Hello there, just passing by to clear this up.
A good analogy to understand this, would be to compare stromlight to heat. Let's be honest, stromlight is nothing like heat (heat is not a gas, it's just energy. And stormlight may be energy who has taken the form of a gas, which is weird), exept for one thing :
Heat moves from hot areas to colder ones until both areas are at the same temperature. Like when you're outside and naked when it's cold : your body temperature gets lower and lower, and if you stay too long outside, you'll freeze to death. That's because the membrane (your skin) is not perfect and allows heat to leak off your body to get outside on amazing adventures.
Add something a bit harder :
Some materials have a higher conductivity (i don't know if this is the exact term, i'm not a native speaker) than others. Conductivity is the capacity of a material to conduct heat (no rust, sherlock).
Heat transfer occurs at a lower rate across materials of low thermal conductivity than across materials of high thermal conductivity. Materials of high thermal conductivity are widely used in heat sink applications (sucking heat out of something, think systems to cool down something) and materials of low thermal conductivity are used as thermal insulation. The reciprocal of thermal conductivity is called thermal resistivity.
Now let's look at Stormlight.
There goes the cycle : an Hightstorm comes, infuse gems with stormlight. When Stormlight is stored somewhere, it leaks off. Stormlight in a gem : it leaks off. Stormlight in a Knight : it leaks off. The light leaks because the "membrane" is far from perfect : There is no insulation between the air and the gem. The Stormlight goes from the gem to the air because the permitivity of the air is higher than the gem. It's physically "easier" for the stormlight to be in the air than it is in the gem. It's a kind of gas, and gas have the tendancy to expand to fill all the volume they can.
Add conductivity : with the Heat, your knight would be the steel handle : fast to leak off once it's charged because the skin is too imperfect to hold Stormlight. Plus breathing out leaks a toncrap of light.A Knight in a true Shardplate might be better.
The gem is the wooden handle : once infused it's slow to leak because the insulation between the center of the gem where most of the light stands swirling and the outer rim where the light leaks is very good.
ie to hold stormlight on a long time without using it: gem > Shardplatted Knight > Knight.
Now, we add the capacity of a Surgebinder to breathe in and out Stormlight. With heat, the analogy is Convection, ie transfert of heat by moving particules. Think of water :
Forced convection is the act of forcing the movement of particules to speed up the process. Think of a climatisation coupled with a fan : it's more effective that just a bloc of ice sitting in the room.
When a Surgebinder breathe in Stormlight, he forces the transfer of energy from the Gem to his body. It is a faster process than if the gem was just leaking into the air.
