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View Full Version : how much damage to jump from low porosity to normal, and normal to high?



emmadilemma
April 7th, 2016, 10:40 PM
Not really asking for any reason other than curiosity! :o how much damage would you say it takes to jump from low porosity to normal porosity, and how much damage would it take to jump from normal to high porosity? I would think it would be something like suddenly chemically dying your hair followed by like a week straight of harsh heat treatment every day. or maybe thats how you skip normal and damage all the way to high porosity. I would think daily damage along with sudden chemical hair color would take hair from low to high in like a week or two. Just a fun question, not really important :)

lapushka
April 8th, 2016, 03:19 AM
I know I hammer on and on about this, but if your hair is "regular" virgin hair, chances are it's more normal porosity than anything else. Low porosity is *really* a big exception, and I think that is what most people forget. It is hair on which dye doesn't take, chemical services go to hell (no bleach, perms or anything works). So I really don't think there's many of us out there that can state they have "low porosity".

/rant over. :lol:

I think if you go ahead and damage your hair with chemicals and it takes, that the proof is in the pudding, and that you've just gone from normal to high porosity should you go on with this.

AJNinami
April 9th, 2016, 06:00 AM
I think it might happen when your curler won't work on half your head.. I found this out the hard way when doing my hair for prom.

meteor
April 9th, 2016, 01:23 PM
Not really asking for any reason other than curiosity! :o how much damage would you say it takes to jump from low porosity to normal porosity, and how much damage would it take to jump from normal to high porosity? I would think it would be something like suddenly chemically dying your hair followed by like a week straight of harsh heat treatment every day. or maybe thats how you skip normal and damage all the way to high porosity. I would think daily damage along with sudden chemical hair color would take hair from low to high in like a week or two. Just a fun question, not really important :)

Great question! :D
I have some problems answering this question directly for one simple reason: I'm not 100% clear about the very definition of porosity, i.e. what kinds of pores/cavities in number and size qualify as those of "high-porosity" hair, and what kinds are still considered "normal" for natural hair structure, and what kinds are considered "low"? What are the specific thresholds? :hmm: Without clear measurement, it stays pretty obscure and kind of relative (depending on what you compare to - e.g. other people's hair, your own roots vs. ends, etc).

I am assuming that, even without any damaging treatments, the same person's ends (if the hair is long) will still be more porous than roots anyway (due to exposure to UV rays, wear & tear, let alone if any chemical or heat treatments were actually used on it). So within that person's subjective experience, the ends will still be more porous (relative to roots), or at least just as porous (if the cuticle managed to stay intact), but probably not less porous (unless the very structure of the hair changed somehow? maybe with health issues/medication? :hmm:)...

Now, about porosity increasing from chemical treatments... It's pretty well-documented. For example, according to "Chemical and Physical Behaviour of Human Hair" by C.R. Robbins:

Bleached hair has a higher concentration of negative [negative charge] sites at and near the fiber surface to attract and bind cations and is more porous than chemically unaltered hair. As one might predict, uptake of polymer [...] onto unaltered hair was an order of magnitude lower than for bleached hair. (from p. 354) This explains why porous hair absorbs more conditioning ingredients.


Here is a very interesting study on porosity and how it increases with bleaching and UV rays:
- True porosity measurement of hair: a new way to study hair damage mechanisms: http://journal.scconline.org/pdf/cc2008/cc059n04/p00303-p00315.pdf, summary: http://www.ncbi.nlm.nih.gov/pubmed/18818850
I posted an overview on it previously, so I'll just re-post it here, if it's OK:


Tensile Strength of Bleached and Sun-Bleached Hair

Study:
- True porosity measurement of hair: a new way to study hair damage mechanisms: http://journal.scconline.org/pdf/cc2008/cc059n04/p00303-p00315.pdf, summary: http://www.ncbi.nlm.nih.gov/pubmed/18818850

Results:

BLEACH DAMAGE:

The oxidation of cystine due to bleach causes the disruption of crosslinks, which results in the reduced wet tensile strength.

The wet hair tensile strength analysis showed a significant decrease in breaking force (about 20%) after the 1st minute of bleaching, then stabilization and then another decrease in breaking force after 10 min. (pp. 305 - 306)

Tensile strength of bleached hair


Bleaching Time (min)
0
1
5
10
15
20


Total Work Force for Breaking Hair (mJ)
1.718
1.306
1.442
1.118
1.188
1.054

(based on p. 306, see statistical analysis on p. 306 for details)

"The oxidative attack on hair not only causes the breakage of disulfide bonds in hair protein, but it also breaks down the melanins. Wolfram and co-workers (16,17) have investigated the oxidation of human hair with and without pigment. Their research concluded that hair with pigment consumes hydrogen peroxide at a measurably faster rate than hair without pigment, suggesting a faster reaction of peroxide with hair pigment than with hair protein. Based on that conclusion, the initial response of oxidative damage to hair fiber should be color change." (p. 306)
^I wonder, maybe that's why coconut oil is a good oil pre-bleach (due to its affinity to hair's protein, it can protect the hair's protein a bit, while still allowing color to lighten? :hmm:

"The virgin hair has a set of pores that essentially triple (2.83 times) after 1 min of bleaching. The number of pores increases lightly after 5 min of bleaching. The next significant change happens after 10 min, in which the surface area decreases to almost that of the virgin hair. This might be due to the smaller pores breaking down into larger pores. The 15 min of bleaching time is just more of the smaller pores breaking down to form larger pores, while the 20 rain of bleaching time gives a slightly higher surface area, possibly indicating penetration of the walls between the newly created larger pores." (p. 309)

UV DAMAGE:

"UV light degrades the amino acids of the hair fiber at the outer layer (cuticle) to a greater extent than the inter layer (cortex)." (p. 309)

Tensile Strength:
[This study] indicates that the tensile strength already shows a noticeable decrease after 200hr of UV exposure, and it remains unchanged after 400 hours. Finally, there is another significant decrease after 1200 hr of exposure. The results illustrate that UV irradiation already attacks the hair cortex in a relatively short period of time, resulting in decreased tensile strength. However, much longer UV exposure times are needed to further damage the cortex after the initial damage occurs." (p. 310)


Tensile strength of UV-damaged hair


Exposure Time (Hr)
0
200
400
1200


Total Work Force for Breaking Hair (mJ)
1.718
1.143
1.049
0.681

(based on p. 310)

The study shows an immediate loss in surface area in the first 200 hr of exposure to UV rays and a gradual increase as exposure time continues, which is most likely due to the fusion of cuticle cells followed by an increase in pores or cracks.

"We have also found that the different parts of hair show different porosity: hair toward the root has much less porosity than the tip ends, which indicates that hair is more damaged in the tips due to abrasive combing." (p. 314)

The study has some great information on color changing with damaging treatments as porosity increases, as well, so that's another symptom of high porosity. Also, there are some excellent graphs in the study, with details on specific cavity increases. I really recommend checking out the study for figuring out porosity. ;)

As for management, I think conditioning (esp. with temporarily patch-repairing hydrolyzed proteins, 18-MEA, ceramides - http://www.thenaturalhavenbloom.com/2010/08/ceramides-patching-up-damaged-hair.html) and oiling are a good way of managing high porosity.

The presence of exogenous lipids in these cavities was found to be critical in maintaining the mechanical integrity of the cuticle cells. Regions presenting microcavities and cracks produced by reversible deformations were seen to fully recover and heal with the onset of a plasticization effect produced by the synergy of lipids and water. In contrast, microcavities produced by irreversible deformations were always filled with lipids. In both cases the lipids acted as weak adhesives, in particular, in those cavities and gaps opened in the cuticle cell interfaces.
(The effects of lipid penetration and removal from subsurface microcavities and cracks at the human cuticle sheath: http://www.ncbi.nlm.nih.gov/pubmed/19450411)

Here are really good articles, listing things that help manage specifically high porosity:
- http://science-yhairblog.blogspot.ca/2014/03/managing-elasticity-and-porosity-in-hair.html
- http://www.thenaturalhavenbloom.com/2012/10/deep-conditioning-what-ingredients-in.html

meteor
April 9th, 2016, 01:25 PM
I know I hammer on and on about this, but if your hair is "regular" virgin hair, chances are it's more normal porosity than anything else. Low porosity is *really* a big exception, and I think that is what most people forget. It is hair on which dye doesn't take, chemical services go to hell (no bleach, perms or anything works). So I really don't think there's many of us out there that can state they have "low porosity".

/rant over. :lol:

Very interesting. :) I've seen this mentioned on the boards before, too, but I haven't found the original source for this information, unfortunately... :hmm: Does anybody have any links for this? If so, please do share. :flower:
It's just that, in the articles I've seen, they refer to virgin hair at the roots as "low porosity" and then, older, mid-length hair with normal wear & tear from minimal, normal grooming as "normal porosity" and then damaged hair is "high porosity". For example, here is a very good overview by Science-y Hair Blog that is very consistent with the studies I've seen: http://science-yhairblog.blogspot.ca/2012/06/hair-porosity-how-to-measure-sort-of.html. I'm not saying that that's the only way of looking at it (porosity is probably on a spectrum, just like elasticity, thickness, etc), I just haven't seen anything other than that approach in research yet :hmm:, so I would love to read some links to studies that maybe point to a different view on this. :flower:

Also, I think it's important to remember that all hair is somewhat different (it's bound to be, since it's organic matter, after all :) ), and we know from research that there are differences in things like number of cuticle layers, wider/narrower cuticle cells, and cuticular inclination being steeper on some hairs or cuticular interval narrower or wider, etc (e.g. Morphology and properties of Asian and Caucasian hair - http://www.ncbi.nlm.nih.gov/pubmed/16957811, http://journal.scconline.org/pdf/cc2006/cc057n04/p00327-p00338.pdf) and that may result in different number/types of cavities, but I don't know if it's enough to qualify some hair as intrinsically "low porosity" or "normal porosity" or "high porosity"? :hmm: I guess I'm not so sure simply because there isn't a measurement-based definition (specific thresholds for pore size, pore volume and surface area) that I know of to work with...


I think it might happen when your curler won't work on half your head.. I found this out the hard way when doing my hair for prom.

I agree. It would be a pretty late stage of damage and very high porosity (early stages are probably "asymptomatic" unless you use a SEM microscope to look at hair ;) ), but yes, I believe it would be a strong sign that the hair has lost its natural elasticity and doesn't hold styles the same way, doesn't dry the same way, absorbs too much product, absorbs and loses water/oils/dyes fast, etc etc...
Apparently, "Damaged hair can absorb 45% of its weight in water; undamaged hair in good condition can absorb 30%" (L'Oreal Hair Science (http://www.hair-science.com/_int/_en/topic/topic_sousrub.aspx?tc=ROOT-HAIR-SCIENCE^PORTRAIT-OF-AN-UNKNOWN-ELEMENT^WHAT-WE-DO-SEE&cur=WHAT-WE-DO-SEE)), so I guess, water absorption can be an indicator, even though hair is pretty individual, so the numbers may not mean the exact same thing for different types of hair, I'm not too sure...


So, to recap, I would think these changes indicate significant increase in porosity (assuming the very precise gas sorption method is out of reach ;) :
- reduction in tensile strength,
- increased absorption of water and different types of products,
- color changes, and possibly elasticity changes, changes in how hair holds styles, etc...

lapushka
April 9th, 2016, 03:31 PM
Very interesting. :) I've seen this mentioned on the boards before, too, but I haven't found the original source for this information, unfortunately... :hmm: Does anybody have any links for this? If so, please do share. :flower:
It's just that, in the articles I've seen, they refer to virgin hair at the roots as "low porosity" and then, older, mid-length hair with normal wear & tear from minimal, normal grooming as "normal porosity" and then damaged hair is "high porosity". For example, here is a very good overview by Science-y Hair Blog that is very consistent with the studies I've seen: http://science-yhairblog.blogspot.ca/2012/06/hair-porosity-how-to-measure-sort-of.html. I'm not saying that that's the only way of looking at it (porosity is probably on a spectrum, just like elasticity, thickness, etc), I just haven't seen anything other than that approach in research yet :hmm:, so I would love to read some links to studies that maybe point to a different view on this. :flower:

Here's a link where "low porosity" hair is considered "resistant hair":
https://books.google.be/books?id=4GMbPmmWPTsC&pg=PA211&lpg=PA211&dq=low+porosity+hair+chemical+services&source=bl&ots=grFZLGiLnw&sig=BJFTFuaixMDWu07a9go_fLqf9cU&hl=nl&sa=X&ved=0ahUKEwjd9eSUwILMAhWBbw8KHQX9BVAQ6AEIGzAA#v=on epage&q=low%20porosity%20hair%20chemical%20services&f=false

meteor
April 9th, 2016, 04:20 PM
^ Thanks a lot, lapushka! :flowers: Thanks so much for sharing! :D

Interesting stuff! :) Since this is probably of interest to other LHC-ers who are wondering about porosity, I'm going to quote it here (from 2008 ed., p. 430):

"Resistant hair has a tight, compact cuticle layer... chemical services require a (more alkaline) texturizer than porous hair. ...
Hair with normal porosity is neither resistant nor overly porous....
Overly porous hair has a raised cuticle layer that easily absorbs moisture/chemicals... chemical texture services performed on overly porous hair require a less alkaline texturizer... a lower pH minimizes swelling and helps prevent excessive damage..."
(https://books.google.com/books?id=f6htCgAAQBAJ&pg=PA430&lpg=PA430&dq=milady%27s+standard+cosmetology+porous+hair+res istant&source=bl&ots=G6RzmRDdzk&sig=PDBpMVry4xmF8fHLAVswk4tFoUI&hl=en&sa=X&ved=0ahUKEwiYme3iwoLMAhXLmoMKHR4vAHEQ6AEIGzAA#v=on epage&q=milady's%20standard%20cosmetology%20porous%20hai r%20resistant&f=false)

It also says something interesting about strand thickness & porosity connection (from p. 149):
"Although coarse hair normally has a low porosity and is resistant to chemical services, in some cases coarse hair will have high porosity, perhaps as a result of previous chemical services."

And an interesting test that can be of help (very similar to what Science-y Hair Blog suggests, too):
"You can check porosity on dry hair by taking a strand of several hairs from four different areas of the head (front line, temple, crown and nape). Hold the strand securely with one hand while sliding the thumb and forefinger of the other hand from the end to the scalp. If the hair feels smooth and the cuticle is compact, dense, and hard, it is considered resistant. If you feel a slight roughness, it is considered porous. If the hair feels very rough, dry, or breaks, it is considered highly porous and may have been overprocessed."
(https://books.google.com/books?id=f6htCgAAQBAJ&pg=PA149&dq=milady%27s+standard+cosmetology+porosity&hl=en&sa=X&ved=0ahUKEwjGsp_JxILMAhWEgYMKHcY8DtQQ6AEINDAA#v=on epage&q=milady's%20standard%20cosmetology%20porosity&f=false)

It seems pretty consistent with what Science-y Hair Blog wrote about porosity (http://science-yhairblog.blogspot.ca/2012/06/hair-porosity-how-to-measure-sort-of.html), I don't really see discrepancies. :) I think, some sort of resistance (retaining shape to some degree, repelling water to some degree, resisting mild chemical, environmental exposure, etc...) is natural for non-damaged, "healthy" hair (that's how hair can survive for many, many years despite relentless handling), and that's what cuticles, 18-MEA and other components with barrier function are there for, but they do erode over time due to normal wear & tear and damage (UV, chemical, mechanical, thermal...)... so I guess it's all about the degree of that resistance. :)