Summer of Blue: First Attempt with Sig Vat (urine vat)

Updated: Jul 18

July 10th 2022

Met Rita at Waterloo Park to collect some woad( read more about woad from Susan & Ashley blog) for our first urine experiment. I first met Rita in early July and immediately felt we had a similar vibe. We decided to make an indigo vat out of urine at the second meeting.

Although it may appear absurd, urine vat is considered an ancient method of producing traditional indigo vat. It is also known as the 'Sig vat.

Oxford English Dictionary: Also seg, sigg, zig(g). Of obscure origin, the form does not correspond to older Flem. seyck, G. seiche, in the same sense. Urine


Rita and I went straight to her house after harvesting the leaves and began the vat process right away.



Because the indigo pigment degrades as soon as the leaves are picked, Rita managed to bring a pan of water to a boil before picking the leaves. We harvested 350g in total, which we quickly rinsed to remove any dirt before adding to the vat of hot water.





After 45-60 minutes in hot water, we could see that the blue indigotin had been released. When I was working with my Indigo Tinctoria, the blue extraction from the leaf took at least 24-48 hours. And now working with woad, I learn that different species of Indigo extract blue pigment differently...


Maintaining the proper temperature is critical when extracting the blue pigment.

The 'Fun' part

The next step will be somewhat of a trial process because this is our first time working with urine to make this indigo vat. Rita's first experiments were with woad and the cold/freezing technique, whereas I am very familiar with the Indigofera Tinctoria process. I used agricultural lime and fructose in my vat making, but I've never done anything with woad or urine. So we both agreed that this would undoubtedly be a trial-and-error experiment.


For my own record purpose:

+ 4ltr urine ( Dissolve agent )

+ boiled water to 50 celcius- add to the bucket

+ ammonia (alkaline substance)


Adding the urine

Aerating woad vat in a small bucket

Ph test - 10


We anticipated the production of foam in the bucket following the aeration operation. It appears to produce a good amount of foam, but Rita claims she read in another tutorial that it should have a slight blue tint. In my opinion, this might not have a favourable outcome. But at this point, the process cannot be stopped. We should be optimistic about the fact that the vet needs to take a week off while still being kept at a specific temperature to ensure the vat has the right amount of heat.


foam with slight blue tinge

Third meet-up on 18/7/2022

Rita and I met at Waterloo Park while watering the plants, and we sat down and discussed the vat outcome after a week of resting the vat.


Here's some of thoughts

Moving forward, we are going to continue again and this time we are going to try and feed the indigo vat with fructose and will then see the next outcome! Carpe Diem!

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