When you wash with my handmade soap there is a thin layer of glycerine left behind which draws moisture from the air onto your skin to keep it hydrated and prevent dryness. This isn’t the case with mass produced bar soaps where the glycerine is usually removed and reused in other products such as moisturisers.
Smelleez soaps all have a high glycerine content and glycerine is a humectant, that is a substance that readily absorbs moisture from its surroundings.
If you left a cup of glycerine out in a humid room, it would absorb water from the air until it was about 20% water.
When bar soap with a high glycerine content is stored in damp conditions, the glycerine in the soap draws moisture out of the air and onto the soap which then appears as little beads of water on your soap bar, just like morning dew on blades of grass! At first, this can look like frost but if you look closely, you can see hundreds of tiny little water droplets covering the surface of the bar.
This is sometimes referred to as soap sweating (yuck!) but the other name for this phenomenon is glycerin dew – which certainly sounds better!
So the dew is actually moisture from the air that the glycerine attracts, not moisture coming from inside the soap – it’s not melting! The more humid and damp the environment that the soap is stored in, the more likely you are to see this phenomenon. Glycerine dew doesn’t affect your soap’s ability to clean, it shows that it is doing the job intended – attracting moisture!
Now this phenomenon might be fabulous for your skin but it has created problems for me when it comes to wrapping my soaps. Living in Scotland, there is often quite a bit of moisture in the air – I’m not complaining it’s what shaped our landscape and made this such a beautiful place to live! But it does mean that when I go to outdoor markets and festivals there’s a pretty good chance that there will be some moisture in the air!
Glycerine dew is well-recognised and much talked about by soap-makers and, there seemed to be only one accepted solution - to wrap the bars tightly in plastic. Which is definitely not something I want to do! So over the last two years, I’ve been experimenting with different, more environmentally friendly options and for over a year I’ve been double wrapping my soap bars in compostable paper which has worked well for most situations. However, I’ve noticed that sometimes this is not enough to stop the glycerine from pulling moisture into the bars when they’re all wrapped up, especially if they're stored in humid conditions or if it’s a bit dreich which resulted in some of the wrapping becoming soggy round the edges. Although this doesn't affect how the soap bar works, it doesn't look very nice.
I’ve been using cellulose acetate to wrap my Rainbow Olive Oil Soaps for quite a while and this has proved the most effective way of preventing glycerine dew (and has the added benefit of letting people see their wonderful colours too!) Cellulose acetate is a natural, renewable, and eco-friendly material made from cellulose which is obtained from wood pulp or cotton linters (the hairy fibres that cling to cotton seeds after harvesting) combined with acetic acid which is the main constituent of vinegar. After it has been used the cellulose acetate biologically degrades to form carbon dioxide and water which nourishes plants and trees - so the lifecycle of cellulose acetate starts and ends in nature.
Therefore, I will be using this for all of my soaps going forward but your favourite bars will still look the same on the shelf as I’ll be keeping a single outer layer of compostable paper.