Does combining lye solution + oils at a higher temperature make for a harder bar of soap?

[SpaceCorgi94]

I remember the recipe for my very first bar of soap made instructing me to wait until the lye and oils were between 30-40C (86-104F)

This bar of soap ended up setting so hard, so quickly, that within just 36 hours it was flaking/crumbling around the edges as I cut it.

Since then I've used slight variations of this recipe, as well as other recipes entirely, however none of which have set quite as hard as this (even ones including saline, and a higher % of harder oils). One big difference is that after that first batch, I never bothered to have my lye/oils up to quite a high temp as 30-40C before combining them. Nowadays I always let them get to about room temp, as I like to prepare everything a day ahead so it's nice and laid out for me when it's showtime.

I'm wondering if this theory could be true. Do soaps made from a batter emulsified at a higher temperature set harder quicker than those at a lower temperature? Is this some magic of beginners luck I'm yet to rediscover? Or shall I ever be destined to chase the dragon?

Recipe in question: Back to Basics: Simple & Gentle Cold Process Soap - Soap Queen

 

[Anstarx]

It is possible. The heat can make saponification happens faster. My gelled soap are always faster to harden then my ungelled ones with the same recipe. Same reason a soap that goes into the mold in medium trace will harden faster then a soap goes into the mold at just emulsion.

 

[TheGecko]

I've soap at all different temperatures...from at low as 65F up to about 180F. Haven't really noticed all that much difference. Last weekend I made 5 batches of soap, at all room temperature all made within a hour, all put in the garage on the same shelves, all brought in the kitchen at the same time and all unmolded within 30 minutes. 1 batch was in a 6-cavity silicone mold, 2 were in 1lb silicone molds, 1 was in a 2lb silicone/wood mold, 1 was 2lbs in a 4lb silicone mold.

The soap in the cavity molds were slightly sticky. One of the 1lbs was slightly sticky, the other one popped out just fine. The 2lbs soaps slid right out of their molds. I cut all but the cavity mold soap...all fine.

 

[The Efficacious Gentleman]

To get the semantics out of the way, what would be considered "hard" bar of soap has more to do with the recipe and the cure than anything else. I think better wording is "does it make the soap solidify quicker?" - in which case yes, it can.

Saponification creates heat, and it also happens faster WITH heat. So if your batter is warmer or colder will mean that saponification will be faster or slower, all other things being equal.