Monday, 9 May 2011

Michael Garcia Organic Indigo Vat Thoughts on Lime

I am getting more and more puzzled about this vat.
Michael Garcia  apparently used oyster shell to make his vat alkaline. Oyster shell s are 95% calcium Carbonate . When I asked him about this he said it was a joke! He  said he wanted to use mineral lime but was told nobody would think it was an organic vat. so he used crushed oyster shell, but he told us to use lime. Gardeners lime rather like Oyster shell is mostly calcium carbonate  and will only  make the vat mildly alkaline.  I have just made up a vat suing it and the vat is pH 7-8.  Builders lime on the other hand is what is known as slaked lime or calcium hydroxide and what is used in a zinc lime vat,. Michael Garcai  said to use lime as it was very active ( and technical formula h wrote down was calcium hydroxide) and the whole time at the back of my mind was the thought but how can oyster shells do this but the thought stayed at the back and never came to the front of my mind!  It is a long time since I did Chemistry!
Lime (apart form being a fruit) can mean:
Calcium Oxide- unslaked lime
Calcium hydroxide -slaked lime.
Fine but where do the oyster shells come in?


  1. I could be wrong but in order to get the shells to a "lime" state, you would have to heat it to drive off the Carbon and Oxygen (in the form of CO2).

  2. Hi Kelly I think without looking it up that this is calcining and the conversion happens at high temperatures in a lime kiln. hmm not what Michel Garcia was doing!
    I wonder when he said the oyster shells were a joke he meant just hat and was in fact using calcium hydroxide -slaked lime-and because it was all in French -although supposed to be a bilingual conference the demonstrations were not translated-I misunderstood. I think he must have been using slaked lime and will get some tomorrow as the formula for this is what he wrote down for us

  3. helen, thank you so much for these reports. I couldn't be there and this is the next best thing!

  4. Hmm - I have been pondering this, too, Helen. Calcium carbonate shells, oyster or chicken eggshell, would substitute for washing soda in a vat that uses ws as the alkaline. As usual, the only thing to do is try. Also interested to know if the vat came round in 45 minutes, which is what I have written down, and did you start your vat at 80C?

    I do hope the oystershells work - it will be an interesting experiment....

  5. Hi Jane no I did not I did not realise how high a temperature he started at but adding garden lime to the vat at 60 degreesc only made a low pH .I might try putting it in at 80 degrees C and see if it make any difference. however when I saw it it seemed to come into order very quickly and when he talked to Debbie, Ulrike and myself and gave us a recipe it was with calcium hydroxide.

  6. Is it just me that finds this kind of thing somewhat annoying? Either share or don't share but don't deliberately obfuscate! I know we all have to try things ourselves but it saves a lot of fruitless experimenting if you can eliminate that which definitely doesn't work and so increase the chances of success. Subsequent sharing of positive results can only advance the art and science of natural dyeing.

    Perhaps there's a translation problem involved here? Or we just aren't getting the "joke". M. Garcia's English is not great but it's certainly better than my French! I'm sure you'll let us know what happens with your vat, Helen.

  7. another thing that Michael Garcia asid was that it had to be lime as it must be very active and lime is very active ( he said) and wrote the formula for calcium hydroxide . It raised the pH rapidly he said. Well calcium carbonate is not going to raise the pH rapidly.
    Yes Louise like you Iam feeling quite annoyed about all this. I spemd a lot of money going to ISEND and the workshops and demonstrations were intensely frustrating as they were rarely possible to see or follow with any coherence.

  8. Well, so far no sign of any action at all in the oystershell vat! It is no longer 80C, after 24 hours, but will probably reach that in our south west, double glazed conservatory that is far too hot for normal people!!

    If he was joking about the oyster shells - though as they are calcium carbonate they might well work with patience, time and large quantities in a vat - then he should have been absolutely clear about that and ensured that someone with adequate translation skills made it clear to English speakers. Or any other non-native French speakers.

    Should we contact him and ask for clarification?!

  9. I agree Jane aim very cross about this. he did talk to three of us about it -when he told me it was a joke- and gave the t he chemical formula for his vat with a list of alkalis,including ammonia, and calcium hydroxide and another time told me that you had to use lime , and calcium hydroxide is of course referred to as slaked lime. How long did it you to grind the oyster shells.

  10. Well, quite a while - it was hard going, so I kept going back to it, then having a break. It was easy to break into small pieces, but a swine to grind and so tough I didn't want to use my coffee grinder (used for dye grinding!).

  11. I just took a class with Jay Rich who took an indigo class with Michel Garcia after ISEND. We used calcium hydroxide - pickling lime here in the US - I posted some of the results here -

  12. Many thanks Diane the link was very useful. Best wishes Helen

  13. at the demonstration Michel Garcia used "boiled oyster shells" that he crtushed really simple in his hands. So maybe the oyster shells develop the calcium hydroxide after being boiled (refering to Kelly's comment)

    I will definitely try the vat when I'll be back. Right now, everything is in a hurry. And that's no state for indigo

  14. Thanks Ulrike- I shall think on that and I agree with indigo is not something to be rushed.

  15. Michael Garcia is at Quilts 2011 in August and is leading a 3 day workshop on indigo dyeing... I've just signed up for it... you'll find the details here...

    so hopefully things will become clearer after these 3 days...

  16. Hi Tricia thank so much I have already booked!
    With regard to the vat I have worked it out in my head and plant now I have calcium hydroxide and fructose to do one on Monday after my big ( 6oth) birthday party!

  17. M. Garcia is also doing a lecture and a couple of workshops (including the indigo) this coming autumn at the Maiwa Symposium here in Vancouver, BC, Canada.

    I'm not sure yet whether I'll be able to take advantage of this opportunity. But Maiwa Symposium is a really fabulous series of events and I hope to catch at least a few of the lectures and exhibits. Another workshop for indigo-philes is Indigo Shibori with Akemi Nakano Cohn.

    BTW, a very Happy 60th Birthday, Helen! From one who reached that milestone half a year ago...

  18. I think burnt oyster shells are used as a pH booster on top of another lye such as rice straw ash-water or wood ash-water.. then it would be possible to raise the pH up to 11 or so. I am not sure it is possible to raise the pH to 11 with just oyster shell. But you could try adding lots! The shells do have to be burnt first .. it certainly helps with the grinding!

    I was a little late to Michel Garcia's demo I wondered if he had problems with the heating as I did at my demo, it certainly halved what I was going to do.
    I wondered why the small samples he was pulling out of the vat which apparently had 15gm of indigo in it were so weak.
    I would be interested to have some feedback from those going to his workshop in England.
    I would be very interested to make this work.. especially as it seems to be so quick.

  19. Thanks Louise and Andie
    I had a lovely birthday party folks although the British weather lived up to it's unpredictable reputation and gave us wind and rain so the guests ended up in the house-with a stalwart son cooking outside on the barbecue in the rain.

    As I understand burning oyster shells at a high heat produces calcium oxide which added to water gives calcium hydroxide but the temperature has to be high to burn hence the lime kilns.
    I always run indigo dyeing workshops here every August using all the different plants in the garden so I will add on the organic vat too in case anyone can get here. For anybody who is interested Manchester International airport is only an hour and a half away and this has been a successful way for some to get to my workshops.