Catatan Asep

Double Boiler Hot Process Soap Making Method (DBHP) and Oven Hot Process Soap Making Method (OHP)

Posted on: March 14, 2007

Common instructions for Double Boiler Hot Process and Oven Hot Process Soap

Ingredients and amounts are the same as with Cold Process, with the following differences:

  • No matter how much water you choose to use for Cold Process soap, Hot Process requires a water ratio of 0.35-0.375 parts of water for each part of oils. The MMS saponification calculator gives the safest water amount for Hot Process soap.
  • Additives (including fragrances and essential oils) are always added at the end of the cook. “Luxury” oils are also added at the end of the cook if you want to protect their live qualities.
  • Cosmetic grade oxides and ultramarines must be added before cooking if you want to obtain a uniform color for the finished soap.
  • Milks, sugars and honey tend to burn when added before cooking, and will give brown to dark brown soaps. In general, recipes using milks, sugars or honey give best results with the Cold Process method.
  • Mixing temperatures are not crucial for the success of the soap, but it’s important to keep in mind that, if the soap mix is hotter than 50ºC (122ºF) at trace, the soap will most likely raise and “volcano” out of the pot during the cook.

Refer to the sections on soap safety and Cold Process soap for the initial step-by-step instructions.

Double check and make notes!

Saponification calculators, pen and paper are a soaper’s best friends. Whichever the source of your recipe, always run the amounts through a SAP calculator and make sure the amount of caustic soda is within the safety threshold (from 3% to 10% superfatting, 0% superfatting for laundry and cleaning soaps only).
Also…. don’t forget to make notes. Troubleshooting a problem batch is impossible, unless we know exactly what we did, how we did it and in which order. No notes also mean replicating a successful batch might be very difficult. So don’t be afraid… and write 🙂

Double Boiler Hot Process Soap Making Method (DBHP)

Special Tools

DBHP requires a double boiler setup. This can be arranged with any two pots, one larger than the other so that the smaller will fit inside the larger, leaving some space at the bottom and at the sides of the smaller pot.
The larger pot can be any metal; for the inside pot, choose stainless steel or heat-resistant glass.
A cake cooling rack is placed on the bottom of the larger pot, to prevent the bottom of the smaller pot to be in direct contact with the heat. An empty tin upturned and with a couple of holes punched in the bottom, or a rag, folded several times, can be used instead of the cake rack.

How to Proceed

  1. Prepare your double boiler, organize your workspace and have recipe, ingredients, tools and vinegar ready.
  2. Measure out (by weight) water and caustic soda, then prepare the lye solution and place it in the sink to cool down.
  3. Measure out fats and oils (by weight), and place them in the inside pot (referred to as “soap pot” from now on). If you wish to add some oils at the end of a cook, measure these out into a separate container.
  4. Place the rack, tin or rags on the bottom of the large container (referred to as “boiler” from now on).
  5. Add to the boiler enough water for the soap pot to be half-submerged, but still not floating.
  6. Place the soap pot inside the boiler and turn the heat on to medium.
  7. When the solid fats are melted, remove the soap pot, place it on your work bench and add the lye solution as described for Cold Process soap. Leave the boiler on the stove while you do this.
  8. At trace, place the soap pot into the boiler and replace both lids.
  9. When the water in the boiler starts boiling, turn the heat down and keep to a slow simmer (lids always on) for an hour.
  10. While the soap cooks, prepare your moulds and the ingredients you wish to add at the end of the cook. Remember you’ll have to work quickly with the cooked soap paste!
  11. When the soap has simmered for an hour, remove the lids and give the soap paste a stir. The soap should have a jelly-like look, with a consistency similar to applesauce and a nice golden-yellow color. Take a small amount of soap out of the pot and place it on a saucer for the “ball test”. Replace the lids.
  12. When the small amount of soap you have placed on the saucer has cooled down a bit, roll it between your fingers into a ball. If the ball keeps its shape, without being too sticky, and turns an opaque whitish color, then the soap is cooked.
  13. Depending on batch size and base oils/fats, Double Boiler soap needs cooking for 1 to 2 hours, with shorter times for smaller batches and recipes with a higher content of saturated fats, and 2 hours for larger batches and recipes containing high amounts of unsaturated fats. DBHP castile soap (olive oil only, or olive and castor oil) usually requires 2 hour cooking times.
  14. If the soap ball is sticky and doesn’t roll between your fingers, the soap needs cooking longer. Test it again after another 15 minutes.
  15. If the soap ball is crumbly, the soap has been either cooked too long, or the heat was too high during the cook, or maybe you have forgotten to replace the lids at some stage. The soap is going to be perfectly usable, but you might find it difficult to mould.
  16. Remember that the water in the boiler must simmer, and never boil too fast.
  17. When the soap paste is ready, turn the heat off and let the water in the boiler cool down to 50 to 60ºC (122 to 140ºF). You can now add the extra ingredients.
  18. If you keep the soap pot inside the boiler, the soap paste will remain soft longer, and adding the extra ingredients will be easier. Be extra careful when mixing, to avoid hot water splashes!
  19. When all the ingredients have been added and stirred in thoroughly, pour or scoop the soap into the prepared mould(s). Tap each mould to get rid of air pockets and ensure proper filling. Larger moulds might need “banging” on the work bench, and you might want to place a couple of rags between mould and bench to avoid damages.
  20. Place a piece of baking paper on the soap and press/smooth down with a clean spoon (or you can use your hands, if you are wearing rubber gloves).
  21. To obtain a smoother, finer looking soap, you can insulate the moulds as explained for Cold Process soap. The soap paste will cool down slower, and will settle down better in the mould.
  22. When the soap has cooled down, you can cut it or slice it before arranging on racks for the 4 weeks curing period. You can however test your soap straight away, because cooking insures that saponification is complete at the end of the cook.

Oven Hot Process Soap Making Method (OHP)

Special Tools

OHP requires one stainless steel pot, large enough to accommodate base oils and lye solution, while leaving at least 1/4 of the pot empty. It is best not to cover the pot with a lid.

How to Proceed

  1. Turn the oven on the lowest setting (or 100ºC – 212ºF at the maximum) while you prepare ingredients and tools.
  2. Prepare your soap mix as described for Cold Process soap.
  3. When soap is at trace, place the pot in the oven and cook for 10 to 20 minutes, depending on batch size and ingredients.
  4. Turn the oven off and leave the soap pot in (door always shut) for approximately 1 hour.
  5. After this time, take a small amount of soap out of the pot and place it on a saucer for the “ball test” (as described for DBHP).
  6. When the soap is cooked, add the extra ingredients and then proceed as described for DBHP.

From the above description, Oven Hot Process sounds a lot easier than DBHP… but there are some important additional considerations:

  • Mixing temperatures are just as important with OHP as they are with Cold Process soap. Soap mixes that are too hot will volcano out of the pot, with terrible consequences for your oven.
  • The oven temperature must be constantly low, and it’s not always easy to reach the ideal cooking point. This depends, but it’s not limited to, on how long your oven “stays warm” after being turned off.
  • If the ball test at the end of the cook shows that the soap is not ready yet, you can turn the oven back on for a few minutes, and then leave the soap pot in the oven for 10 to 20 minutes. The only way to work out the ideal cooking times for your soap batches and recipes is to experiment and take notes.
  • When the soap is cooked, essential or fragrance oils and other additives can usually be added straight away (remember, the soap has been sitting in a turned off oven for an hour, so the temperature should already be below 60ºC – 140ºF). In general, OHP soap is more fluid and easier to mould than DBHP.

Marina‘s versions of double boiler and oven hot process soapmaking methods (DBHP, OHP):
Pro and cons of cold process vs. hot process soap

Deciding whether Cold Process is better than Hot Process, or vice versa, is just a matter of personal preference and soapmaking “culture” – a bit like deciding whether holidaying at the beach is better than mountain trekking, or whether black tea is better than white tea!Both methods offer specifically advantages and disadvantages, and in our experience, the best way to choose is for you to read through the instructions and warnings for both basic soapmaking methods (Cold Process, or CP, and Hot Process, or HP), evaluate pros and cons, make up your mind based on your expectations and skills, and then apply the “golden rule”: try for yourself, and see if you’re happy with the results!The advantages of Hot Process soap are, by general agreement, basically three:

  1. Soap is completely saponified quicker than in Cold Process soap.
  2. Essential and fragrance oils, superfatting oils, and other additives are added at the end of the cook and are not affected by the saponification reaction.
  3. Hot Process soaps are easier to slice and do not crumble. For this reason, they offer a better alternative for those soapmakers who prefer to cut their soaps “on request”.

There are however a few disadvantages, including the following:

  • At the end of the cook, the soap paste is less fluid than with Cold Process, and not as easy to work with for moulds designed for larger batches (such as divider soap moulds, for instance).
  • Soapmakers disagree on the effects that cooking might have on the base oils, and some argue that cooking will reduce or destroy altogether the “live” properties of the oils. If it’s true that even Cold Process soap must undergo an exothermic reaction, the difference between the highest temperatures reached by Hot Process and Cold Process is approximately 30ºC, which appears to justify these concerns.
  • Although it’s true that Hot Process soap can be used as early as a few hours after the end of the cook (and this is because the saponification process has been completed during this phase), no handmade soap can be considered truly ready to use in less than 4 weeks. As a matter of fact, because it uses a larger amount of water than Cold Process, Hot Process soap tends to require longer curing (drying) times than Cold Process soap.
  • Cooking represents an energy waste, which can be avoided with Cold Process soap

Marina‘s versions of double boiler and oven hot process soapmaking methods (DBHP, OHP) – Overview

Please notice these suggestions are made available as general information only. Soap making from scratch implies working with dangerous substances, such as caustic soda in its pure form (NaOH – sodium hydroxide, or KOH – potassium hydroxide). We do not assume or accept any responsibility for, and will not be liable for the accuracy or inappropriate application of any information whatsoever in any material on this website.
If you prefer to avoid working with strong lye solutions, you can choose the easy road and purchase a natural soap base for hand milling, also known as rebatching or, less appropriately, as remilling.


In the last few years, several Hot Process soapmaking methods have been devised, defined and made available. I have chosen to describe here the two I know best: the Double Boiler Hot Process soap making method, and the Oven Hot Process method. Although I have not “invented” either of these soapmaking methods, I feel I have acquired sufficient experience, over several years, to describe them in detail, and offer my personal versions of both.It is however important to note that soapmaking is not suitable for everyone and all. Safety considerations are paramount when working with “lye”, and we assume the reader is 100% aware of the risks, and can take total responsibility for the consequences.Before attempting to make soap for the first time, you might like to check out some basic safety considerations for a run down of the precautions required when working with strong alkalis. For further and general background information about soap and soapmaking, please refer to my soap methods overview and my versions of traditional cold process soap and discounted water cold process methods.

What is Hot Process soap making?

In short, HP (hot process) soapmaking methods are ways to make soap that, by applying extra heat after trace, is fully saponified within a few hours. As explained in my cold process soapmaking method, soap is the product of a chemical reaction (called “saponification”) where fatty acids, combined with an alkali, give a salt (=soap) as the final product.When extra heat (that is, some sort of “cooking”) is applied to the soap mix, saponification occurs within 30 to 90 minutes, depending on batch size and ingredients. Hot process soap is therefore ready to use, at least from a strictly chemical point of view, very quickly.I would however like to point out that, in my experience and professional opinion, even soap that is fully saponified at the end of the process (such as Hot Process soap, for instance) must be cured (that is, allowed to lose excess water, as well as possibly residual free alkalis) for at least 4 weeks. Although longer curing times are particularly important for cold process soaps, it’s a fact that good soap always needs correct curing times. As I like to point out to all those who ask my advice… if soapmaking could be described in one word, that word would be patience – and patiently waiting for Hot Process soap to undergo a reasonably long curing period is only going to give you better and more satisfactory results.Source: Aqua Sapone


5 Responses to "Double Boiler Hot Process Soap Making Method (DBHP) and Oven Hot Process Soap Making Method (OHP)"

Hot Process requires a water ratio of 0.35-0.375 parts of water for each part of oils.

tahun 2002 saya gunakan formula jumlah air sepertga dari total jumlah minyak, ternyata sabun transparan menjadi lembek. rumusan diatas benar jika hanya menggunakan stearic acid dan minyak kelapa saja.

gimana menurut bapak?

Not that I’m impressed a lot, but this is more than I expected for when I stumpled upon a link on Digg telling that the info here is quite decent. Thanks.

Thanks for this information. I have done hot process several times using a crock pot with good results. I plan to try a double-boiler in the future, as this will free me from the size limitation of the typical crock pot. I also plan to buy an outdoor burner (like Bayou Classic) and a large stainless steel double boiler. That way, I can do larger batches and do all the work outside.

One thing I do not understand is why the article above says “despite being usable only hours after making hot process soap, no soap is truly ready to use in less than 4 weeks”… I am not sure why? My hot process soap is at a usable pH and hardness within a day. Like any soap, if I leave it to sit for a week or two, it will continue to get harder and drier…but I consider it “truly ready to use” within days if not hours. If it is properly saponified, I know of no other reason why it would not be.

First off I want to say excellent blog! I had a quick question in
which I’d like to ask if you do not mind. I was interested to find out how you center yourself and clear your thoughts prior to writing. I’ve had difficulty clearing my thoughts in getting
my ideas out. I truly do enjoy writing but it just seems like
the first 10 to 15 minutes tend to be lost just trying to figure out how to begin.
Any suggestions or tips? Kudos!

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