Hair porosity in relation to effectiveness of dye

Right, so when the hair is more 'porous' it means that the cuticle has been roughed up and bits are sticking out from the hair shaft, so that means that more dye can get under them, which is what makes bleached hair take semi dye better than unbleached hair where the dye molecules slip off more easily.

The issue with severely damaged hair is that the cuticle is so chipped and lifted that dye molecules can get under it easily, but can also slip out easily. This means that when you wash your hair the cuticle doesn't hold as many of the dye molecules underneath it so your hair fades.

However, staining still seems to be an issue with over bleached hair, maybe because dye molecules are wedged in to the cortex? Or just deep enough under the cuticle that it won't wash out. I'm not sure on that one.

The less pourous hair being more difficult to shift staining thing does kind of make sense if you don't think about what causes porosity. But the ting is that porosity is caused by damage to the cuticle. Anything which pushes dye molecules under the cuticle, which is how to cause staining, will have to lift the cuticle, therefore making the hair more porous. Getting staining on virgin, undamaged hair is pretty damn difficult.

Basically what I'm trying to say is that none of it is really contradictive if you think about what actually causes porosity and therefore defines how well dye will stick.

Sorry that was so long 😛

Thank you very much

Okay, so on normal bleached hair, dye sticks better because it's more porous
But on severely damaged bleached hair, it sticks but washes out really easily because it's very porous

That makes sense

& I get that staining on very porous hair may make sense if it does get into the cortex. Or as you say maybe the deeper layers of the cuticle.

But I'm still a little confused about less porous hair.
My hair cuticles lie pretty flat on my hair. When I had virgin hair I dyed it red with MP and it took ages to shift the colour. Another time I did it, I left it on for 6 hours and hair dried it in! That's when I got really bad staining and the only thing that got it out was a colour remover.
I don't understand why it did this, my hair was in very good condition. I understand maybe heat pushed it in, but the first time it still took a while to fade completely even when I didn't use heat.
I've also heard a few times that Virgin hair is prone to staining.

Heat does cause the cuticle to lift, so it is possible that the heat used lifted the cuticle, allowing the dye molecules under, then when trapped the dye molecules in when it was cooled and laying flat.

I have not heard much about Virgin hair staining, in my experience Virgin hair doesn't hold on to dye long. So I'm not sure about that.

Yeah I agree, it must have been the heat.
I'm just still confused about the long-lasting red on my unheated Virgin hair since theoretically I would assume it should have completely washed out very quickly. I didn't do anything to raise the hair cuticle, the the dye should have just stuck the the outside.

I highly doubt it was due hair porosity. When I run my fingers over my Virgin hair stand backwards, it feels the same as it does when I do it foward so surely my hair cuticle is not very raised. And it wouldn't be raised anyway because my I never bleached my hair (at the time I dyed it red) and only blow-dried my hair (and never to access).

Hmm who knows what it was then

As for why I was confused I think it's because I was trying to come up with a rule of how long hair dye lasts in relation to hair porosity. & I only took into account high porosity and low porosity, whereas I didn't think of any in between stages.

& I think the reason I thought there was a contradiction was because very porous hair takes dye quickly, but it gets washed out quickly, so I didn't understand the staining, but now I have an idea of how that could be possible.

& probably my experience of staining on Virgin hair which went against what's supposed to happen

But I get it now thank you

So: high porosity - hair dye penetrates more due to lifted cuticle, but washes out dye to lifted cuticle. & possibly can still stain if the dye penetrated into the deeper layers of the cuticle or into the outside of the cortex.

Medium porosity - hair dye doesn't penetrate as much, but doesn't wash out quickly because hair cuticle is only slightly raised. Which explains why it's best to have bleached hair that isn't too damaged because the hair dye sticks well and lasts pretty well

Low porosity - the hair dye should wash out very quickly without staining because the cuticle lies pretty flat so the dye mostly sits on the outside of the hair strand. Perhaps it's only possible for it to last a long time if the hair cuticle gets raised and the dye gets inside and it gets sealed afterwards

I'm pretty sure that's right then

Yeah that looks right!

I'm really unsure as to why you got staining on Virgin hair. Sorry I can't be more useful there.

@Marthakins thank you very much! I'm happy that all makes sense now
As for the staining of Virgin hair I guess I don't need to worry about it anymore since I bleach my hair now anyway.

You're welcome 😀

Some dyes stain more than others, regardless of how open/closed or complete the cuticle is. Was the red you used Vampire red? It is notorious for staining even on virgin hair.
If you had used a different dye you would have had trouble getting it to stay. Sticky dyes stain the cuticle regardless of whether the dye penetrates.
There is no rule regarding porosity and longevity of hair dye Im afraid. If you look at long hair with faded colour the tips usually wash out first, the mid lengths are faded and there is usually a band of bright colour left near the roots. That shows how porosity affects how colours hold. Very damaged hair with parts of the cuticle missing will struggle to hold any colour at all.

I agree, some dyes are just very heavily pigmented and stain anything!

I used MP rock n' roll red, which stayed for quite a whole, like a had a red tinge for months. Then when I did the l the hair drying in that was with MP wildfire and MP infrared. I actually tried to dye my hair with adore paprika and adore Cajun spice but that washed out in only a few washes. I guess because MP is quite thick and gel-like and adore is very thin and watery, like you mentioned.

Thank you very much for all your responses, they've been really helpful.