When you fill a tank, one thing you have to be sure of is that the tank is enclosed so none of the liquid splashes out or evaporates. Since evaporation is always a concern, the tank should be insulated by either providing multi-layered walls or placing the tank under ground. For an enclosed tank, the heat of evaporation comes in two forms, diurnal (night to day) temperature changes or by seasonal changes (i.e. spring to summer). A common method of preventing evaporation for above ground double walled tanks is by painting the outside white, to reflect the sun's rays. No matter how much the tank is insulated for some liquids, evaporation, or the term I use, "vapor growth" should be expected so a good tank design always includes a means to reroute and condense any vapors that form.
When filling the tank, you have to be careful how you fill the tank with fluid. Typically, the tank design will provide for a filling tube (called a submerged fill pipe) that begins at the top and terminates at nearly the bottom (standard specification is 6"). The reason for this, is that fluids will create vapors if allowed to just dump into the container. The filling should be done in what engineers call, laminar flow, or the steady easy flow causing very little mixing or aeration. The type of flow that causes mixing is called turbulent flow. A combustible liquid flowing in turbulence can be very dangerous. A certain amount of ullage should also be provided for vapor growth and without ullage, the combustible liquid can also be very dangerous. Another means to prevent turbulent flow is by filling the tank from the bottom, or "bottom filling" and gravity and the weight of liquid provides for the slow and steady filling of the tank.
So how does this relate to Magick?
I think that when you learn magick, its sorta like understanding the properties of a fluid to be placed in a tank. You learn how well it flows, any toxins that may be associated with it, and if it causes any problems, like combustion. As magicians, we should spend a great deal of time, just learning the craft and getting an understanding of what the magick is about, before we allow ourselves to let the magick begin to fill the vessel, or the "tank", of our bodies. The combustible liquid and the flow, or the "magick" becomes the active part and the container becomes the "passive" part, two very essential parts of our Will.
One of the very basic tenets for CM is learning the Lesser Banishing Ritual. We learn to control the fluid flow of the magick and introduce the magick within our bodies in a straight and narrow path, as in the idea of pulling the Divine energy from the interface at Kether to Malkuth ("ATAH-MALKUTH"). The flow of magick is like the fluid flow within the submerged flow pipe. Magicians control the path of the magick, because, like the fluid, any other way would cause loss of the precious fluid. We cannot allow the magick to simply dump within our bodies.
The creation of the quarters and circle become your body's insulated and multi-layered walls and the purity one brings to the body is like painting your above ground tank white to reflect the sun's rays. (As an aside, I think that the purity we bring forth is through the means of healthy eating and exercise.) Since some tanks are placed underground to provide for insulation, I think this notion is a good metaphor of why grounding our practices within such subjects such as herbalism, gemology, metal-working, the martial arts, fine arts and the performing arts are so beneficial. Working with these arts in the material realm become our multi-layered insulated walls: grounding (as in an underground storage tank) the magick in the Earth, providing another means to capture the active part of our Will, setting boundaries for our experiences and allowing us a way to define our Will.
Cyclical temporal temperature increases, as in day to night or spring to summer, or the way I see it, the issues and challenges we encounter during normal everyday life (diurnal) and getting older (seasonal), are to be expected. I think the grounding practices/arts or the insulated/purified walls we create provide for stabilization that may cause us to lose the precious fluid of magick. It becomes our solace, a means of expression, yet nurturing and protective.
But like I said, a good tank design always includes a means to reroute and condense any vapors that form. If we were gurus living in meditation and prayer on a mountain, we do not need to expect many effects on our Will, as in the Heat of Evaporation or vapor growth. The magick simply pours into our Being, slowly and steadily, without many interruptions and cannot be affected by the Heat of Life...But unfortunately, most of us are not gurus on a mountain and we have to deal with the struggles and issues of day-to-day Life. I think, and I am agreeing with Dion Fortune on this, the Western Mystery traditions were established because the West needs a means to capture the magick or become enlightened, despite our needs to make a living, raise families and be part of a social culture. I think the grounding practices or arts... and especially alchemy... besides being a solace or our passion...provides for the very necessary means to reroute and condense the fluid of our magick. These practice becomes our bottom filling, the steady devotion of time and learning stabilizes us, like gravity.
Do I think our Will is like fire? No, on the contrary, I think our Will, both the active and passive elements are more like a combustible liquid within a tank and the liquid exhibits the same behaviour properties as water: taking the shape of its container, requiring containment, insulation, means for steady/easy flow and a way to re-route/condense. The Will is the fluid, the flow and the container.
What are the dangers of a combustible liquid that I was alluding to? What happens if one allows the liquid to overfill or become turbulent? What happens if we add too much of a spark of Fire, without understanding the properties of Will?