There’s cold process, hot process, and melt and pour soap making. Add another method of DIY soaping to your arsenal: room temperature soap making (sometimes called the heat transfer method). These two terms are often used interchangeably.
At its most basic, room temperature soaping involves allowing lye and oils to cool to roughly room temperature. Some people prefer to soap at cooler temperatures to prevent additives like milk or honey from scorching.
The heat transfer method is a variation of the cold process method with a twist: it relies on the heat from the lye mixture to melt hard oils instead of using a traditional heat source (such as a stovetop).
Read on to learn more about how temperature affects your finished soap, along with a step-by-step guide to using the heat transfer method.
What is room temperature?
Seeing as this article is about room temperature soap making, I thought it best if we define what room temperature actually is. It turns out there’s no clear-and-cut answer. However, most people agree that room temperature is roughly 68 degrees Fahrenheit (20 degrees Celsius), give or take a few degrees.¹
In reality, the actual temperature of various rooms within the same house may vary according to a variety of factors. Outdoor temperature and thermostat settings all play a role in the actual temperature of a room, fluctuating by time of day and season.
(Compare a kitchen in Canada during an ice storm vs. a home in Florida during summer, for instance.)
It’s important to keep your ambient room temperature in mind when making your next batch of homemade soap. The room temperature affects whether your soap goes through gel phase, and how fast or slowly liquids cool.
And when you use the room temperature soap making method, there’s no hard-and-fast rule to the exact temperature of your lye or oils… which brings us to the next section.
Room temperature soap making breaks the rules
They say rules are meant to be broken, and the heat transfer or room temperature method does just that. You’ve been conditioned since your first batch to follow a few basic soap making rules:
Keep a careful eye on temperatures of oils and lye: With this method, there’s really no need to do this. What temperature do you normally make soap at? Around 110 degrees Fahrenheit (43 degrees Celsius) is a good temperature to combine the lye and oils. The temperature varies depending on the recipe and types of special ingredients you may use, along with personal preferences.
Combine oils and lye when within 10 degrees of each other: Again, this rule doesn’t apply.
Carefully melt hard oils on the stovetop: You can save yourself this extra step!
Tip: The heat transfer method is a variation of the cold process method. It’s recommended you make a few batches of cold process soap first to get the hang of things before trying this method.
Can you use room temperature lye?
Yes, many soap makers allow their lye solutions to cool completely before using. In fact, some soapers prefer to make the lye water solution the night before they actually plan to soap. (If this is you, just make sure it’s placed in a safe spot and clearly labelled!)
There are some potential issues when working with cooler lye. The main issue is the potential for oils/fats and butters to turn hard and solid when cool lye comes in contact.
Not everyone likes to work with room temperature lye. With the heat transfer method, you actually add the lye mixture to the oils when it is freshly mixed and still hot. (We’ll cover the steps to this process below.)
Why you sometimes want to soap at lower temperatures
There’s a range of temperatures that are acceptable within soap making, and everyone has their own preferences. The longer you’ve been making soap, the more knowledgeable you become about how various oils, butters, and other additives come together. You can tweak and adjust temperatures as you see fit.
The temperature of your oils and lye have a huge impact on your finished product. There are a few instances when you may choose to work at lower temperatures:
Working with heat-sensitive ingredients such as milkand other liquids like juice, wine, tea, or beer. Milk especially is prone to scorching when liquids are too warm.
You want to make soap with a matte finish and muted colors. Vibrant colors in your soaps may not be your cup of tea. If this is the case, working at lower temperatures may prevent your soap from reaching gel phase which produces brighter colors.
Your room temperature is on the warm side. If you are making soap in the middle of summer, you may choose to work at lower temperatures.
Working with additives like honey. The sugars in honey make your soap batter get hot super fast! For this reason, you might not want to insulate your molds, and also work with a cooler temperature. Certain fragrance oils may also bump up the temperature.²
You want some extra time to create designs. You’ll get a bit more leeway before you reach trace when soaping at cooler temperatures. This gives you some time if you want to try more advanced techniques like swirling.
Benefits of room temperature soaping (or heat transfer method)
Once you’ve made a few cold process soap recipes, give the heat transfer method a try for straightforward recipes with basic ingredients.
Saves time: Instead of having to wait for your lye mixture and oils to cool, there’s very little downtime with this method. (This is perfect for impatient soapers out there, like me!)
Convenient: If you happen to masterbatch your oils, or your lye, you’ll love this method. You just measure and combine the ingredients and pour into molds!
No need to use your stove: Sometimes room is tight in the kitchen, especially on the stovetop. With this method, you don’t require the use of an external heat source—you’ll use the heat from your lye mixture.
Heat transfer method: step-by-step
The heat transfer method is just a variation of cold process soaping.³ If you’re new to the world of soap making, please read up on soap basics and lye safety first!
Gather your soap making supplies:
Digital kitchen scale
Thermometer (digital, infrared, or candy thermometer)
Immersion blender (stick blender)
A large heat-safe and non-reactive bowl for mixing the hard oils
A large bowl for the liquid oils
Heat-safe jug for the lye solution
Rubber spatula or small non-reactive whisk for stirring and scraping the hard oils and lye mixture
Soap mold
Safety gear (goggles and gloves)
Prepare your soap mold and gather all necessary ingredients. If you’re planning to use any colorants, essential oils/fragrance oils, or botanicals, measure these out beforehand.
Measure out hard oils. Measure all hard oils and place into a large heat-safe bowl. This includes lard, tallow, coconut oil, shea butter, etc.
Measure liquid/soft oils. Measure all liquid oils into a separate bowl.
Make your lye solution. Using your heat-safe jug, weigh water, followed by sodium hydroxide lye. Add the lye flakes to the water (never the other way around!). Your lye solution becomes very hot! Mix carefully with a spatula or whisk. Allow the lye mixture to become clear before adding to the hard oils.
Pour the lye solution over hard oils and mix until melted. Once the lye mixture has become clear (no longer cloudy), it’s time to let the hot lye mixture do its magic. Carefully pour the lye mixture over the hard oils which are solid at room temperature. You’ll see the oils slowly melt while a few chunks remain. Use your spatula or whisk to carefully mix the hard oils until completely melted.
Add liquid oils. Pour your liquid oils and combine with the melted hard oils. Use your immersion blender to reach trace. (It’s a good idea to alternate between manually mixing with a spatula or whisk, and using the stick blender.)
Add colorants, fragrances, and other additives. Customize your soap batch by adding in the pre-measured additives. Blend in.
Pour into soap molds. Once soap has hardened, unmold and cut your bars as usual. Allow to cure for 4–6 weeks.
Possible pitfalls of room temperature soaping (or heat transfer method)
It’s not all sunshine and rainbows in soap making (if you’ve ever had a failed batch of soap, you know what I mean). But this is all part of the fun and the learning process. This method of making a batch of soap from scratch isn’t foolproof. Instead, think of it as another method of making soap you can add to your toolkit and break out as needed.
Soda ash: Sometimes your finished soap develops a layer of white, powdery stuff—this is soda ash. It occurs when soaping at cooler temperatures and develops as a result of unsaponified lye reacting to carbon dioxide in the air.
False trace: Sometimes when oils cool down too much, they turn solid and reach what soap makers call “false trace.” It appears like the soap batter has thickened and saponified, when it reality, it hasn’t. Use your immersion blender to remix as needed.
Tips for success when using the heat transfer method
Consider the recipe and the ratio of hard or brittle oils vs. soft oils. For example, palm kernel flakes are an especially brittle oil that may take a bit of elbow grease and patience to melt.
Beware of recipes with beeswax. As beeswax has a higher melting point, you may need to use the traditional cold process method to fully melt this ingredient.
Ensure hard oils have completely melted and are clear before adding liquid oils.
Josh is co-founder of RusticWise. When he’s not tinkering in the garden, or fixing something around the house, you can find him working on a vast array of random side projects.
The Heat Transfer Method for making Cold Process soap uses the heat from the Sodium Hydroxide (lye) when mixed with water to melt hard oils and butters. This can save time in the soap making process, but is considered a more advanced process of soap making.
The temperatures in both the soapmaking ingredients and the room temperature in which you are making soap can affect how quickly a soap traces. The higher the temperatures, the faster the trace times. Ideally, your temperatures should be below 110 degrees F for best results.
In general, there are four methods to make soap - cold process, melt and pour, hot process, and rebatch. There are pros and cons for each, and every maker has a personal preference.
It may be defined in science, but in practice it's 20 to 22 degrees Celsius or 68 to 72 degrees Fahrenheit. Room temperature is defined as the thermometer reading of a room. Ideally, it is the temperature at which people feel comfortable wearing ordinary clothing.
room temperature. noun. : a temperature of from 59° to 77°F (15° to 25°C) that is suitable for human occupancy and at which laboratory experiments are usually performed.
Energy.gov suggests that 68 degrees is a good room temperature while you're awake at home but recommends lowering it while you're asleep or away. Lowering your thermostat 7-10 degrees for eight hours a day can reduce your annual heating expenses by as much as 10 percent.
Temperature plays a very important part in soaping. It can affect the trace, color, texture and scent of your final soap. In general, we recommend soaping at around 120-130 ° F. This means that both the lye and oil are this temperature range immediately before the two are combined and the saponification process begins.
by Rhonda Gaylord. Weigh out your soap, depending upon what size mold you are using, and cut your soap base into small cubes. Cutting the soap base into cubes will help melt your soap faster without using a lot of cooking time (heat).
Commonly referred to as MP, melt and pour soap making is probably the easiest way to get started with soapmaking. It's as simple as buying a commercial premade base of soap, melting it down, adding in your goodies (like scent, color, botanicals, and more), and letting it set up.
Saponification is a process that converts fats, oils, or lipids (the acid) into soap by combining them with Sodium Hydroxide (the base). The chemical reaction relies on friction and self-generated heat.
Hence, Radiation is the fastest mode of heat transfer because the heat gets transferred as electromagnetic waves. Radiation transfer energy in a vacuum also.
What are the 4 Types of Heat Treating Processes? Common types of heat treating methods include annealing, hardening, quenching, and stress relieving, each of which has its own unique process to produce different results.
The term "room temperature" refers to a temperature range that is suitable for human habitation. Under this temperature range, a person wearing regular clothing does not feel hot or cold.
Technically speaking, the term "room temperature" indicates the temperature inside a specific building or room, while "ambient temperature" means the temperature of the surrounding area. These terms are used synonomously.
Cold: Any temperature not exceeding 8°C (46 °F). Room temperature: The temperature prevailing in a work area. Controlled room temperature: The temperature maintained thermostatically that encompasses at the usual and customary working environment of 20°-25° (68°-77 °F).
Thermo-hygrometer is a device that gives you a measurement of the temperature and humidity of a place with one device. They prove to be very important in fields where temperature and humidity play an important role such as breweries and fermentation units, pharmaceutical incubators, plant growth chambers, etc.
What Does Room Temperature Mean in Baking? When you are bringing ingredients to room temperature you want them to be around 70 F (21 C). This is the temperature at which butter is soft but is not starting to look greasy or glossy yet.
For example, the ideal temperature of a living room should be around 20 to 22 degrees. This is a room for relaxing in, and where you sit for long periods of time, meaning it should be on the warmer side. Meanwhile, the best temperature for a bathroom or child's bedroom should be warmer too at 22 to 24 degrees.
It works by monitoring the air temperature and turning on the heating when the temperature drops below the thermostat preset. Once the desired temperature is reached, the heating will turn off. Digital thermostats, unlike traditional radiators, have a digital display for temperature and controls.
As mentioned before, the use of heat definitely impacts the rate of the saponification reaction. If the reaction takes place at a temperature higher than 120°, the raw soap will saponify too quickly and become thick.
It can be concluded that the oil yield, saponification value, free fatty acid, acid value, peroxide value and iodine value decreases with increase in heating temperature, while heating temperature has no significant effect on the specific gravity of the oil.
The average waiting time before you can unmold your cold process soap is 17-24 hours. If your soap is 100% olive oil soap (Castile soap) then it will need several days to a week or longer. For salt bar soap, you must check it often and it should stay in your mold for 3-14 hours.
For most soapers, the preferred temperature of soaping lye and oils are 120-130 ° F. In addition, many soapers and books believe it is helpful to have the lye and oil within 10 degrees of each other. The temperature range of 120-130 ° F is popular for several reasons.
Soap forms scum when used with hard water (water that contains a high amount of calcium in solution). The scum stops the surfactant properties, so one tends to use more soap. Soap leaves deposits of carbonate salts on the skin. This irritates the skin.
When soap is microwaved, the air trapped inside of the soap heats up and starts to expand.The water inside the soap also heats up and will turn to steam. As the gases grow in volume, they push on the remaining soap ingredients, expanding the bar from something small and compact to a fluffy blob.
Melt and pour soap can be melted in the microwave or in a double boiler. If using the microwave, be sure to use short bursts of heat. Remember, you can also microwave the soap for longer…but once the soap is burned, there is no going back!
Can I melt my MP Soap Base on a stove top? The best way to melt your melt and pour soap is with a double boiler. Melting soap on direct heat will likely cause the soap to burn. If you do not have a double boiler, you can use a microwave and a microwave safe glass container.
The benefits of natural soap making ingredients like coconut oil, shea butter and olive oil can lessen through the heating process in hot process soap techniques; however, the cold process method ensures these natural ingredients are better preserved.
Cold process soap making is the original, traditional method of making soap by combining fat or oil (animal or plant based) with sodium hydroxide lye then blending in addition of essential oils and colorants as required. This treatment causes a chemical reaction called saponification which takes up to 48 hours.
Hot process uses an external heat source to bring the soap to gel phase, where it is then poured into the mold. This is contrary to cold process, which does not use external heat; the heat is internally generated during saponification and the soap may or may not go into gel phase.
Saponification is the name of the chemical reaction that produces soap. In the process, animal or vegetable fat is converted into soap (a fatty acid) and alcohol. The reaction requires a solution of an alkali (e.g., sodium hydroxide or potassium hydroxide) in water and also heat.
Soap likely originated as a by-product of a long-ago cookout: meat, roasting over a fire; globs of fat, dripping into ashes. The result was a chemical reaction that created a slippery substance that turned out to be great at lifting dirt off skin and allowing it to be washed away.
In an oven, the hot air flows by natural or forced convection while heat is distributed from the heating element by radiation. During baking process, heat is also transfer by conduction from the baking metal container to the baked product.
This process of making soap is known as saponification. The common procedure involves heating animal fat or vegetable oil in lye (sodium hydroxide), therefore hydrolyzing it into carboxylate salts (from the combination of carboxylic acid chains with the cations of the hydroxide compound) and glycerol.
There are several other soaping techniques that fall somewhere in between, like CPOP (cold process oven process), HPOP (hot process oven process), but melt and pour, cold process, hot process and rebatch are the “main four.” Each of them creates a great bar of soap, but in very different ways.
The most efficient method of heat transfer is conduction. This mode of heat transfer occurs when there is a temperature gradient across a body. In this case, the energy is transferred from a high temperature region to low temperature region due to random molecular motion (diffusion).
1: Conduction: Heat transfers into your hands as you hold a hot cup of coffee. Convection: Heat transfers as the barista “steams” cold milk to make hot cocoa. Radiation: Reheating a cold cup of coffee in a microwave oven.
Introduction: My name is Mrs. Angelic Larkin, I am a cute, charming, funny, determined, inexpensive, joyous, cheerful person who loves writing and wants to share my knowledge and understanding with you.
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