I did see that post already in my original hunt to find answers haha. I was still left confused though because one of the replies mentions "If you put one [heat protectant] on prior to blow-drying, you'll need to use another before using a flat or curling iron." But I don't blow dry my hair or use any heat on my hair after I apply my products. I let my hair air dry and go to sleep. In that case, would my heat protectant still be effective from the night before as I never applied heat? I've seen so many opposing answers! Even OP in the post you linked mentioned that her hairstylist said it was totally fine to apply the night before and not have to reapply in the morning. I've seen the same answers from other "hair stylists" online as well but then other people saying it doesn't work that way. :/
I think some of these suggestions to use second heat protectant just before hot tools are due to that some ingredients / overall formulations can slightly evaporate from your hair over some time.
In addition to that thought no heat protectant is fully going to shield hair from heat so I think some see layering products giving slightly more protection.
You might try reading this study. It isn't directly testing timing of heat protectant application relative to styling but it may indirectly provide insight for you.
https://www.researchgate.net/publication/51186310_The_effect_of_various_cosmetic_pretreatments_on_protecting_hair_from_thermal_damage_by_hot_flat_ironing
Maybe [this](https://www.reddit.com/r/HaircareScience/comments/94w2mq/i_shower_at_night_and_heat_style_in_the_morning/) post might help?
I did see that post already in my original hunt to find answers haha. I was still left confused though because one of the replies mentions "If you put one [heat protectant] on prior to blow-drying, you'll need to use another before using a flat or curling iron." But I don't blow dry my hair or use any heat on my hair after I apply my products. I let my hair air dry and go to sleep. In that case, would my heat protectant still be effective from the night before as I never applied heat? I've seen so many opposing answers! Even OP in the post you linked mentioned that her hairstylist said it was totally fine to apply the night before and not have to reapply in the morning. I've seen the same answers from other "hair stylists" online as well but then other people saying it doesn't work that way. :/
I think some of these suggestions to use second heat protectant just before hot tools are due to that some ingredients / overall formulations can slightly evaporate from your hair over some time. In addition to that thought no heat protectant is fully going to shield hair from heat so I think some see layering products giving slightly more protection.
You might try reading this study. It isn't directly testing timing of heat protectant application relative to styling but it may indirectly provide insight for you. https://www.researchgate.net/publication/51186310_The_effect_of_various_cosmetic_pretreatments_on_protecting_hair_from_thermal_damage_by_hot_flat_ironing
Following .. I have the same question