Soap Did Not Gel
I made a lovely batch of Lemongrass soap and it did not cure.
I believe it was because I did not have it hot enough.
Looking back I should have combined the lye and oils at 120 and it was more like 105(forgot it was not just coconut oil which is fine at a lower temperature).
Could I cure it by heating it up again in the oven?
I believe you are confusing the term 'gel' with the term 'cure'.
The term 'curing soap' refers to leaving the soap to sit for 4 - 6 weeks while the water content evaporates from the soap.
The term 'gelling soap' refers to the soap getting hot enough during the saponification process to turn to a semi liquid, gel like state and then to harden back up as it cools.
Soap does not have to gel to be used. In fact many people try to avoid the gel phase as they like the more pastel look of the soap better. Gelled soap produced darker more vibrant colours. Milk soaps are often not gelled so that they are whiter in appearance.
Whether or not you gel your soap is a personal preference and is fine either way.
Lye and oils do not need to be combined at such hot temperatures in order to gel either.
When I use the standard cold process method,
I combine my lye and oils at 90 degrees Fahrenheit and my soap still goes through the gel phase.
If you want to ensure your soap enters the gel phase, be sure your soap mold is not cold when you pour the soap base into it and wrap the soap in blankets to keep the heat in.
You can also place the wrapped soap onto a heating pad for 30 minutes to help the process along if needed.
There is no need to put the soap in the oven at this point since your soap is already made and cooled but you could hot process your soap if you want it ready for use sooner. There are a number of methods for doing this and I have a couple on my site.Rebatching SoapHot Process Rebatch
In the future you may want to try the cold process oven process method where the soap is placed in the oven at 150 - 170 degrees Fahrenheit for approximately one hour right after it has been poured into an oven proof soap mold.
After the hour, the oven is turned off and the soap is left to cool overnight. This method produces a soap that can be used faster than the standard cold process soap. A couple of weeks cure time is supposed to be sufficient.
Hope this clears up the confusion.
Good luck and happy soaping!