Storage: case, temperature, humidity
A rubber cleaned after the session — following the routine described in 13.5 — can lose in a week what the cleaning has preserved if the bat is stored badly. Storage does not improve equipment, but careless storage degrades it without the player touching a ball. The enemies are few and well known: heat, humidity, light and mechanical pressure.
The case is the first barrier. Its function is not decorative: it isolates the bat from airborne dust, from knocks in transit and, if it is of reasonable quality, from abrupt changes of temperature. Hard or semi-rigid cases protect against impacts better than soft fabric ones, but any closed case meets the minimum: keeping the rubbers out of the open air and out of direct light. Carrying the bat loose in a rucksack, with the rubbers rubbing against keys, bottles or damp clothing, is the most efficient way of shortening its life without playing at all.
Temperature is the factor that does the most damage with the least warning. The rubber of the topsheet degrades through oxidation, and heat accelerates that reaction. A bat forgotten in a car boot in summer can reach temperatures that in an hour cause more ageing than a month of normal use. The sponge suffers too: it loses elasticity, hardens, and the catapult effect described in 2.4 is attenuated irreversibly. Extreme cold is less damaging but not harmless: a rubber taken from a very cold environment and put straight into play behaves more stiffly until it reaches room temperature. The practical benchmark is simple: a bat is stored where a book would be stored, at room temperature, away from direct heat sources and from windows in the sun.
Humidity attacks from another flank. Wood is hygroscopic: it absorbs and releases water according to the environment. In very humid conditions the outer plies swell slightly, can warp, and the bond between blade and sponge weakens. In very dry conditions the wood contracts and can generate stresses that cause micro-cracks in the varnish or in the structure itself. Neither extreme is common in an ordinary home, but changing rooms with showers, unventilated cellars and sports bags closed with wet kit inside certainly are. Where a bat has been exposed to high humidity, it is worth leaving it to air-dry — out of its case, but away from the sun — before storing it again.
Position matters less than some players believe, but it has one relevant point. If the bat is stored with weight on top or resting on one rubber for weeks, the sponge can deform permanently in the contact area. The effect is small where the pressure is light — the bat simply lying flat — but it is accentuated where books, rackets or bags are stacked on top. The simplest approach is to store it horizontally inside its case with nothing on top, or upright if the case allows. The protective films mentioned in 13.5 for tacky rubbers serve a second function here: they stop the two rubbers coming into direct contact if the case is soft and the faces touch.
None of these precautions demands effort or expense. A case, a cool dry place, and the habit of not leaving the bat where a precision instrument would not be left. The degradation these habits avoid is the same one later mistaken for “worn” rubbers or “dead” blades — signs detailed in 13.7 and 13.8 — when in fact the equipment has aged off the table, not on it.