Photo of products and hair samples used for this experiment.

There has been a lot of discussion in our Silver Hair groups about heat damage, heat protectants, and how they work (or not).

In this post, I am sharing the details on a little experiment to see how much hair yellows with or without heat protection at different temperatures.

(If you prefer video you can watch on YouTube).


If you follow the Blowout Professor, you may have seen him test heat protectants on bread.

  • While bread and hair aren’t the same thing,
  • Bread ignites at around 480°F
  • And Hair begins to essentially melt at around 450°F

His experiment had me wondering about a few things:

  1. How are heat protectants tested in the lab to get their temperature rating?
  2. What are the different types of heat protection?
  3. When does heat start to yellow gray hair?

Thus began my research and my own experiment.

Disclosure: The product links in this post may be affiliate links. As an Affiliate, I earn from qualifying purchases, at no additional cost to you. Read my Terms and Conditions Page to learn more.

Click any product name I mention or the photo and the link will take you to the product page for purchase.

When does heat damage hair?

Between 248°F and 392°F heat degrades the proteins in your hair, this oxidization turns the white hair yellow. After about 420°F the hair will start to feel rough and can burn the cuticle, essentially the keratin is melting.

The degradation begins sooner than you think: Depending on the source, hair damage begins to occur at 230°F, after 365°F various heat related issues arise, and hair will burn at 450°F.

Loss of water in the hair strand begins between 122°F to 248°F, this is most often the temps on modern hair dryers. If you use a flat iron with wet hair, you increase the damage to the hair via three issues:

  1. Cracking the cuticle because it dries before the cortex does.
  2. When the steam escapes the hair with high heat, it causes bubble fractures.
  3. In addition, the medulla and the cortex are broken down by the steam escaping.

On gray hair this will make your hair weaker, frizzier, and cause a lot of breakage in addition to the dreaded yellowing. The moral is, don’t use irons on wet hair!!!

Key Points:

On dry hair irreversible damage begins at 392°F.

On wet hair irreversible damage begins at 320°F.

Flat and curling irons with their direct contact high heat, are the most damaging heat styling tools when temps aren’t regulated below 365°F.

Hair dryers are often the least damaging since many do not exceed 250°F. However, I still maintain for gray hair that yellowing will get you if you are using your dryer on high and with no heat protection. If you are using a diffuser the damage will be further mitigated.


Thank you to TRI Princeton for your Heat Protection and Testing Information.

I go into full details in my Ultimate Guide to Heat Damage on Gray Hair it is definitely worth the read.

How do heat protectants work?

While the research is still out, it is currently the belief that there are four primary types of heat protection:

  1. Water based heat protection, these dissipate the heat mainly because the water takes on the heat before the hair does; however as mentioned above, this is problematic because wet hair is far more prone to heat damage than dry hair.
  2. Bundles of hair are believed to have a better defense against heat damage, simply becuase the outer hair in the bundle protects the inner hair. Good news curly girls, your curl clumps will likely be protected because those clumps are hair bundles.
  3. Polymers may provide heat protection, research is still out, but it would be similar to water in that the polymer takes the heat on before the hair strand does.
  4. Conditioning agents that coat and protect the hair cuticle will also provide heat protection simply by their ability to add softness, slip, and protection.

And then, of course, there is any combination of the above to improve heat protection results.

How is heat protection tested in the lab?

This was a question I had, and I reached out to one of the scientists at TRI Princeton which is a lab that tests hair products among other things. They sent me over an article that described their processes, plus some of the information I have provided in this blog and the corresponding video.

There are two primary tests for testing heat protection:

  1. Differential Scanning Calorimetry (DSC) – this is a thermal analysis that measures the protein damages in the hair while heat styling, it basically concludes a yes or no answer that the ingredient or product is protecting the hair.
  2. Automated repeated grooming (hair breakage) testing – this test is exactly as it sounds, hair is repeatedly brushed and combed to test for breakage. It can help with heat protection claims because heat usually causes breakage.


I was able to reach out to SEEN and ask how their products were tested for heat protection and they verified that they used both DSC and Automated repeated grooming.

I have landed on a VISUAL and TACTILE test, my goal was to test the hair for any visual changes i.e. yellowing, or changes that could be felt to the touch; as consumers, these are the tools we use to decide if products work or not.

White Hair Samples:

To begin this experiment, I needed white human hair samples. Turns out that was going to be the hardest thing to find for my experiment.

First, I ordered natural hair samples, when they got here, they ended up being animal hair, and were not white but more a cream color.

Then I order three different human hair samples all in white-blond because I couldn’t find anything other than very expensive extensions in real white. I did not want to ruin expensive human hair extensions for this so out of the three sets of samples I chose the lightest.

Sample Hair Type:<br /> Pattern: 1 - Straight<br /> Texture: Normal/Medium<br /> Processing: Possibly Bleached<br /> Porosity: Medium to High 3-4<br />

Prepping the Hair Samples:

  1. Washed samples with Loma Violet Shampoo to tone the yellow down a little
  2. Conditioned each hair sample with Seen Deeper Conditioner
  3. Dried with a diffuser all the hair either with or without the heat protectant depending on the instructions.
  4. Labeled 2 sets of samples with a C for Control, 0 for no product, and 1-8 for each product.
  5. Sample 8 is a product with no heat protectant claim.
  6. First round of flat ironing was at ≈365°F on one set and ≈430°F on the second set, 20 passes each.
  7. Documented the first round of results.
  8. And repeated another 20 passes on each set.

NOTE: As we go through the products and the results you will notice I am telling you about the UV protection claim. I did this for three reasons:

  1. UV protection is necessary for gray hair because UV damage is the number one cause of yellowing on gray hair… WE CANNOT AVOID THE SUN.
  2. Many people believe that heat protectants protect against UV damage, and that is not the case. While the sun is HOT, it is not the heat that damages the hair but the UV rays.
  3. While some heat protective ingredients also protect against UV damage — not all do, they are not all created equal. You want a product that claims both HEAT & UV protection. I will often default to UV protection, in my own product selection, over heat protection (but I don’t flat iron my hair very often).

Disclaimer: This was an informal experiment the results were based on my observation and personal opinion. Depending on use, hair type, and hair tools, results may vary greatly. The photos are not altered for color in any way.

Heat Protectant Experiment

Let’s begin, shall we.

Sample 1: Loma Nourishing Oil:

Heat protection up to 450°F

  • Dimethicone
  • Adansonia Digitata Seed Oil (Baobab Oil)
  • c13-15 alkane (Hemisqualane)

UV protection

  • Trisiloxane

Performed very well, but product does steam with iron. No noticeable change to the feel of the hair. Yellowing began with the 430°F.

Great if you want a silicone-based heat protectant.

2nd Place

Loma Noursihing Oil Heat Protection Experiment side by side of samples

Sample Two: Bumble and Bumble Hairdresser’s Invisible Oil Heat Protectant

Heat protectant up to 450°F

  • Coconut Oil, Argan Oil, Grape Seed Oil, Macadamia Oil, and Safflower Seed Oil
  • Hydrolyzed Vegetable Protein PG-Propyl Silanetriol
  • Hydrolyzed Wheat Protein PG-Propyl Silanetriol
  • Dimethicone

UV protection

  • Butyl Methoxydibenzoylmethane
  • Ethylhexyl Methoxycinnamate
  • Sweet Almond Oil

The samples remained similar in look and feel at 365°F but a slight increase in yellowing at 430°F.


3rd Place

Bumble and Bumble Invisible Hair Dressers Oil Heat Protection Experiment side by side results

Sample 3: Seen Blow-Out Cream

Heat protectant up to 450°F

  • c13-15 alkane (hemisqualane)
  • Squalane Oil

UV protection

  • Moringa Oleifera (Horseradish Tree) Extract

Sample 4: Seen Magic Serum

Heat protectant up to 450°F

  • c13-15 alkane (Hemisqualane)
  • Squalane Oil


Both SEEN products performed well, no visible changes to color or texture at either temperature.

Still my most recommended heat protection.


1st Place

Seen Blow Out Cream Heat Protection Experiment side by side results
Seen Magic Serum Heat Protection Experiment

Sample Five: Pureology Color Fanatic Leave-in Conditioner

Heat protectant up to 450°F

  • Cocos Nucifera Oil/Coconut Oil
  • Amodimethicone
  • Dimethicone
  • Hydrolyzed Vegetable Protein Pg-Propyl Silanetriol

UV protection

The hair visibly began yellowing on the 430°F samples, the hair feels good, but the smell is terrible, and this would be my least recommended product.

6th Place

Pureology Color Fanatic Heat Heat Protection Experiment side by side results

Sample 6: Kenra Thermal Styling Spray 19

Thermal protection up to 428°F

  • I believe the copolymers provide the heat protection

UV protection

  • Benzophenone-3

Hair stiffened up on first pass; it is a setting product though. I think it yellowed the quickest once I began the 430°F passes, which is fair, it is rated to 428°F.


5th Place

Kenra Thermal Spray Heat Protection Experiment side by side results

Sample 7: Mielle Mongongo Oil Thermal & Heat Protectant Spray

Thermal protection

  • Amodimethicone
  • Peg-12 Dimethicone
  • Argan Oil
  • Grape Seed Oil
  • Hydrolyzed Wheat Protein

UV protection

  • Amodimethicone
  • Mongongo Oil
  • Sweet Almond Oil

Hair feels good, became staticky, and no visible yellowing changes. Not recommended at +430° because no temp rating.

4th Place

Mielle Thermal Protection Spray Heat Protection Experiment side by side results

Sample 8: Bounce Curl Moisture Balance Leave-In Conditioner
Does not claim heat protection but based on these other formulas I do believe it will provide heat protection especially for diffusing curly hair, which this product is designed for curls.

Heat protective ingredients:

  • Jojoba oil
  • Murumuru butter
  • Argan oil
  • Shea Butter
  • Avocado Oil

UV protection

  • Shea Butter

At 430°F this hair was the most visibly yellowed…not rated for heat use.

Honorary Mention for Diffusing Curly Hair

Bounce Curl Mousiture Balance Leave-In Heat Protection Experiment side by side results

At what temp does gray hair start yellowing?

Around 430°F and above, all of my samples began to visibly yellow with each of the 40 passes.

The worst yellowing occurred on the sample with no product, followed by Bounce Curl and then Meille.

Samples of the 365 degree side at 20 passes Heat Protection Experiment
430 degree side 20 passes Heat Protection Experiment
Samples 365 40 passes Heat Protection Experiment
Samples of 430 degree side 40 passes Heat Protection Experiment

Do heat protectants protect silver hair from yellowing?

The answer is yes, but it cannot do it alone.

You have to keep those tools below 365°F

And you should be using modern tools that regulate the temperature.

Temperature rated heat protectants are a MUST for using irons.

Final Take Aways on this Experiment:

  1. First: marketing claims of heat protection up to 450°F simply means they don’t test over that heat because that is the heat which hair will ignite or melt.
  2. At ≈365°F no visible or tactile damages occurred on ANY of the samples…leave that iron below 365°F.
  3. Buy modern tools with heat regulation so you KNOW how hot it gets.
  4. Always apply products as instructed, they have been tested using those instructions.
  5. Section your hair and coat evenly, you cannot get the protection if it is only sprayed on the outer layer of your hair.
  6. Don’t use irons on wet hair to prevent that wet damage from occurring.
  7. Understand your hair type, the thicker and coarser your hair the more resilient it will likely be to heat exposure.
  8. Know that the hair around your temples and face gets finer and thinner as we age, and repeatedly heating that hair with flat irons will cause face framing yellowing. It could be heat or the oils form your hands, as you dry the hair out with heat you can cause it to pick up things like makeup, lotions and the natural oils on your hands, and hair products.
  9. Because of the clumps created with most curly styling methods, diffusing on medium or low heat does not require a rated heat protectant.
  10. Once your hair is dry, styled, and set, do not keep going over it with a flat iron. If you do this on next day hair you probably should reapply heat protectant or only use your tool below 250°F.
  11. The less your hair is exposed to direct heat the better, if you must flat iron or use a curling iron or do a blowout, try to achieve a style you can wear for multiple days.

Photo of Joli Campbell


I hope you found this post educational and helpful.

Thank you for reading. Please feel free to share.

As always it is about so much more than the hair.








Next Suggested Post

Heat Damage on Gray Hair Ultimate Guide to Preventing It & Fixing It

*Affiliate Links:

QuickSilverHair is a participant in the Amazon Services LLC Associates Program. Some of the links on this site are affiliate links to I earn money as an Amazon Associate from qualifying purchases.

QuickSilverHair is an affiliate with several brands, I earn a small percentage from any qualifying purchases, at no additional cost to you.

© Copyright disclaimer: All content is written by Joli A. Campbell or Guests, that content belongs to QuickSilverHair or the respected author. All Images in this blog belong to the women in the picture, myself, or were used with purchase or commercial permissions. I have used their images and names with their permission. Please do not copy or redistribute anything from this site without further permission. Thank you. content disclaimer: content is provided for general information purposes and should not be considered medical advice. Product information is not intended to diagnose, treat, cure or prevent any disease. The hair care content is also for educational use, I am not a hair care professional or dermatologist, please be careful with your hair and skin. If you have any hesitations or concerns speak to your doctor or hair care professional for their support before using any information you find on this site. Be well.

For full Affiliate and Copyright Details Please Read My Terms & Conditions Page

Pin It on Pinterest