This is a fun question for me. I love the look and feel of a soap that has gone through a full gel phase, but have recently been experimenting with preventing gel.
So what is gel phase?
Simply put, it's when the finished soap batter heats up during the saponification process. The soap sort of "liquifies" during the gel phase before cooling back down and re-hardening. After this, the soap can be unmolded, cut into bars if necessary, and put away to cure for 4-6 weeks.
Several things can cause a soap to go into gel phase. Some fragrances or essential oils tend to make soaps more susceptible to gelling. I have personally found that spicy scents, such as cinnamon or clove cause my soaps to heat up. Floral scents also tend to move more quickly, leading to gel phase. Sometimes it's because the room we are soaping in has a higher ambient temperature than usual. This usually happens during the summer for me. It can also happen as a result of insulating your soap while it is in the mold.
Does this mean that gelling is a good thing? It's really personal preference. I find that gelling my soaps makes the colors really pop, which is nice. It also makes the soaps ready to unmold and cut faster, which is good for me because sometimes I'm just impatient. I want to see what's inside that loaf!
However, soaps that do not gel are also perfectly fine to use. They make take longer to finish the saponification process, which means that they may take longer to unmold and cut. The colors may be more muted. However, you may find that less fragrance and/or that delicate fragrances "stick" better in ungelled soap.
Which one is your favorite?