Glycerin rivers don’t affect the quality of your soap, but they do affect its appearance. They create a cracked appearance that looks like tiny rivers.
How Do They happen?
When you make soap, glycerin occurs naturally as a by-product. It has great properties for soap making because it’s good for cleansing, and because it’s a humectant, so it attracts moisture to the skin, making your bars more hydrating. When cold process soap gets too hot the glycerin can congeal, which makes the rivers more noticeable. They can also make your soap softer if the rivers are thick or if they are all in one section of the soap.
Glycerin rivers occur more if you use pigments…
…especially titanium dioxide, because they’re more dense than micas and lab colours.
How To Prevent Glycerin Rivers
They don’t occur often but there are some tips for preventing them:
- Mix your colours well before adding them to your batter, especially if you’re using pigments. Use 1 teaspoon of colour in 1 tablespoon of a light weight oil like sweet almond or canola.
- Uses micas rather than pigments.
- Mix titanium dioxide with oil rather than water, as it disperses better. You can buy an oil specific version
- Buy micronized Titanium Dioxide as the particles are smaller and mix easier.
- Try water discounting by 10-20%. This also helps prevent soda ash formation, helps your soap to unmold sooner and to cure quicker.
- Soap at a lower temperature, or at room temperature
- Put the mold in the freezer for an hour or two and then move it to the fridge to keep it cool.
- Avoid any badly behaved fragrances, which can cause your soap to heat up.
Personally I don’t mind the rivers, as they add character to your soap, but many soap makers think they make your soap look less attractive, which can be a problem if you want to sell it. Try these tips and see if they help.