There are few things more disappointing than a party decorated with underinflated balloons. I don't know about you, but when I inflate balloons, I want to get the most for my dollar. Balloons that are not fully inflated aren't the right shape or the right color, and never have the shine that properly inflated balloons do (see Rubber chemistry for why).
For many people, inflation is a big part of the fun of a balloon. It is exciting to blow up a balloon as big as you can without popping it.
So no matter your particular interest in balloons, perfect inflation is the most important tool available to you.
Levels of inflation
First of all, let me offer a quick visual inflation guide. I'll refer to these levels of inflation as I continue. These three pictures are all the same balloon: a 12" Unique.
This balloon is clearly underinflated. Note the round shape and long uninflated neck. It's also not very shiny. Not useless though: games that require sitting or stomping on balloons to pop are made more interesting by underinflated balloons. Crushing an underinflated balloon will displace air into the uninflated neck portion, and most of the time, the balloon can redistribute its stresses without popping. This is a fully-inflated balloon--not underinflated, not overinflated. The right size for most games and decorations. Full inflation is defined as the point at which it becomes preferable for the neck of the balloon to take any additional air, rather than the round "bulb." This gives rise to a tear-drop shape. One less blow, and the balloon is underinflated; one more, and a neck will form. The balloon begins to feel tight to the touch. For those who enjoy an occasional thrill, balloons can be overinflated like this one. Many balloon enthusiasts won't tie a balloon unless it has so little neck left that it's nearly impossible to do so. Note how shiny this balloon has become and how long the neck is. The balloon is very tight and may ring when tapped. New balloons inflated to this stage (if they make it this far) are sometimes unpredictable and can spontaneously pop.
Inflation falls into several stages-- which can be described as distinct regions on the balloon's stress-strain curve (see Balloon physics): stretching, constant-volume blowing, constant-pressure blowing, neck inflation, and overinflation. The description I'll give relates mainly to round balloons-- airships and other shapes are not that different, but they (usually) lack an appreciable neck to speak of.
A new balloon should be stretched several times before attempting to inflate it for the first time. Stretch the balloon once lengthwise and once crosswise-- just grasp it between your fingers and thumbs and give it a good tug or two. Finally, stretch the neck of the balloon a couple times.
Put the lip of the balloon between your own lips (between your teeth if you need) and blow. The breath should originate from the lungs and have the force of your diaphragm behind it. Don't puff out your cheeks, keep them tight. This inflation stage involves blowing up the balloon to a point where the uninflated balloon snaps "to attention" but does not begin to stretch yet. For round balloons, the transition from this stage to the next is very easy. However, balloons like 260s are notoriously difficult to inflate at this stage.
Once adequate pressure builds up in the unstretched balloon, it begins to stretch and expands at a constant pressure as you blow more air into the balloon. As you blow, keep an eye on the drip point (the thick portion opposite the neck) and keep a hand on the balloon's side to gauge how tightly stretched it's becoming. And if you're inflating a large balloon, be careful not to pass out! Continue blowing until the balloon tightens underneath your hand, or until the drip point becomes small enough. Also, watch the neck of the balloon-- when the neck first begins to inflate, you'll be able to tell. Move on to the next step when this happens.
At this point, you may stop and tie your balloon-- this is the full-inflation stage, defined as the point at which the balloon's neck first inflates. To take the balloon to overinflation, the rest of the neck must be inflated. Caution: overinflating a balloon can be an unpredictable process. For your protection, it is advisable to wear protective eyewear. A pair of sunglasses or goggles will work.
First, stretch the balloon's neck a few times. It works best if, rather than pinching the neck with both hands, one hand tugs the rolled lip while the other lightly squeezes the inflated portion of the neck. After stretching the balloon's neck several times, slowly blow more air into the balloon. The neck will inflate toward your lips. With your free hand, continue to test the tightness of the balloon's body as you inflate. See below for more neck tips.
If at any point the balloon becomes significantly more difficult to inflate, stop and tie the balloon off-- it is as inflated as it is going to be. If you still want a bigger, tighter balloon (or if you're taking this balloon "all the way" so to speak), continue with extreme caution. Otherwise, tie the balloon off and put it to use.
The balloon will now be much more difficult to inflate, especially so with larger balloons (24" and larger are the most difficult). Often, the neck is inflated so completely that holding the balloon between your lips will be next to impossible. This is the point of the stress-strain curve at which the balloon does not expand any further but gets tighter (constant-volume and increasing pressure-- the vertical area of the stress-strain curve). A balloon inflated this far can pop at any moment, so if you decide to blow any more air into the balloon, do so with caution.
This guide works well as a walkthrough, but remember that each balloon is different-- some balloons are thin enough that their tightness is never established; some contain synthetic rubber making them harder and tighter sooner than balloons made with 100% natural latex. The best way to figure out how a balloon will behave is to just inflate one as a trial and see what develops.
As far as balloons popping during inflation, it is a very rare occurrence, especially with higher-quality brands. At one extreme, there are brands that are of sufficiently high quality to have only one defective balloon per gross, or less; at the other, there was once a bag of airship-shaped balloons I bought in which none of the balloons inflated past halfway without popping. They were drug-store balloons however; if you stick to major, reputable brands, you'll not have to worry too much.
Usefulness of different inflation levels
Don't ever let me catch you decorating with underinflated balloons, heh heh heh... but they can be of use. In any balloon game requiring sitting, stomping, or otherwise crushing balloons until they pop, underinflated balloons can make the game much more challenging. Due to their large uninflated neck, they can take a lot of abuse and simply transfer any displaced air into the neck, making them very hard to sit-pop or stomp-pop. For any other purpose, however, do yourself a favor and inflate at least to the full size. Fully-inflated balloons are truly multipurpose. They're just the right size or shape to decorate with, play with, or pop by whatever means you wish (quality balloons can take quite a lot of abuse, even at full inflation-- you'd be surprised). Especially for decoration, make sure your balloons are at least this full-- it brings out the color and shine of the balloon just as the manufacturer intended. Balloons that have been "necked-up" or overinflated are great fun to have around. Try using them in any balloon game in which popping balloons is undesirable-- these balloons make it hard not to pop them if subjected to rough handling. Because of their mirror-like shine, feel free to use overinflated balloons to decorate-- just be sure the room doesn't get too hot, because often these balloons are just looking for an excuse to pop when you least expect. And if you ever do a small balloon drop at a party, or any other decorating that involves loose balloons laying around the floor, try overinflating them. These balloons are likely to be popped during the party anyway, so might as well have them as big as they can be before they do! There are also safety reasons to overinflate balloons occasionally: when doing a balloon drop, you have to expect people to be stepping and jumping on the balloons to pop them. So make sure your balloons are at least fully inflated, if not overinflated. If you do a drop with underinflated balloons, people might step on the balloons and slip if the balloon doesn't pop. You don't have to neck-up the balloon all the way like this one, but at least try for some neck.
Inflation of Figurine Balloons ;-)When they are all the way up, figurine balloons have lots of personality! But, they need proper handling to get all the way up.
Figurine balloons have multiple sections, usually with a different diameter for each section. It takes more pressure to inflate smaller diameter sections of a figurine balloon than to inflate its larger diameter sections. So, if one first inflates a larger diameter section of a figurine balloon, the additional pressure needed to inflate or fully inflate a smaller diameter section often POPS the larger section before the smaller section is up. ;-(
Specifically, the pressure difference (between the inside and the outside of the balloon) that is needed to inflate each section, as well as he pressure difference that is needed to POP each section, are inversely proportional to the diameter of that section. For example, inflating a smaller section that is one half (½) the diameter of a larger section, requires two (2) times as much pressure difference. If one first inflates the larger diameter section of such a figurine balloon, and then increases the pressure difference by a factor of two, so as to inflate the section with half the diameter, the larger section will often POP! But, there is a solution. ;-)
Once a section of a balloon has been inflated, that inflated section now has a larger diameter. Because of the now-larger diameter, it takes less pressure to keep that inflated section up than it took to inflate it in the first place.
In addition, if a section of a balloon has been pre-inflated and then deflated, it will take less pressure to re-inflate that section.
So, the general strategy to fully inflate a figurine balloon is to start by pre-inflating only the smallest diameter section(s) and, then, let the air out. If there is a significant difference in diameter, one may need to pre-inflate the smallest diameter section(s) a few times, or to keep the pre-inflated section(s) up for several minutes before deflation.
After releasing the air from the pre-inflation, fully inflate the smallest diameter section(s) first, until it is (they are) hard and tight. Then continue inflating, allowing the inflation to migrate into the larger diameter section(s). Do not let the larger diameter section(s) suddenly expand and suck air from the inflated smaller diameter section(s). This progressive inflation will result in all sections’ of a figurine balloon being fully inflated. ;-) But be careful; when he's all the way up, the figurine is easy to POP! ;-(
The most challenging-to-inflate figurines are the Czermak & Feger “Gummiwerk” GIANT BUNNYs. These balloons have five different sections. There are three sections of small diameter, namely two ears and a tail. There is a head of medium diameter. Finally, the body has a large diameter. To fully inflate these balloons, start by pre-inflating the ears and tail only. A good rule of thumb is to pre-inflate the ears three times and to pre-inflate the tail six times. Alternatively, one may instead leave the small sections up for a period of time during pre-inflation. Do not pre-inflate the body or the head.
After releasing the air from the pre-inflation, begin the full inflation by fully inflating the ears until they are hard and tight. After the ears get hard and tight, continue inflating and allow the new inflation to migrate into the head. Be careful not to let the head suddenly expand and suck any air out of the ears.
After the ears and head get hard and tight, continue inflating and allow the new inflation to migrate into the body. Again be careful not to let the body suddenly expand and suck any air out of the ears.
After the body gets hard and tight, stretch the end of the tail away from the body as you try to squeeze some air from the body into the tail. Stretching the tail allows the tail to inflate more easily. If the tail does not form, blow in a couple of small breaths, and again stretch the tail as you try to squeeze air from the body into the tail. Repeat blowing in a couple of small breaths, then stretching the tail as you try to squeeze air from the body into the tail, until the inflated tail forms. ;-)
Typically, about two thirds (2/3) of the tail will inflate before expansion stops and the balloon gets harder to blow into. At that point, the bunny can’t take any more air. If you continue to blow him, he will POP! ;-(