Thursday, June 26, 2014

The day after

Here are a few photos of my fabrics oxidizing the morning after yesterday's big dyeing session:

Despite an eventful start, this round went really well.  The craziness came when I learned why you should always wash your stock solution jar after the end of a dyeing session.  I didn't bother, because I figured that glass is non-reactive, and the stuff left in the jar might be good for the next go-around.  But I had a real surprise yesterday, after I set my jar of stock solution in a bucket of warm water to reduce.  After about 45 minutes, I went to check how the stock was doing.  When I lifted the jar, the dye solution stayed behind in the bucket!  The solution just ate through the bottom of the glass and left the jar in two pieces.  I can only guess that the residue from the old dye stock weakened the bottom of the glass, and the new solution just put the jar out of its misery.

I had read that something like this could happen, but not really believed it.  Now I'm worried that the old solution that sits in my vat between sessions is going to eventually eat through it as well, since I also read that that can happen to stainless steel.  The pH in the vat is significantly lower than that of the stock solution, so the stuff in the vat shouldn't be nearly as corrosive, but even so, it's cause for concern.  I read that heavy-duty plastic garbage bins are stable long-term, so from now on, I'm going to try storing my exhausted solution in a garbage bucket in the back yard.

Meanwhile, the diluted stock solution in the bucket looked good, so I just bailed a gallon of old, exhausted dye from my vat and went ahead.  The vat might have been the best that I've made thus far: it seemed very lively, with a lot of bubbly flower.  Possibly it was a little overreduced at first, but by my second round of dipping, everything came out of the vat a beautiful bright kelly green, which I've come to think is the sign of a good vat.

I'll say more about the highlights of yesterday's session in future posts, after I've washed, rinsed, and ironed all of the fabrics.  The short story is that I'm really pleased: the nui shibori pieces came out beautifully, especially my two attempts at shirokage (white shadow) dyeing, and I also worked hard at manipulating my fabrics in the vat, in order to improve dye absorption.  I did have one other problem--bits of gritty gunk kept showing up on my fabrics.  Fortunately, it brushed off easily enough after the first round, but I'm not sure what it was.  Sludge, perhaps, left over at the bottom of the vat from the previous session?  Or was it related to the corroded glass from the stock jar?  Could it have been little bits of whatever you get after sodium hydroxide (lye) eats away stainless steel?  I think the first possibility is more likely, in which case I'm going to have to start putting some kind of grating or something in the vat, to keep fabrics from touching the bottom.  Storing the solution in another container and cleaning the vat between sessions should also prevent this problem.

The adventure continues!


  1. Holy crow, I heard indigo dying could be dangerous, but I am amazed that it ate through the jar! Live and learn. :)

    Everything on the rack looks really promising, with some dark rich colours, too. Looking forward to the next post!

  2. Very interesting! I've never used stock solution, mainly because I mainly dye silk and I'm worried about the effect of caustic soda, however dilute it is. I usually make up my vat the day before I'm planning to dye, to give the indigo 24 hours to reduce.

    But you got some lovely pieces from the vat, despite your eventful start! :-)

    1. That's interesting--I had wondered what would happen if one added the indigo directly into the vat. Are you using a zinc-lime vat? I've wondered about switching to zinc and keeping a big vat sitting in the back yard, but at least for now, I'll be sticking to thiox.

  3. I use sodium hydrosulphite (also known as sodium dithionite) as the reducing agent, plus salt, washing soda and of course indigo - and I add them directly to the vat, stir, and leave at least overnight. When the colour starts to become less intense I try adding more washing soda and/or hydro first before adding more indigo.

    My vat is a plastic bucket, which hasn't dissolved yet. ;-)