DIY Vanilla Colour Stabiliser for MP Soap

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I’ve been searching for an alternative to the VCS (vanilla colour stabiliser) I’ve been reselling for years now and after finding this article, it turns out the solution is local, cheap and readily available. Thanks to ultimatehpsoap for sharing this wonderful info giving her permission for me to use the formula she presents.

If you’re not interested in the details and just want to see the the recipe that I used and the results, you can skip to the bottom.

I have tested the formula from the article using a soap base that I know discolours quickly as well as a fragrance with a high vanilla content and the results are quite surprising. I’ll share them at the end of the article.

Sodium Thiosulphate (‘hypo’)

I purchased 1kg of sodium thiosulphate (aka sodium thiosulfate) online here and then delved a little deeper using Wikipedia, where I learned that it is often referred to as ‘hypo’ which is much more practical so I’ll be using this name from now on.

I also wanted to find out:

  • Why is 25% (weight) hypo solution the right amount?
  • What would the shelf-life of my hypo solution be?

Why 25%?

To answer the first question, I took a look at the TDS (typical data analysis) for Stephenson’s Crystal Vanilla Colour Stable base that I found on the web. It lists sodium thiosulfate as an ingredient (yes, we are on the right track!).

It’s concentration levels are 0.1-0.5%. I am assuming this is a weight percent.

So, if I am using 1000g of soap, 3% fragrance and therefore 1.5% (25%) hypo solution, I will have this much hypo in my finished soap:

.015*.25*1000 = 3.75g

This is .375% (3.75g/1000g) which is in the range Stephenson uses.

Could I Use More than 25%? 50%?

You can make a stronger solution so that you add less to your base, but solubility depends on temperature. Again, from Wikipedia, you can dissolve:

70.1 g/100 mL (20 °C)
231 g/100 mL (100 °C) <- not too useful to us, but it gives us an idea of the upper limit!

This tells me two things:

  1. 25g is going to completely dissolve in 75g of water in most climates with no issues.
  2. 50g/50% should be fine unless it’s really cold.
  3. Not to store my solution in the fridge, otherwise some of the crystals may condense in the bottom of the container and you’ll need to wait for it to return to room temperature before they dissolve again.


I did some research into how chemists prepared and stored their hypo solutions for Stoichiometry experiments. Apparently there is an airborne bacteria that consumes sulphur and will reduce your solution’s efficacy if left open to the air or even if not prepared properly. This put a damper on the idea of master-batching or even short-term storage for me.

You should boil your distilled water (in fact, double-boiling is even better). I prefer to prepare the solution as I need it and use it straight away, disposing of the rest.

The crystals should be stored between 10-25 degrees celsius for up to 18 months from the manufacturing date.

How Far Will 1kg Go?

If you’re only using 100g of solution at at a time, that’s just 25g of hypo which is actually quite reasonable ($18*.025 = 45c) considering you don’t need to worry about storing a solution that may grow mould/fungi.

1 x 1kg bag will make you 40 (1000/25) large batches of soap (100g of solution should cover 6kg in one go). Alternatively, do a half-batch of hypo solution to make it go even further.

The Recipe I Used

[cooked-timer minutes=”5″]5 Minutes[/cooked-timer]

[cooked-recipe id=”80824″]

MP Soap Test Results…

I used 3% fragrance oil in all four soaps and 1.5% of 25% hypo solution in only the top two soaps pictured. These results are after just 24 hours. The base used was Stephenson Crystal Aloe and the fragrance was Bayside Soap Vanilla Peach which I will be introducing this month.


Your MP, CP or HP Soap Test Results…

Has anyone given this a go? I would love to hear your results… leave a comment below 🙂


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