During the saponification process, why does sodium hydroxide produce a solid soap?

Answer 1

That occurs because the soaps, being salts, have a very high melting point, and are also much less soluble than sodium hydroxide. The result is that the triglycerides are broken down into free fatty acids and glycerol by the hydroxide and heat, and the negatively charged fatty acids associate with the sodium ions to form soaps, which precipitate out of solution as they form in the aqueous mix. The soaps do not melt at boiling water temperatures, and come out of solution as soon as the saturation point is reached...a foregone conclusion if enough reactants are provided.

Answer 2

The potassium salts of the fatty acids used to make soap have a lower melting point than the corresponding sodium salts.