Certain hair types are naturally more porous than others, also one can do a heck of a lot of damage mechanically, not simply heat or chemicals. My understanding is that part of porosity is the presence or absence of the protective fatty layer on the hair, this can be destroyed by a single hair dye session, UV damage, brushing/ combing, any shampoo soap or alkaline product like baking soda. Sulphates are certainly major culprits but not the only ones, all shampoos are designed to break down lipids.

The canopy can suffer from incidental sun damage, the UV protectants in hair products are low factor and chemical not physical so they need reapplying regularly. Naturally porous or damaged hair will suffer hygral fatigue simply from washing and, according to Komaza Care, also during long deep conditioner sessions. Solutions include wearing a hat every time you are near the sun and consider using coconut oil to reduce porosity and protect from protein loss.
Originally Posted by Firefox7275
Very interesting!

You're saying the sulfates in shampoos make hair more porous. It this permanent to those strands or can that actually be repaired?

It's also interesting about long deep conditioner sessions. Can you point me to those articles?

When you talk about using coconut oil to reduce porosity and protect from protein loss, do you mean using it as a sealer after all other products are applied? Or do you mean using it in general to condition the hair?

I don't know if my hair is porous or not, but I'm starting to think it is. Gray hair tends to be porous anyway.
Salt & pepper wavy mix 2B/2C
Low to normal porosity, coarse, kinky, normal elasticity
Current favorites:
Low poo: Yes To Cukes Color Protection (the no sulfate one)
Conditioners: Renpure MPHIP, CJ Smoothing Lotion, AB LI, CJ Curl Rehab, CJ Argan/Olive, Darcy's Pumpkin
Style: FSG, BRHG
Pre-poo/DT: Conditioner with honey & coconut oil

iHerb discount code: PNQ285