• Why are some cosmetic ingredients added hot and others added cold

    Formulating cosmetics can be a lot like cooking.  And just like when you are making lunch or dinner, some dishes and cosmetic formulas must be heated and others can be mixed at room temperature.  Here are some reasons there is a difference.

    Room Temperature Formulating

    Ideally, you would be able to formulate all your products at room temperature (RT). There are a number of benefits such as

    • Faster to make
    • Requires less energy input
    • Easier to make adjustments
    • Less chance of ingredient breakdown

    Of course, there are some downsides like increasing the chance of contamination or getting inadequate blending, but lower temperature formulating is usually the ideal.

    Unfortunately, there are a number of ingredients that you can’t add at lower temperatures plus there are formulations that just won’t form at a lower temperature.

    Why heat cosmetic formulas

    Cosmetic formulations are heated for a few reasons:

    1. Speeds up formulation: While formulating at RT can be quicker, this is not always the case. Some ingredients will more quickly dissolve in your solvent if they are heated up. For example, mixing salt crystals in cold water takes a lot longer for them to dissolve than in hot water.

    2. Some ingredients need it: There are a number of ingredients used in cosmetic formulating that have a melting point that is higher than room temperature. In general, you want to mix things together that are in a liquid state. If you’re using an ingredient like Cetyl Alcohol or Glyceryl Stearate, you’ll have to heat your formula to above the melting point of these materials if you want to incorporate them into the formula. It doesn’t matter how long you mix Cetyl alcohol in water, at RT it won’t dissolve.

    3. Make some formulas possible:  While it’s possible to mix the oil phase and water phase at RT, it’s not likely that you’ll be able to produce a stable emulsion using standard emulsifiers. In fact, some mixes of oil and water will not form any emulsion at a lower temperature. Heating your different phases, then blending them at a higher temperature helps make smaller particles that will then be more stable.

    4.  Makes it easier to fill: Typically, lower temperature batches tend to be thicker. This can be a challenge when you are trying to fill the formula into a bottle or finished product container. For this reason formulas are heated up to around 35C. This keeps the formula fluid and makes it much easier for filling. As it cools down in the package it will thicken up.

    Ingredients added as you cool down formula

    While there are a number of benefits to hot batching, there are some ingredients that you shouldn’t add hot to your batches.  This is because they can chemically change when heated. Ingredients like formaldehyde donor preservatives will convert to formaldehyde too quickly so they lose effectiveness. Some of the components of the fragrance will evaporate off so the product won’t smell right. Some proteins or enzymes will chemically denature if heated too high. Many botanicals will chemically degrade if heated too high.

    So, ingredients like fragrances, heat-sensitive preservatives, and active ingredients are all added at cooler temperatures.

  • Understanding US FDA Regulations for Cosmetic Color Additives

    I always suggest a review of regulations as the first step in selecting color additives for use in making cosmetics. Colorant regulations can limit the use to certain cosmetic applications and percentages and can also vary by the country in which the product is sold. I recently watched a formulator scramble to replace D&C Red 7 Lake in an eye shadow color at the last minute after realizing it’s not permitted for eye area use in the United States.

    US Color Regulations

    There are two important definitions to consider when interpreting the color additive regulations for cosmetics.  These include the terms ‘cosmetic’ and ‘color additive.’  According the US Food and Drug Administration (FDA) the term cosmetic means

    articles intended to be rubbed, poured, sprinkles or sprayed on, introduced into, or otherwise applied to the human body or any part thereof for cleansing, beautifying, promoting attractiveness, or altering the appearance and articles intended for use as a component of any such articles; except that term shall not include soap.

    And the definition of color additive is

    …any material, not exempted under section 201(t) of the Food, Drug, and Cosmetic Act, that is a dye, pigment or other substance made by a process of synthesis or similar artifice, or extracted, isolated, or otherwise derived, with or without intermediate or final change in identity, from a vegetable, animal, mineral or other source and that when added to a food, drug, or cosmetic or to the human body or any part thereof, is capable (alone or through reaction with another substance) of imparting color thereto.

    In the United States, the permanent list of approved colors is divided into two categories.

    Certifiable Color: The list of certifiable colors is comprised of synthetic, organic colorants. A sample of each batch of these additives must be sent to the FDA for analysis. If the batch meets required purity standards the FDA issues a certification number to the manufacturer. The manufacturer of the colorant must display the certification number on the label of the package in which the color additive is shipped and on all associated paperwork. In addition, the cosmetic company that purchases certified color additives must keep a record of where the batch of colorant was used in production.

    Exempt Colors: Batch certification of exempt colors is not required, but purity specifications must adhered to by manufacturers and consumers of these colorants. This category is primarily comprised of inorganic pigments, but there are exceptions like carmine, which is the aluminum or calcium-aluminum lake on an aluminum hydroxide substrate of carminic acid.

    The FDA’s website is a great resource for information on color regulations. The following will be useful:

    Table of permitted color additives
    Basic requirements for cosmetic color additives

    If you have any questions, feel free to leave a comment below.