Updated: Aug 25, 2020
When I cut our latest batches of our coffee soap (which is my personal favorite - cocoa butter, mmmmm) they had glycerin rivers in them! The white, lacy lines going through the soap are called glycerin rivers and are caused by the soap heating up. All of our soaps go through 'gel phase' which is part of the saponification process where all of the fats used combine with the lye to - well - make soap! Gel phase makes the soap harder and the colors more intense, also.
Although we do not use colorants in this particular soap recipe, some colorants can also promote those lacy cracklings that you see.
Glycerin occurs naturally in soap, being considered a byproduct. Many large manufacturers actually remove the glycerin from their soap to sell separately. I think it just makes their soap more drying to my skin.
The soap is still safe to use and the crackling does not affect the final product, other than offering a visual appeal!
Have a great day!