhat unique to natural dyes. It’s called CROCKING. 

If you’ve worked with indigo before, you likely have already encountered this phenomenon. Basically, crocking is when dye color rubs off (or bleeds) after the item has finished dyeing. You may be working on a project with a beautiful, dark indigo, logwood or cochineal, then look down to notice that your hands have changed color! This can be somewhat disconcerting and you might think something has gone terribly wrong, but don’t worry! Natural dyes, in their deepest shades, even when washed several times by the dyer, will probably still have this crocking effect. It will go away after time, and is not harmful or an indication of any problems with the product itself. It simply means you are working with natural dyes! 

So here’s a bit of the science-y part of why: Natural dyes are fixed to the fibers with something called a mordant. There is a whole big scientific reason behind this, but basically, the short version, is that the mordant helps the fibers open up to allow the color to come in. Crocking happens when the dye process has stopped, but some of the color wasn’t able to adhere to the fibers with the mordant. With my Nutmeg Fibers, I wash and rinse them 3x before drying, to reduce the amount of crocking that might happen on the customers end, but even so, with certain dark colorways, and the amount of dye that it takes to achieve those, there will always still be some particles of dye that are “floating” on the top of the wool. 

There are a few ways you can fix this! 

1: You can wash your fibers before working with them in a bath of Euclan wool wash and warm water. Very gently agitate the fibers, so that you don’t accidentally felt any of them! Rinse the fibers until water runs out clear. 

2: When you are finished with your project and ready to block it, you can set the colors with a vinegar rinse, to further aid in setting in colors. To do this, simply follow this recipe: 

  • Add 2 cups distilled white vinegar to a wash basin filled with room temperature water, or your clean sink

  • Fully submerge your project in the vinegar bath, taking care not to agitate the fibers too much

  • Let it sit for 30 minutess to 1 hour, then drain the vinegar water out of the basin

  • Wash and rinse your project as usual, with a gentle wool wash such as Euclan, to help rid the project of the vinegar smell

  • Block and dry as usual

I hope this helps answer some questions you might have had about why certain dyes tend to rub off on your hands, or “crock”. Happy knitting everyone! 


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