What is hot process I here you ask? Well it is a traditional method (likely ancient) of soap making which still includes combining a sodium hydroxide solution with your choice of triglycerides. But whereas, in cold process soap you add these ingredients together relatively cooled, in hot process the combined batter is cooked over a low and steady heat.
I use a slow cooker for this method (some just do it over the hob) as there is better control over the heat source. I think most soap makers who make the cold process method will have at the very least known of the hot process one and quite possibly might have tried it a few times in their soap learning journey. I knew of the process very well, having studied it when learning how to make my own soap. However, I didn’t actually make it until the start of this year when I made a few small test batches.
My first attempt was awful! I overcooked it, not recognising it had reached the ‘gel’ stage (and gone waaay beyond!). I think because it was a small batch it cooked quickly, literally within 15 minutes, but in my head I had the idea of hot process needing hours to be ready (this isn’t true – even my current big batches need less than 40 minutes max). Subsequent batches were much better and I loved playing around with colourants in hot process as the method gives a unique marbling effect which you don’t get in cold process. As I was testing a lot of fragrance oils for Miraj I did utilise this method a lot as some of the fragrances were known to trace or even seize the soap (in hot process the fragrance is added after the cook and as the lye for the most part has been neutralised, the fragrance doesn’t react with the soap and doesn’t trace – yippee!). Since this was for Miraj I used micas and OMG some of the effects with micas in hot process is just stunning! I wish I had taken more photos but as they were test batches it wasn’t on the top of my mind.
A positive with hot process is that when you add your superfat, you know for sure that it is the superfat and hasn’t saponified into the soap. In cold process, although we try our best and add the superfat after the soap has traced, there is no 100% guarantee that the oil you have chosen to superfat will remain unsaponified. With hot process there is as you are adding it after you have forced the saponification process to occur. That’s pretty relevant if you are using expensive cold pressed organic oils such as rosehip oil, seabuckthorn, carrot, jojoba, black seed etc.
Another positive is that it needs much less curing time compared to cold process which in my case needs a minimum of 6 weeks due to the high % of soft oils I have in my Olive Oil & Honey bars. HP, as it’s already cooked (and technically ready to use as soap), only needs 1-2 weeks in comparison. For quick turnover of stock, that is again a pretty important aspect.
However, until this year I was quite happy with my cold process method of making soap, as for me the process is much more therapeutic (barring trace accelerating fragrance oils of course). I enjoy the calm and process of mixing oils, additives and fragrance blends, then pouring the batter into my moulds, playing with the tops etc. But due to opening my Miraj company this year, I found for the first time that I had become very low on stock in my Etsy shop on some of the soaps from my main range – namely the Charcoal & Black Seed and Oats, Milk & Turmeric. Since both these soaps were in essence one solid colour I thought I would try the hot process method in order to restock quick.
I made my first ever big batch of hot process with my Charcoal & Black Seed recipe. A bestseller of mine, I like to always have it in stock. Despite my nerves at using all that organic oil in a method that I wouldn’t really call myself an expert at, I made it and was very impressed with the outcome and look. It has a marbled black on black appearance and is a nice firm bar. It stamped very well, when cut on the day after I made it (something which I can never do with cold process as the bars are still so soft). The organic cold pressed black seed oil was added after the cook so there is certainty that it wasn’t saponified within the oils and will impart its benefits when using the soap. The scent is more pronounced and slightly stronger, with a more pronounced anise/liquorice note which gets a little lost in the cold process version.
The scent aspect is something I also noticed when I made this again with Oats Milk Turmeric. After saponification the sweet orange note in OMT’s scent blend always gets dulled down and the obvious note becomes the geranium. But the citrus is definitely apparent in the hot process version of OMT as adding the essential oils after cook meant that the saponification process just didn’t get a chance to effect the orange oil (the high heat of saponification usually ‘burns’ away most of the notes of citrus oils such as orange, lemon, grapefruit etc). It is much more true to what I blend the fragrance oil to be in the beaker. Hot process would then be fantastic for those scents that smell great before soaping with but seem to morph into something unrecognisable after saponification. I don’t have a lot of these but still something to note.
But back to OMT in hot process version. It is simply stunning! I unfortunately didn’t have my camera working at the time but the process was amazing to watch. I had done my research on it and knew to add the turmeric after the cook otherwise it was prone to go a dark red shade. However, it still contained the red palm oil which took on the most beautiful hues while it gelled. Then when I added the turmeric, it did slightly redden but also started to take on that lovely marbling effect hot process has. I absolutely loved. If nothing else i know for sure that I will probably use the hot process method to make OMT from now on. The colour and scent alone justify it.