Learning to Make Soap: Part 15

Jun 24, 2021

To finally answer the question of to gel or not to gel...

Today I thought I would revisit natural colourants and show you what the soaps look like after they have cured - have the colours faded or changed at all. And, most importantly, does forcing the soaps through gel really make a difference?

Just to remind you what I was testing - firstly I was looking at whether or not it was better to infuse olive oil with the natural colourants and then use the infused oil to colour the soaps or to use the botanicals directly in the soap batter. Secondly, I was testing what effect forcing the soaps through gel phase had - did it make the colours brighter? Did they last longer?

Ok so first things first - should I infuse the oils with the natural colourants or could I just add them directly to the soap? Personally I was hoping the answer would be I could use the colourants directly, because this would make colouring my soaps a lot less time consuming.

Of the colourants I have tested the ones that could be added directly to the soap batter were activated charcoal (grey), nettle powder (green), spirulina powder (green) and madder root powder (pink). In Learning to Make Soap: Part 12, you can see the soaps coloured using these botanicals just after unmoulding, but how did they fair 7 weeks later? Well as you can see from the picture below both the spirulina and the nettle have turned more brown over the curing time compared to when they were first unmoulded - but they are still quite a strong colour (although not really green, which was what I was looking for!). The activated charcoal still looks a dark grey and definitely could be added directly to the soap batter as it holds its colour nicely. The madder root is interesting because the colour still looks very vivid but the colour has definitely become a bit more peachy rather than pink.

Ok, so now lets look at the infused oils and see how they faired. If we compare the photo taken after 1 week to the photo taken after 7 weeks you can see that the colours have faded a little more by 7 weeks. I do quite like the pastel colours but the spirulina has faded the most dramatically - it almost looks like the soap hasn't been coloured.

So for a direct comparison between the soaps that were coloured using infused oils to those where the botanicals were added directly into the soap batter we can look at the spirulina and the madder root soaps. You can clearly see that the colours are much darker when the botanicals are added directly to the soaps compared to using infused oils. The green colour made using spirulina infused oil really is very pale and not all that colour fast. However, the green colour has turned to a green-brown when spirulina is used directly in the soap. So neither of these are ideal. For the madder root - again the soap where it has been added directly to the soap batter is definitely darker, but you can see the colour is more even when the infused oil is used - although it really has faded - but to a lovely pastel pink.

The final piece of the puzzle is regarding whether there is a benefit to gelling the soaps. In Learning to Make Soap: Part 13 I made a layered soap using infused oils (madder, alkanet, spirulina and annatto) that had been forced through gel phase. In the picture below you can see the soap at unmoulding and over 5 weeks later. Both the alkanet and the madder layer still look really bright, the annatto layer may have faded a little and the spirulina, as with all the other soaps has faded too but not as much as the other soaps.

If we now compare the layered soap (gelled) to the cupcakes (not gelled) you can really see the effect of gelling the soap - particularly for the madder root and the alkanet root. Both are darker and brighter and the colours seem to be pretty stable in the layered soap. The differences between the gelled and non gelled annatto and spirulina are a little more subtle - the gelled colours are brighter but not as striking as the madder and the alkanet. Having said that I do really like the more subtle pastel colours, but I think from a colour fast point of view gelling the soaps is the better option.

So it looks like I will still have to continue to make oil infusions for alkanet, annatto and madder root. However, the activated charcoal can definitely be added directly to the soaps and for a green soap I think I might still have to experiment a little to get the balance between the colour being stable and it going brown!

And in answer to the question to gel or not to gel, I think the answer is a yes, as gelling the soap helps ensure the colours are bright and have staying power!

That's all for today - I am off to make what hopefully will be the final designs for my first Small Kindness Core soap collection - very exciting!

Until next time


I am Kelly Townsend and this is the Small Kindness Blog. I am a scientist, a bee lover, a rewilding obsessive, and I want to spread Small Kindnesses through the medium of soap. Follow me on Facebook, Instagram and Twitter for your daily dose of kindness (as well as to see how the soap making is going!)