Hell, Is She Leaking Or Not?

The amount of air or let's say the air pressure inside your airgirl is very critical parameter. For perfect performance the air amount has to be tuned up to mililiters. We don't talk about damage of the doll's body now, but about the most pleasant behavior. The perfect value of air amount must hold several hours without change, during one night as minimum, longer duration is better. From this point of view, the problem is any minimal air leak and also influence of temperature and atmospheric air pressure.

Example of barometric pressure prediction - the black line.

Sometimes the airgirl may appear leaky, but it is not. Also, if you try to do some diagnostics to find or identify an air leak, sometimes you have very hard work. It is very difficult to recognize if the air is really leaking or not. The only way to solve is longer time (few days) observation while watching to a barometer and a thermometer. Computerized system with history of measured data or good weather service will help much.

The first problem is the atmospheric or let's say barometric pressure. Your toy will look weaker if the barometric pressure will grow in respect to time when you had inflated your toy. The average barometric pressure at sea level is given as 1013.25 hPa and variation in range 30 hPa around the mean value is normal. In special cases the variation can be several times bigger. The change can be quite fast, 1 hPa per hour is possible. The nice explanation can be found here. Not only airgirls can have headache caused by barometric pressure.

The second matter is the temperature of the air inside your toy. If the toy will stand in constant ambient temperature, it will quickly get the same temperature as surrounding. In the case of exposition from a sun shine or an IR rays from heating, the temperature will grow. The same will work with your body as a source of the heat. If you will take your airgirl into bed, under blanket with you for a longer time than 20 - 30 minutes, you can expect the similar temperature as at your body. The (roughly) 37 degrees is pretty much and you will observe many interesting effects on the air and on the vinyl material. If the toy was not inflated too much, it will not be dangerous for the toy, but it is very pleasant. You will feel a heat reflected from the toy, which is very nice and it make a perfect feel of a live creature next to you.

In our case of very low pressures without any phase changes the air will behave very near to ideal gas. For the influence of temperature we can use simple thing, a Combined Gas Law, dependence between an absolute temperature T, a volume V and a pressure P.

The Combined Gas Law. Relation between the pressure, volume and temperature of the gas.

For simplicity, we will assume the constant pressure. The volume is then interpreted as uncompressed volume, the volume of air, which you will take from atmosphere and put into your toy. This way lets us avoid complex behavior of vinyl. Also, when you inflating your toy, you will know best what every piece of air will do, what is much, what less, ...

Now, we can express special inflatable related parameters which combined both temperature and barometric pressure into one number.

Generic inflatable related coefficient which combined influence of temperature and pressure.

The kname is generic inflatable related coefficient expressed in PROMILE, which says, how much air is over (+) or how much air missing (-) relative to volume of the toy. If you know the volume, you can multiply and you know, how much air has to be added or removed. If you don't know the exact volume of your toy, you can use this number for comparison between times - see the number and know or do.

The expression "name" is used because there can be more variants of k based on generic kname. The P0 and T0 is always the barometric pressure and the air temperature in the time of inflation. The Pa is actual barometric pressure and the Ta is the actual temperature. We can make three variants based on different Ta.

• The kstorage or kstg uses (Ta) to K as room or ambient temperature.
• The klair or kbed uses (Ta) to K as body temperature 37 degrees.
• The koutdoor or kout uses (Ta) to K as outdoor temperature.

Note that T is always absolute temperature in Kelvins and pressure usually in hPa, but there is a relation so there are other pressure units also possible. Promiles are used because of suitable resolution and number format. You can look to our Hannah Matrix computerized system how the history of inflatable related coefficients look. The system is still under development and many updates will be applied in future, but it is interesting, I think.

What Is iIside Our Toys?

When you look into transparent inflatable toy or into common inflatable toy through the valve - you will see ... nothing. Clear transparent medium the same as surrounding us on the Earth. The very small difference is in count of molecules in unit volume inside with respect to outside, which results in a force on the toy's wall from inside. This force give the shapes we like so much. The force is distributed amazingly equally over all the surface. This brings the unique pleasant touch. Another magical property of our toys.

How do you fill your toy? There are several methods, which people often speak about. All method needs it's own special tools and have special properties.

• Hand pump or foot pump - one of the best devices for filling your toy. There is nothing which we need to afraid as potential danger for toys, if you keep the final air pressure low.

• Electric pump (turbine, as in vacuum cleaners, air beds) - this method is the fastest, while there is not dangerous pressure achievable. You will need an electric power of 230V AC (only few pumps have accumulator or 12V car network input). The engine of these pumps us usually a terribly noisy. You will need ear protection or suitable electronic speed regulator. One my friend, who care about his toys perfectly, considered the ozone O3 produced by sparks in motor as dangerous. Ozone is strongly oxidizing gas.

Electric quick pump in DIY frame with speed regulator and frame ready for noise damping.

An example of electric pump speed regulator. Taken from HYUNDAI vacuum cleaner.

• Compressor - quite ineffective to dangerous method. Compressors usually produces smaller amount of air and very dangerous pressure which can shred your toy in pieces. Common compressors use oil for lubrication which can be present in output air as aerosol. There are filters for oil removal, but not always reliable as we need. The oil will destroy plasticizers and thus your toy. Big noise and power consumption is apparent.

• Your lungs and mouth - classic, the most magical method, due to big contact with your toy. You can say you breath life into your toy. On the other hand, this method can be designated as most dangerous. The air from lungs contains bigger amount of moisture, which will condensate inside the toy, when air is cooled down from body temperature to ambient. Water in toys can result in bacteria and mold growth after some time inside. Cleaning is very difficult and sometimes the products of life inside can damage the material. After time you will find some seams very weak, vinyl material will have plastic deformation instead elastic, etc. Also, some oil from your lips remains on the valve and it make it crumble after time. You can replace it, but it will not be original then.

• Bag pump - there is another strange method, absolutely without any danger. i don't know, but there may exist a patent for it. You can take a plastic bag, it may be a trash bag and put a nozzle on closed end or into corner. Then you can catch air into bag, close it by your hand and blow into toy through the nozzle. Very fast, and with smallest tool needed.

The bag pump full of air. Ready to fill your toy.

Folded bag pump in comparison with a credit card case.

Note about ozone - would it be possible to see small amount of ozone inside the inflatable toy as beneficial? Maybe it will not damage the vinyl or plasticizer, but it will sure destroy possible bacteria and molds? Who know.

Note about mouth inflation - maybe you heard about danger for people, from plasticizers contained in older inflatables and thus in air valves. There are laboratory tests done when amount of several plasticizers is measured, etc. I say - DON'T BELIVE BULLSHITS. There are a commercially motivated trends - phtalate free (big) toys, lead free soldering, no mercury thermometers, no tungsten bulbs, ... STOP!!! We are not talking about children dummies here. I and many people of my age grown surrounded by "dangerous" things and there is not any problem with it up to now. There are many worse modern problems today.

Sign, which some manufacturers used to say - mounth inflation of our product is safe.

Before longer time, few guys on Dollforum talked about use of nitrogen for filling blow-up dolls instead of air. One said, that this is very good for tyres, because nitrogen N2 have bigger molecules and possible leaks are lower. Second guy replied, that there is danger, when the doll will burst in your bed. You will be exposed to nitrogen. It is interesting, but what is the air? It consists mostly (approx. 78%) from nitrogen, there is better explanation. The use of pure nitrogen will not have any effect for leaks. Also, if the doll will break, you never will be exposed into clear nitrogen. You will not suffocate. But why to use the nitrogen for tyres? Because it is perfectly dry. Lower moisture will make degradation of your tyres lower, lower corrosion of metal wires inside, etc. Tyres are exposed to much higher stress, pressure and especially thermal swing, so lower moisture inside can make them good.

Note about nitrogen inside inflatable toys - if nitrogen have bigger molecules, than other components of air, what will happen, when you fill your toy with air and left for a long time? The relative amount of nitrogen will grow, because other components will fade out. It will work as a special filter. Isn't it?

The very big attention has to be paid on the pressure. More pressure will make your toy life shorter. The perfect pressure is that, which gives your toy feel like a fluffy heap of cotton when touched. Also, you must see a wrinkles on edges. At inflatable dolls, when you take her in arms, her legs and arms must hang down. It is not saddest thing, than toy damaged by much air. There will be many leaks which are very hard to find, deformed shapes... Try to imagine stress to inflatable toy as a multiple of air pressure and external force onto (from your body for example).

This picture shows how inflate the toy properly. No shape distortion, long wrinkles, soft to touch.

Roughly we can say, that the force applied on the seams and on the vinyl surface depends on air pressure and on diameter of inflated shape. In real complex shapes there are also more complex dependencies. Good manufacturers inflate their toys after welding and expose them to (well regulated) warm air. Then the vinyl will stretch and tensions in stressed parts are released, forces will be distributed better. These toys are much more durable. Similar effect can be observed in real use. In warm weather, there will be less seam split failures than in cold, because vinyl is softer and tension is well distributed.

When the toy is tressed and then released, you can see it a bit deflated. This is NOT good time for adding some air. The toy is not deflated, but the vinyl is temporary stretched a bit. Wait a minute and it will contract back to state before stress, Adding air in this situation increases the pressure and leads to permanent damage of your toy.

So inflate gently and get more from your toys!