I am using stearic acid in a cp soap. I mix it in with my solid oils to melt it. It starts to melt at about 180 degrees and it starts to reform at about 170 degrees.
My question is can i mix this with lye solution at this tempture and still do it as a cp or do i need to mix this as a hot process soap?
I take it that pure stearic melts/reforms at the temps noted...
Heat your whole mix of oils to 180 to melt all together, including the stearic acid. Stir well & let it cool some. The stearic should remain dissolved in the oils solution. At some lower temp if stearic is other than a low percentage of the whole, it may start to precipitate out as it does in a cooling mass of palm oil (stearic is a sizable constituant of palm oil).
Generally, start your soapmaking process with the oils mix heated to just high enough to melt all the oils to clarity, together.
If the starting oils mix temperature is high, I'd start with the lye solution rather cool.
It's all Cold Process by definition as long as one doesn't add extra heat while the soap mass is being stirred & saponifying. The point to focus on is to have enough combined starting heat to kick off the saponification reaction & insulate your mold well (wrap with a doubled towel, over & under it & DON"T PEEK while it's finishing itself in the mold).
Soap Lore afficianados will say that the oils & lye solutions need to be at the same temp when starting, but really, it finds its own new combined temp as soon as you stir it together, so temp differences before mixing don't matter (I'll get chewed on for this statement, I'm sure).
If there's any risk to starting with 180 deg oils mix, it's that the combined, molded, wrapped up soap will get too hot & 'boil over' in the mold. That's not likely unless you are starting a very large batch at high temps (it might get quite hot in the center of the soap mass, then). For a small batch, the extra heat won't be a problem in the mold. It will, however, take your freshly mixing soap batter to trace & semi-solidity much faster.
What oils are you using?
You'll find that oil mixes containg sizable percentages of olive or especially of soybean oil take a longer time to trace & can benefit from higher combined starting temps.
We use a 6-oils (plus 2% stearic acid) mix here at SBM that goes to trace very quickly indeed, so we actually start our own soaps with the lye solution & the oils mix at room temperature, so we have time to work with it & pour it before it sets up. Then we cover the soap surface with Saran Wrap & put the whole wood mold into a special low-temp soap oven I made 10 years ago & let it 'cook' for 4 hours at between 120 & 160 degrees. Our oils mix starts out cloudy because it's not warmed to start (we stir it well), but it all melts quite well & goes to 'gel' stage in the soap oven, so I don't worry about the initial cloudiness at the start. You could say we use a "CPHP-in-oven" process. The results are perfectly consistent over hundreds of batches, but I did have to fiddle about with the process until I got it down right.
The bottom line is that this is a hobby of experimentation, so try it & take notes so you remember how it behaves!
I should also say not to take my advice or anyone else's as the only truth. Gather what advice & info you can from multiple sources and chart your own course...
Any one else have advice for Ronnie?