Lash Length vs. Strength

There are many ways to decide what sizes of lashes to use on your clients.
However, one method that isn't often mentioned is Hair Strength.
There are so many rules I've seen "Only 2mm longer than NL", or "30% longer
than natural lashes", or "Double the length of the natural lashes or less".
These are all very typical ideals which are taught in most reputable lash
academies (ours included!).
We need to remember, eyelashes are HAIRS. Which means that in the end, it
is the strength and type of hair, NOT the LENGTH which is the determining
factor of what sizes of extensions you need to use.
Think about this! You wouldn't go to your hairdresser and tell her that since
your hair is long, you feel it can handle extreme chemical processing (going
from Black to Blonde in one shot???) would you? NO!
The LENGTH of your hair does NOT equal the
STRENGTH of your hair, and this is 100% applicable to eyelashes.
Just like all hair, there are 3 determining factors that you can consider to determine how strong the hair is
before proceeding.
 Density (amount of eyelashes along the lash line) - take a look at the lash line very closely - would
you say it is Dense (many lashes), Medium (average), or Thin (very few eyelashes)?
 Texture (thickness of individual eyelash strands) - take a look at an individual eyelash hair. Is the
strand Very Thick, Medium, or Very thin?
 Strength (a combined result of porosity and density overall) - Are they Less Porous, Average, or Very
Porous?
The strength of the eyelash hair can be determined in two steps. First, porosity is determined, then
elasticity.
Porosity is the amount of water retained by the hair. Porous hair is generally more damaged, and has a
tendency to absorb more liquid, but it will not retain as much moisture. Hair with low porosity is
considered healthy and resistant, and can withstand stronger chemicals, adhesives and heavier weights of
extensions.
To determine porosity, after eyelashes are freshly washed, blot out excess moisture with a flocked tip
applicator. Then take a clean tissue or Kleenex and blot the eyelash again. Feel your tissue with your
hands, if it feels very dry already, you have low porosity--your lash expels the excess water quickly, it is
"full." If your tissue feels damp or generally wet, you have normal porosity, meaning the hair gives and
takes moisture evenly. If the tissue is still moist after blotting the first or second time then the eyelashes
are taking on too much water, and thus very porous.
Porosity is completely independent of density and texture - You can have Dense, Thick eyelashes and high
porosity, which means they are weaker than they appear.
Elasticity is the final step in the analysis and the part that makes your final determination of the eyelash
strength. This step is very difficult to determine without pulling out a natural eyelash and trying to stretch
it to capacity! You don't want to do that... But what you can do is look closely at the lashes. Do any look
broken? If there are some broken (blunt tipped) eyelashes, they are lowelasticity. None are broken, they
are likely High-Elasticity, however you will want to keep a close eye during fills to make sure the lashes
continue to stay strong without any breakage.