ozone & indigo

Recently, in the workshop at the Japanese American National Museum one of the participants brought some fabric that she had dyed in another workshop somewhere.  It had faded radically and even more so along the folds and creases.  She wanted to know what had happened.
This is something that also came up a couple of times in the online indigo workshop and was struggled with over there.  Occasionally, I have seen it in my own indigo dyed pieces and strive to do those things which I find help to alleviate the problem.
As far as I have been able to understand, and the experiences I have had with this type of fading have led me to the following understandings.  Please feel free to jump in here and correct , inform and add to our knowledge on this for other folks as well.
The issue:
-fading of the fabric along exposed areas and folds where the cloth is exposed to air and or humidity. I have even seen fade lines on indigo cloth that I have hung (flat) to dry outside overnight that had a bit of a sway in the hung cloth. It seemed that in this case the overnight humidity was the over-riding factor.


three shades from the fermentation vat ready to assemble into the cloth packs for the shop

What is happening?
– ozone in the atmosphere is reacting to the cloth and any chemicals left in the fabric and additionally with UV light to produce an oxidizing effect. Smog and humidity also figure into the mix even in cloth that is well washed out.

At first, I thought that only fabrics dyed in a chemical vat or a pre-reduced indigo vat were susceptible to this.  Not true.  They may be MORE prone to it but fermentation vat dyed indigo is also affected.

What to do to minimize this?
– wash out your fabrics well before dyeing to remove any chemical treatments.
-build up your depth of shade over many dips in the vat. Have a light vat and a dark vat to produce various shades of blue through repeated dips and really work the dye into the cloth.
-rinse your indigo dyed cloth well between dips into the vat and then finally wash them well with a good rinse in the end.  You may have seen photos of Japanese dyers planting their indigo dyed cloths along a river or stream to let the water run through- this would definitely do it!  Getting out any chemicals that can react to the ozone is beneficial.
-once dried and ready for storage until use, you can keep your indigo cloth in a drawer or wrapped in a towel to keep the edges from fading.

Finished pieces (such as a quilt on a bed, a pillow, a wall hanging) will fade more evenly and possibly without notice as they are more evenly exposed to the atmosphere. All indigo will fade with use (think denim).  Well dyed dark shades built up by many dips seem less susceptible.   This is one reason I prefer the fermentation vat over the pre-reduced or chemical vat-more work but a more satisfying process and result. Also, be aware that different fabrics will fade differently. Think about the weave and the fiber.

There are even products out now for commercial dye houses that speed indigo fading (ozone finishing!) with the use of ozone related treatments said to be less labor and water intensive. Consulting companies work with manufacturers to troubleshoot their process and diminish the fading (or even speed it up!).

What if it’s not a problem at all?  It’s a matter of perspective.


Yesterday’s moon- on an open weave linen


15 thoughts on “ozone & indigo

  1. Kim Nelson

    I did much research, with few definitive results regarding ozone fading. I have a shop, Raina’s Textile House in Berkeley, CA and realty didn’t want someone to open s beautiful
    Tablecloth and find it yellowed all along the edges, etc.! The closer items were to the door- and smog, the worse it was. I have also found that this ozone fading happens more with vats that use lime.
    The best remedy I have found is to be sure to return everything to neutral PH- wash with neutral soap (Dawn) and soak in a vinegar bath.


    1. shiborigirl Post author

      and I would imagine the relative humidity in Berkeley doesn’t help much. With local tap water here at around 7.5-8.5pH I prefer a good clear water wash in the end.


  2. Suzanne Connors

    I have also had this happen in my studio. I am in South Florida and there is extreme humidity here. It is important to neutralize the PH and rinse well. Longer dips and multiple. I have even started boiling after. I have had items fade after hanging in the shop, items on silk have completely faded away and I no longer use indigo on silk fibers. How did the ancients keep the indigo on the beautiful silk kimono fabrics?
    I too thought this was a result of pre-reduced indigo, but I have had the same results with synthetic and natural indigo. I sell my products so this is a huge concern!
    In a recent workshop with Catharine Ellis, we treated our indigo with soy post rinse. I plan to try this with my next dye batch. I also was told to do this by John Marshall. Have you used soy?


    1. shiborigirl Post author

      no, I don’t use the soy technique as with one wash-poof! maybe fine for finished display pieces. silk fabrics (especially vintage) seem to suffer more I’ve noticed. I’ve often wondered if the camphor balls used in storage had an effect.


  3. nemo-ignorat

    I found that storing (letting it rest/mature) the dyed fabric after dyeing, washing and drying in a cool shady place for quite a long time (I tend to let them lie for weeks or even months), helps a lot with fading (or better to prevent it). As does a slow build up of colour. To get dark blues I dip up to 15 times. (Except for katazome resisted fabric. With nori zome I use a stronger vat and only up to 5 dips depending on the quality of the nori.) And as you I rinse after every dip to remove excess pigment on the fabric.
    Since I dye mostly cotton and linen, I store my fabrics rolled up not folded in a nice case. Linen tends to break on the folds. Especially the fine linen I sometimes use.
    I mainly use a simple hydrosulfite vat with calcium hydroxide. And I tend to dye rather cool.

    There is a difference though when I dye protein fibre. It seems that protein fibre keeps the dye better when I use the same vat but warm (around 45 deg C) Somewhat lower pH (for cotton I sye in a range between 11.5 – 12 protein fibre pH 10 – 11). Again, short dips and as many as I need to get the shade I want.
    I let all my naturally dyed fabrics and yarns mature in a dark, cool place and I found it most helpful concerning fastness.

    Liked by 1 person

  4. jude

    I remember when I worked in the textile industry, garments were treated with an ozone inhibitor , still I remember it continued to be a problem for retailers when things stayed on the shelves too long. it’s the nature of the thing and I have come to love it.

    Liked by 1 person

    1. shiborigirl Post author

      isn’t it funny how at one time an ozone inhibitor- and another time ozone finishing! the nature of it.
      i seem to remember some time back we were both playing with ozone fading as an agent of pattern. will do that again to post an example.


  5. Lynn D

    Have just reawakened old indigo fermentation vat. Recall instructor saying same thing, keep indigo dyed items stored in dark. Sounds lik same way blue prints are treated. My vat hasnt turned green after 2 weeks (sun day,house night), but it dyed blue that didnt wash out. Will try feeding more or adding more ash water (dont have pH meter or strips). Forget best ways to wash to keep color longer.


      1. Lynn D

        Never any green, 1 time very edge greenish. First try an instant teal blue on wool yarn. Usually try cotton. Does seem to work differently with cotton, silk and wool.
        Last night put a little bit of the vat in cups to try see if needed more reduction or alkalinity. Adding more cooked fruit liquid to 2 cups, more ash water to 1 of those and another cup, even rice bran, madder root, baking soda (that turned grey). None dye green first, most leave a pale blue. WIll try several dips and then wash.



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