More on Cream of Tartar

A quick update on Cream of Tartar - we have now heard back from Waitrose - their "Waitrose Cook's Ingredients" Cream of tartar is again Potassium Bitartrate.

I wonder where the "substitute" is going to eventually turn up! I also wonder WHAT it is, as I still haven't found anything!!

Cream of Tartar

So...........what does the name conjor up for you? For me it means the white powder that you buy in tubs from the bakery section of a Supermarket or Grocers store. I have no idea where the name "cream of tartar" comes from, but  historically, it was the "leys of wine" the powdery sediment found on the walls of wine cellar vats. Then it was given the name "Argol" and it could be red or white depending on the colour of the wine it came from!

 There appear to be many names for the chemical - the commonest I have found are Potassium Hydrogen Tartrate or Potassium Bitartrate, but you can also find monopotassium tartrate, potassium acid tartrate,

[R-(R*,R*)]-2,3 Dihydroxybutanedioic Acid Monopotassium Salt, Potassium (2R,3R)-3-carboxy-2,3-dihydroxypropanoate, and more.......!

The chemical formula can be written KC₄H₅O₆ 

or even

C4H4O4 (OH) (OK)

Its CAS  number is 868-14-4 (One of the commonest classifications to stop confusion between chemicals)

CB number -CB7854493

formula weight:188.18
E number - E-336(i)

  It is the mineral acid salt of Tartaric Acid and probably best known for its stabilizing properties when making meringues. It is a component in Baking Powder and also a chemical buffer.

So I can now see you wondering what this post is all about!

Many dye recipes both historical and modern recommend the use of Argol  or Cream of Tartar as an addition to alum in the mordanting process, it is there to assist the alum in mordanting wool with salts of Aluminium, Chromium, Iron, Copper and Tin. It is said to improve the permanence, fulness nad brilliance of the ultimate colour. For the chemists amongst you this is surmised to be due to the double decomposition of the tartrate and the mordanting salt, the mineral acid of the latter combining with the potassium of the tartrate and the metallic hydrate with tartaric acid, (it is also possible that a double salt is formed).

Given all the above information I am struggling to understand why several dye retailers in the UK make a claim that the Cream of Tartar sold for catering is a substitute chemical not suitable for use as the mordant assistant.

So what is this substitute? I cannot find it - is it the same product but using one of its other names?

For my own peace of mind I have comtacted Dr Oetker and Tesco both of whom are very clear that the product they sell under the name Cream of Tartar is CAS number 868-14-4 Potassium Hydrogen Tartrate (etc, etc) I have their replies in email format so if you wish to see them I am happy to forward on - or feel free to contact them yourself.

I feel so strongly that we should be able to buy the product we want under the name that it is known by that I would like to find out more on the subject of this "substitute" used for catering. Maybe if there is a substitute we should be considering approaching Trading Standards to get the name used as it should be and another name for the alternative!

What can have coloured my silk?

I have just prepared a variety of silk fibres and yarns ready for dyeing. There are several winter markets coming up so I thought I ought to get started - but without the usual panic and rush!

Maybe this was a bad idea! ALL the fibres and yarns were Mulberry silk so white rather than cream or caramel coloured. I scoured them all first - but in separate pans as I didn't want the fibres attaching themselves to the yarns.

 I had already mordanted alpaca and romney so the mordant was an exhaust bath being re-used, it had had alum and cream of tartar in (hopefully taken up by the wooly yarns) so I added a different proportion of alum and cream of tartar for the silks. The liquid was CLEAR, absolutely no sign of any colour before I entered the silk. The silk was still white before being entered.

The liquid was heated to about 45 degrees and then left for a day - I like the mordant to have a good length of time with the fibres! When I took the lid off to srain out ready to use again I had something of a shock! 

All the fibres had changed colour to a lovely shade of peach! The liquid has remained colourless - hopefully you can see that from the yarn picture. The mordant bath is stainless steel and there is nothing unusual about the alpaca and romney that came out before. (The green you can see is the tags I use for labelling my yarns - and no, none of the ink has come off either!)) I am sure there is no iron contamination and although I do sometimes add in tannin when mordanting silk (correct historically) there was none present here.

The white tub shows the silk caps that have been taken out of the bath - they really are very pretty, but what can be the colour?

I haven't yet tried to dye any of the fibres - that will be the next interesting challenge,

Has anyone had a similar experience - or any suggestions? I'll let you know how I get on with the dyeing in due course!